OBD:SNDD: Difference between revisions

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m (→‎.raw part (MS ADPCM, PC demo): minor correction. Heading towards a complete rewrite of this thing.)
(ok, there it is)
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:''For metadata instances used to group sounds together, randomize them, adjust their volume or frequency, etc, see [[OSBD]] and its subtypes: [[OSAm]], [[OSIm]] and [[OSGr]].''
:''For metadata instances used to group sounds together, randomize them, adjust their volume or frequency, etc, see [[OSBD]] and its subtypes: [[OSAm]], [[OSIm]] and [[OSGr]].''
SNDD instances is where Oni stores sound data. Sounds can be either mono or stereo waveforms (with sampling frequencies of either 22.05 kHz or 44.1 kHz), and they are typically compressed to save on storage space. Both the PC and Mac versions use a form of [[wp:ADPCM|ADPCM]] compression (Adaptive Differential Pulse-Code Modulation), where 16-bit sound samples are encoded as 4-bit "nibbles" (resulting roughly in a 4:1 compression ratio as compared to uncompressed 16-bit [[wp:PCM|PCM]]).
SNDD instances is where Oni stores sound data. In Vanilla Oni game data, sounds are either mono or stereo waveforms (with sampling frequencies of either 22.05 kHz or 44.1 kHz), compressed to save on storage space. Both the PC and Mac versions use a form of [[wp:ADPCM|ADPCM]] compression (Adaptive Differential Pulse-Code Modulation), where 16-bit sound samples are encoded as 4-bit "nibbles" (resulting roughly in a 4:1 compression ratio as compared to uncompressed 16-bit [[wp:PCM|PCM]]).
*On PC (both retail and demo), sounds are encoded using Microsoft's ADPCM algorithm described [https://wiki.multimedia.cx/index.php/Microsoft_ADPCM HERE]. [[wp:FFmpeg|FFmpeg]] lists this codec as '''adpcm_ms'''.  
*On PC (both retail and demo), sounds are encoded using Microsoft's ADPCM codec (implemented in [[wp:FFmpeg|FFmpeg]] as '''adpcm_ms'''). See [https://wiki.multimedia.cx/index.php/Microsoft_ADPCM HERE] for a quick description.
*On Mac, sounds are encoded using the IMA4 algorithm described [https://wiki.multimedia.cx/index.php/Apple_QuickTime_IMA_ADPCM HERE]. [[wp:FFmpeg|FFmpeg]] lists this codec as '''adpcm_ima_qt'''.
*On Mac, sounds are encoded using QuickTime's IMA4 codec (implemented in [[wp:FFmpeg|FFmpeg]] as '''adpcm_ima_qt'''). See [https://wiki.multimedia.cx/index.php/Apple_QuickTime_IMA_ADPCM HERE] for a quick description.
;Key shortcomings of the PC demo and Mac SNDDs as compared to PC retail SNDDs:
 
*PC demo and Mac SNDDs have a "short" .dat part that specifies only the frame count (animation length in game ticks) and number of channels (mono or stereo). The waveform data is always assumed to be sampled at 22.05 kHz, and compressed into 4-bit ADPCM (either IMA4 or MS ADPCM).
As a unique feature of Oni game data, SNDD files have a significantly different structure depending on the engine version. For PC retail (.dat/.raw storage, no .sep files), the SNDD files are larger and include a 50-byte chunk of data that is equivalent to the "fmt " chunk of a WAVE file. For the other two versions (PC demo and Mac, .dat/.raw/.sep storage), this 50-byte block is missing. It turns out that the extra format data allows the PC retail to support both MS ADPCM and IMA4, as well as uncompressed PCM, whereas PC demo and Mac engines only support MS ADPCM and IMA4, respectively. (It has not been confirmed whether the PC retail engine supports other WAVE formats beyond PCM and MS ADPCM, such as Mu-Law or A-Law PCM, IEEE float PCM, etc.)
*PC retail supports arbitrary sample rate, which allows for crisper high frequencies: specifically, 44.1 kHz (CD quality) is used for the 46 electric spark sounds '''ap_hit_shld''' and '''zap##'''. Possibly PC retail supports uncompressed PCM waveforms as well.
----
; Key shortcomings of Mac SNDDs as compared to PC SNDDs (both retail and demo):  
For clarity, the simpler and more straightforward SNDDs of PC demo and Mac are documented first, followed by the more complex and versatile PC retail SNDDs.
*At 22.05 kHz, the storage size of Mac SNDDs (IMA4) is about 5% larger than for PC equivalents (MS ADPCM), because of a much smaller block size in the .raw part (the smaller .dat part of Mac SNDDs doesn't help).
:(Historically, though, the PC retail implementation is older, and the PC demo and Mac versions were trimmed-down iterations of PC retail.)
*Mac SNDDs have encoding/editing artifacts at the ends of looping segments (music and ambient tracks). PC SNDDs (retail or demo) have no such artifacts and allow nearly seamless playback. See [[OBD:SNDD#Looping_issues|BELOW]] for details.
 
==Oni storage==
==Mac and PC demo==
===PC retail===
The below example was taken from Mac Oni. In PC demo the file would look the same, except for possibly different res_id (at 0x00) and smaller raw data size (at 0x10).
 
[[image:sndd_alm.gif]]
 
{{Table}}
{{OBDth}}
{{OBDtr| 0x00 | res_id  |FF0000| 01 D6 08 00 | 2262      | SNDDcomguy_dth2.aif, instance number #2262 }}
{{OBDtr| 0x04 | lev_id  |FFFF00| 01 00 00 06 | 3        | level 3 }}
{{OBDtr| 0x08 | uint32  |FFC8C8| 01 00 00 00 | 1        | flags
:1 - (compressed; always the same in Vanilla Oni)
:2 - stereo (mono if disabled) }}
{{OBDtr| 0x0C | uint16  |FFFFC8| 37 00      | 55        | duration in 1/60 seconds (game ticks) }}
{{OBDtr| 0x0E | uint16  |FFFFC8| 00 00      | 0x0000    | padding (unused in Vanilla Oni) }}
{{OBDtr| 0x10 | uint32  |C8FFC8| 5E 2A 00 00 | 10846    | size of the part in the raw file, in bytes }}
{{OBDtr| 0x14 | offset  |C8FFFF| 00 B1 01 00 | 0x1B100  | at this position starts the part in the raw file }}
{{OBDtr| 0x18 | char[8]  |FFC8FF| AD DE      | dead      | 8 unused bytes (padding; not part of the SNDD file) }}
|}
;Padding
:The 8 bytes at the end are ''not'' part of the SNDD template. They are not loaded by the Oni engine.
:The uint16 at 0x0E ''is'' loaded by the engine, and thus constitutes a potentially useful 16-bit field.
;Duration
:The duration (number of game ticks) is rounded to the ''lower'' value (a.k.a. "floor") in Vanilla Oni data.<ref name="ticks">As an example, on PC (both demo and retail), '''SNDDmus_ot7.aif''' consists of 152360 samples, which at 22.05 kHz corresponds to 6.90975 seconds, or 414.585 ticks; the duration, however, is indicated as 414 ticks and not 415. In other words, "duration" corresponds to the number of ''whole'' game ticks spanned by the sound's playback.</ref> In other words, it indicates the number of ''complete'' game ticks spanned by the sound's playback.
;Compression
:The effect of the "1" flag (or rather of its absence) is different in the PC demo and Mac engines.
:*On Mac, the flag seems to have no effect at all (the .raw data is still passed to the IMA4 decoding algorithm even if the "1" flag is missing).
:*On PC demo, a missing "1" flag causes playback to fail.<ref>If a SNDD misses the "1" flag ("compressed"), the PC demo engine ''does'' identify the stream as already uncompressed (PCM samples) and skips the initialization phase of the decompression routine, but then proceeds with decompression anyway, and immediately stops because of zero input size.</ref> If the sound is part of a looping permutation, the game crashes (because playback keeps failing on the same sound, over and over).
:The bottom line is that, both for PC demo SNDDs and for Mac SNDDs, the "1" flag should always be set.
The compressed storage of .raw data is described in the following two sections.
===IMA4 ADPCM .raw data (Mac)===
''For an overview of the IMA ADPCM algorithm and IMA4 header (if interested), see [https://wiki.multimedia.cx/index.php/Apple_QuickTime_IMA_ADPCM HERE]. For an actual implementation example, see, e.g., [[wp:FFmpeg|FFmpeg]].''
:The IMA4 ADPCM stream data (stored in the .raw file) consists of 34-byte blocks (in the case of stereo, there is an even number of such blocks, with Left and Right blocks interleaved).
:The first two bytes of each block form a header that sets the initial predictor (upper 9 bits) and step (lower 7 bits) for decoding the block's samples. Typically they are used only for the first block, or for sudden changes of the waveform's value range.
:The other 32 bytes consist of 64 samples stored as nibbles (half-bytes). In the case of stereo, all the nibbles in a block belong to the same channel (either all Left or all Right).
:All the 32-byte blocks must be stored in their entirety, meaning that the overall sample count of the waveform is a multiple of 64 (this is a major difference from MS ADPCM storage in PC retail and PC demo, where the final block is truncated after the last actual sample).
:For this reason, identical sounds do not have the same sample count on PC (both retail and demo) and on Mac. As an example, here are the stats for the main menu music:
{{divhide|Main menu music a.k.a. "Oni Trailer"}}
{|
|
{{Table}}
!SNDD name (and frame count)
!PC (retail and demo)
!Mac
!difference
|-
|
:'''SNDDmus_ot6'''
:415 frames = 6.9166667 seconds
:~= '''152512.5''' samples (@ 22.05 kHz)
|
:0x25B0C = 154380 = 150x1024 + 780 bytes
:= 150x1012 + 768 = '''152568''' stereo samples
:= 6.919183673469388 s (@ 22.05 kHz)
|
:0x27940 = 162112 = 4768x34 bytes
:= 2384x64 = '''152576''' stereo samples
:= 6.919546485260771 s (@ 22.05 kHz)
|
:As compared to the PC version of the SNDD,
:the Mac version has 8 extra samples at the end
:(i.e., the last 4 bytes of the last two blocks).
|-
|
:'''SNDDmus_ot7'''
:414 frames = 6.9 seconds
:~= '''152145''' samples (@ 22.05 kHz)
|
:0x25A3C = 154172 = 150x1024 + 572 bytes
:= 150x1012 + 560 = '''152360''' stereo samples
:= 6.909750566893424 s (@ 22.05 kHz)
|
:0x27874 = 161908 = 4762x34 bytes
:= 2381x64 = '''152384''' stereo samples
:= 6.910839002267574 s (@ 22.05 kHz)
|
:As compared to the PC version of the SNDD,
:the Mac version has 24 extra samples at the end
:(i.e., the last 12 bytes of the last two blocks)
|}
|}
{{divhide|end}}
 
===MS ADPCM .raw data (PC demo)===
''For a detailed overview of the ADPCM algorithm (if interested), see [https://wiki.multimedia.cx/index.php/Microsoft_ADPCM HERE]. For an actual implementation example, see, e.g., [[wp:FFmpeg|FFmpeg]].''
:The MS ADPCM stream data (stored in .raw) consists of 512- or 1024-byte blocks (512 bytes for 22.05 kHz mono, 1024 bytes for 22.05 kHz stereo)
:Each block starts with a 7- or 14-byte header (7 bytes for mono, 14 bytes for stereo), which includes the 16-bit values of the block's first two samples.
:The remaining 505 or 1010 bytes of each block consist of nibbles (half-bytes), each coding for a sample. In the case of stereo, Left and Right nibbles are interleaved.
:Thus the block has room for 1010 samples encoded as nibbles, and the total number of samples per block (including the header) is 1012, be it for mono or stereo 22.05 kHz.
:For space efficiency, the MS ADPCM stored in .raw deviates from the standard, in that the final block is truncated after the last actual sample. In a WAVE file, ADPCM blocks are stored in their entirety, and the actual sample count is specified in a "fact" chunk. In Oni there is no such thing, instead the actual sample count is inferred from the block size and truncated raw data size.
 
==PC retail==
Below is the .dat file part used in the PC retail version.
Below is the .dat file part used in the PC retail version.
<!--
{|cellpadding=3 cellspacing=0 style="line-height:13px"
{{HexRow|0x00|
|52|49|46|46|4E|0C|01|00|57|41|56|45|66|6D|74|20|
|FF|FF|FF|FF|FF|FF|FF|FF|00|00|00|00|00|00|00|00|
|00|00|00|00|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|
|00|00|00|00|00|00|00|00|00|00|00|00|FF|FF|FF|FF|
|RIFF P°°WAVEfmt
}}
{{HexRow|0x10|
|32|00|00|00|'''''02'''''|'''''00'''''|'''''02'''''|'''''00'''''
|'''''22'''''|'''''56'''''|'''''00'''''|'''''00'''''|'''''27'''''|'''''57'''''|'''''00'''''|'''''00'''''|
|FF|FF|FF|FF|FF|FF|C8|C8|C8|C8|C8|C8|FF|FF|FF|FF|
|C8|C8|C8|C8|FF|FF|FF|FF|FF|FF|FF|FF|C8|C8|C8|C8|
|C8|C8|C8|C8|C8|C8|C8|C8|FF|FF|FF|FF|FF|FF|FF|FF|
|2°°°°°°°"V°°'W°°
}}
{{HexRow|0x20|
|'''''00'''''|'''''04'''''|'''''04'''''|'''''00'''''|'''''20'''''|'''''00'''''|'''''F4'''''|'''''03'''''
|'''''07'''''|'''''00'''''|'''''00'''''|'''''01'''''|'''''00'''''|'''''00'''''|'''''00'''''|'''''02'''''|
|FF|FF|00|00|C8|C8|B0|B0|E7|E7|FF|FF|FF|FF|FF|FF|
|C8|C8|FF|FF|7C|7C|C3|C3|CE|CE|DD|DD|DD|DD|DD|DD|
|00|00|C8|C8|64|64|D4|D4|A5|A5|DD|DD|DD|DD|DD|DD|
|°°°° °ô°°°°°°°°
}}
{{HexRow|0x30|
|'''''00'''''|'''''FF'''''|'''''00'''''|'''''00'''''|'''''00'''''|'''''00'''''|'''''C0'''''|'''''00'''''
|'''''40'''''|'''''00'''''|'''''F0'''''|'''''00'''''|'''''00'''''|'''''00'''''|'''''CC'''''|'''''01'''''|
|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|
|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|
|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|DD|
|°ÿ°°°°À°@°ð°°°Ì°
}}
{{HexRow|0x40|
|'''''30'''''|'''''FF'''''|'''''88'''''|'''''01'''''|'''''18'''''|'''''FF'''''|66|61|63|74|04|00|00|00|8A|05|
|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|C8|C8|C8|C8|C8|C8|
|DD|DD|DD|DD|DD|DD|00|00|00|00|FF|FF|FF|FF|00|00|
|DD|DD|DD|DD|DD|DD|C8|C8|C8|C8|00|00|00|00|FF|FF|
|0ÿˆ°°ÿfact°°°°Š°
}}
{{HexRow|0x50|
|01|00|64|61|74|61|00|0C|01|00|05|05|10|00|10|00|
|C8|C8|C8|C8|C8|C8|00|00|00|00|FF|FF|FF|FF|FF|FF|
|00|00|C8|C8|C8|C8|FF|FF|FF|FF|00|00|00|00|00|00|
|FF|FF|FF|FF|FF|FF|C8|C8|C8|C8|FF|FF|FF|FF|FF|FF|
|°°data°°°°°°°°°°
}}
{{HexRow|0x60|
|0C|00|AF|FF|2E|00|B4|FF|F0|F1|00|00|0F|30|20|10|
|FF|FF|FF|FF|FF|FF|FF|FF|00|00|00|00|00|00|00|00|
|00|00|00|00|00|00|00|00|C8|C8|C8|C8|C8|C8|C8|C8|
|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|
|°°¯ÿ.°´ÿðñ°°°0°°
}}
|}
:(The contents of the "fmt " header, relevant to SNDD storage, has been highlighted in '''''bold italic'''''.)
{{Table}}
{{OBDth}}
{{OBDtr| 0x00 | char[4]  |FF0000| 52 49 46 46 | RIFF      | identifier for the "IBM/Microsoft RIFF" standard }}
{{OBDtr| 0x04 | uint32  |FFFF00| 4E 0C 01 00 | 68686    | size of the RIFF container from 0x08 to end of file }}
{{OBDtr| 0x08 | char[4]  |00FF00| 57 41 56 45 | WAVE      | identifier for the "WAVE" format }}
{{OBDtr| 0x0C | char[4]  |00FFFF| 66 6D 74 20 | "fmt "    | identifier announcing the following "fmt " (format) section }}
{{OBDtr| 0x10 | uint32  |FFC8C8| 32 00 00 00 | 50        | content size for the "fmt " section, in bytes (typically 50 for MS ADPCM) }}
{{OBDtr| 0x14 | uint16  |FFFFC8| '''''02 00'''''      | 2        | format ID (2 <nowiki>=</nowiki> MS ADPCM format) }}
{{OBDtr| 0x16 | uint16  |C8FFC8| '''''02 00'''''      | 2        | number of channels (2 <nowiki>=</nowiki> stereo) }}
{{OBDtr| 0x18 | uint32  |C8FFFF| '''''22 56 00 00''''' | 22050    | sample rate in Hz (samples per second), a.k.a. "sampling frequency" }}
{{OBDtr| 0x1C | uint32  |FFC8FF| '''''27 57 00 00''''' | 22311    | [[image:sndd_hd1.gif]]
:<small>'''N.B.''' The data rate (in bytes per second) is truncated to the lower integer value.</small> }}
{{OBDtr| 0x20 | uint16  |FFC800| '''''00 04'''''      | 1024      | block alignment a.k.a "block size", in bytes
:<small>'''N.B.''' The block size for MS ADPCM is typically a power of two.</small> }}
{{OBDtr| 0x22 | uint16  |00FFC8| '''''04 00'''''      | 4        | bits per sample (per channel); typically 4 bits for MS ADPCM }}
{{OBDtr| 0x24 | uint16  |C87C64| '''''20 00'''''      | 32        | size of the following extended format specification, in bytes }}
{{OBDtr| 0x26 | uint16  |B0C3D4| '''''F4 03'''''      | 1012      | [[image:sndd_hd2.gif]] }}
{{OBDtr| 0x28 | uint16  |E7CEA5| '''''07 00'''''      | 7        | number of the following coefficient pairs; always 7 in practice }}
|-align=center valign=top
| 0x2A || int16-16 || bgcolor="#FFDDDD" | '''''00 01 00 00''''' || 256, 0 || rowspan=7 align=left | The coefficient pairs themselves (always the same in practice).<br>[[image:sndd_hd3.gif]]
|-align=center valign=top
| 0x2E || int16-16 || bgcolor="#FFDDDD" | '''''00 02 00 FF''''' || 512, -256
|-align=center valign=top
| 0x32 || int16-16 || bgcolor="#FFDDDD" | '''''00 00 00 00''''' || 0, 0
|-align=center valign=top
| 0x36 || int16-16 || bgcolor="#FFDDDD" | '''''C0 00 40 00''''' || 192, 64
|-align=center valign=top
| 0x3A || int16-16 || bgcolor="#FFDDDD" | '''''F0 00 00 00''''' || 240, 0
|-align=center valign=top
| 0x3E || int16-16 || bgcolor="#FFDDDD" | '''''CC 01 30 FF''''' || 460, -208
|-align=center valign=top
| 0x42 || int16-16 || bgcolor="#FFDDDD" | '''''88 01 18 FF''''' || 392, -232
{{OBDtr| 0x46 | char[4]  |FF00C8| 66 61 63 74 | fact      | identifier announcing the following "fact" section }}
{{OBDtr| 0x4A | int32    |C8FF00| 04 00 00 00 | 4        | size of the following "fact" section in bytes }}
{{OBDtr| 0x4E | int32    |C800FF| 8A 05 01 00 | 66954    | actual number of samples (see below for calculation) }}
{{OBDtr| 0x52 | char[4]  |C8C8FF| 64 61 74 61 | data      | identifier announcing the following "data" section }}
{{OBDtr| 0x56 | int32    |00FFC8| 00 0C 01 00 | 68608    | size of the following "data" section in bytes (67 blocks of 1024 bytes) }}
{{OBDtr| 0x5A | block[14]|FF00FF| 05 05 10 00 10 00 0C<br>00 AF FF 2E 00 B4 FF | (5,5) (16,16)<br>(12,-81) (46,-76)| the header of the first 1024-byte block (14 bytes for a stereo block) }}
{{OBDtr| 0x68 | byte[8]...|00C8FF| F0 F1 00 00<br>00 30 20 10 | (-1,0) (-1,1) (0,0) (0,0)<br>(0,0) (3,0) (2,0) (1,0)| the first 8 pairs of nibbles (stereo samples); 1002 more bytes follow }}
|}
-->


[[image:sndd_all.gif]]
[[image:sndd_all.gif]]


{{Table}}
{{Table}}
{{OBDth}}
{{OBDth}}
{{OBDtr| 0x00 | res_id  |FF0000| 01 D7 08 00 | 2263      | 02263-comguy_dth2.aif.SNDD }}
{{OBDtr| 0x00 | res_id  |FF0000| 01 D7 08 00 | 2263      | SNDDcomguy_dth2.aif, instance number #02263 }}
{{OBDtr| 0x04 | lev_id  |FFFF00| 01 00 00 06 | 3        | level 3 }}
{{OBDtr| 0x04 | lev_id  |FFFF00| 01 00 00 06 | 3        | level 3 }}
{{OBDtr| 0x08 | int32    |FFC8C8| 08 00 00 00 | 8        | flags
{{OBDtr| 0x08 | uint32  |FFC8C8| 08 00 00 00 | 8        | flags
:1 - (never used in Vanilla Oni)
:1 - never used in Vanilla Oni; unknown (no effect?)
:2 - (never used in Vanilla Oni)
:2 - never used in Vanilla Oni; unknown (no effect?)
:4 - (never used in Vanilla Oni)
:4 - never used in Vanilla Oni; enables rudimentary format header and IMA4 decoding (overrules "8")
:8 - ADPCM compressed }}
:8 - always used in Vanilla Oni; enables fully-featured format header and PCM / MS ADPCM decoding }}
{{OBDtr| 0x0C | block[50]|FFC8C8| &nbsp;      | &nbsp;    | [[OBD:SNDD/wav|wav header]] (corresponds to the "fmt " section of a RIFF WAVE file)}}
{{OBDtr| 0x0C | block[50]|FFC8C8| &nbsp;      | &nbsp;    | format header (MS ADPCM variant here; can also be IMA4, see below)}}
{{OBDtr| 0x3E | int16    |FFFFC8| 37 00      | 55        | duration in 1/60 seconds (game ticks) }}
{{OBDtr| 0x3E | uint16  |FFFFC8| 37 00      | 55        | duration in 1/60 seconds (game ticks), rounded to the lower value }}
{{OBDtr| 0x40 | int32    |C8FFC8| 56 28 00 00 | 10326    | size of the part in the raw file in bytes }}
{{OBDtr| 0x40 | uint32  |C8FFC8| 56 28 00 00 | 10326    | size of the part in the raw file in bytes }}
{{OBDtr| 0x44 | offset  |C8FFFF| 20 10 59 00 | 0x591020  | at this position starts the part in the raw file }}
{{OBDtr| 0x44 | offset  |C8FFFF| 20 10 59 00 | 0x591020  | at this position starts the part in the raw file }}
{{OBDtr| 0x48 | char[24] |FFC8FF| AD DE      | dead      | 24 unused bytes (padding) }}
{{OBDtr| 0x48 | char[24] |FFC8FF| AD DE      | dead      | 24 unused bytes (padding) }}
|}
|}
;Padding
:The 24 bytes at the end are ''not'' part of the SNDD template. They are not loaded by the Oni engine.
;Duration
:Same as for PC demo and Mac, the duration (number of game ticks) is rounded to the ''lower'' value (a.k.a. "floor") in Vanilla Oni data.<ref name="ticks"/> In other words, it indicates the number of ''complete'' game ticks spanned by the sound's playback.
;Compression modes (flags)
:Unlike for PC demo, there is no single compressed/uncompressed flag in PC retail SNDDs, and no stereo/mono flag either.
:The '''channel count''' is specified in the 50-byte header if said header is enabled, otherwise it is inferred from [[OBD:OSBD/OSGr|OSGr]].
:As for '''compression''', PC retail actually has ''three'' primary compression modes, commanded by the flag values. Only the first is used in Vanilla Oni.
===WAVE-like format header ("8" flag)===
If the "8" flag of the SNDD (at 0x08) is ON and the "4" flag is OFF (as is always the case in Vanilla Oni), the 50-byte block is interpreted as a standard "fmt " chunk that you find in WAVE files (see [[/wav|HERE]] for details).


The .raw data contains the actual audio sample blocks without any other headers (other than ADPCM block headers).
[[image:sndd_hd.gif]]
 
{{Table}}
{{OBDth}}
{{OBDtr| 0x0C | int16    |FFFFC8| 01 00      | 2    | format ID (2 <nowiki>=</nowiki> MS ADPCM format)
:<small>'''N.B.''' At the time of writing, only "1" (linear PCM) and "2" (MS ADPCM) are known to work in Oni; in Vanilla Oni, only MS ADPCM is ever used.</small>}}
{{OBDtr| 0x0E | int16    |C8FFC8| 01 00      | 1    | number of channels (1 <nowiki>=</nowiki> mono)
:<small>'''N.B.''' Both PCM and ADPCM support only mono and stereo sounds, i.e., 1 or 2 channels.</small>}}
{{OBDtr| 0x10 | int32    |C8FFFF| 22 56 00 00 | 22050 | sample rate in Hz (samples per second), a.k.a. "sampling frequency" }}
{{OBDtr| 0x14 | int32    |FFC8FF| 93 2B 00 00 | 11155 | [[image:sndd_hd1.gif]]
:<small>'''N.B.''' For PCM, the data rate is simply "samples per second"*"block alignment", seeing as each sample gets its own block.</small>
:<small>'''N.B.''' For ADPCM, the average data rate is based on whole ADPCM blocks (not accounting for how Oni truncates the .raw data).</small>}}
{{OBDtr| 0x18 | int16    |FFC800| 02 00      | 512  | block alignment a.k.a "block size", in bytes
:<small>'''N.B.''' The block size is trivially 2 bytes for PCM mono (one 16-bit sample) and 4 bytes for PCM stereo (Left and Right 16-bit samples).</small>
:<small>'''N.B.''' For ADPCM, Oni's Vanilla data always uses 512 bytes per channel for 22050 Hz waveforms, and 1024 bytes for 44.1 kHz mono (see below).}}
{{OBDtr| 0x1A | int16    |C800C8| 10 00      | 16    | bits per sample (per channel); typically 16 bits for PCM
{{OBDtrBK|1=Special extended ADPCM wav format header (black outline); fully ignored if the format ID is 1 }}
{{OBDtr| 0x1C | int16    |C87C64| 20 00      | 32    | size of the extra ADPCM parameters, in bytes; typically always 32 }}
{{OBDtr| 0x1E | int16    |B0C3D4| F4 03      | 1012  | [[image:sndd_hd2.gif]] }}
{{OBDtr| 0x20 | int16    |E7CEA5| 07 00      | 7    | number of the following coefficient pairs; always 7 in practice }}
|-align=center valign=top
| 0x22 || int16-16 || bgcolor="#FFDDDD" | 00 01 00 00 || 256, 0 || rowspan=7 align=left | The coefficient pairs themselves (always the same in practice).<br>[[image:sndd_hd3.gif|left]]
|-align=center valign=top
| 0x26 || int16-16 || bgcolor="#FFDDDD" | 00 02 00 FF || 512, -256
|-align=center valign=top
| 0x2A || int16-16 || bgcolor="#FFDDDD" | 00 00 00 00 || 0, 0
|-align=center valign=top
| 0x2E || int16-16 || bgcolor="#FFDDDD" | C0 00 40 00 || 192, 64
|-align=center valign=top
| 0x32 || int16-16 || bgcolor="#FFDDDD" | F0 00 00 00 || 240, 0
|-align=center valign=top
| 0x36 || int16-16 || bgcolor="#FFDDDD" | CC 01 30 FF || 460, -208
|-align=center valign=top
| 0x3A || int16-16 || bgcolor="#FFDDDD" | 88 01 18 FF || 392, -232
|}
;PCM vs ADPCM
:Although Vanilla Oni SNDDs only ever use MS ADPCM waveforms, some mods have successfully used the (bloated!!!) PCM format.
:For PCM, the format ID (at 0x0C) is set to 1, the block size and data rate are simplified, and everything between 0x1C 0x3E is ignored. 
:See [[/wav#PCM_.28with_.22fmt_.22.29|HERE]] for more details on the importing procedure, but keep in mind that PCM waveforms are ''not'' recommended!
;ADPCM coefficients
:The 14 coefficients are de-facto standard, but custom values are formally allowed by the MS ADPCM algorithm.
:Therefore, each MS ADPCM waveform is always accompanied by the coefficient pairs that were used to encode it.
:Thus, even though these numbers are practically always the same, they are required; don't ever mess with them.
;Standard sets of ADPCM parameters
Below are the three types of headers occurring for Vanilla Oni's sounds (MS ADPCM).
----
22.05 kHz mono (used for the vast majority of sounds):
:'''1''' channel; sample rate '''''22050''''' Hz; average data rate '''11155''' B/s (truncated from ~11155.7312253 = 22050*512/1012);
:block alignment '''''512''''' bytes; '''4''' bits per sample; '''''1012''''' samples per block (= 2 + (512 - 7)*8/4/1); standard coefficient table.
{|cellpadding=3 cellspacing=0 style="line-height:13px"
{{HexRow|0x00|
|°°|°°|°°|°°|°°|°°|°°|°°|08|00|00|00|02|00|'''01'''|'''00'''|
}}
{{HexRow|0x10|
|'''''22'''''|'''''56'''''|'''''00'''''|'''''00'''''
|'''93'''|'''2B'''|'''00'''|'''00'''
|'''''00'''''|'''''02'''''
|'''04'''|'''00'''
|20|00
|'''''F4'''''|'''''03'''''
}}
{{HexRow|0x20|
|07|00|00|01|00|00|00|02|00|FF|00|00|00|00|C0|00|
}}
{{HexRow|0x30|
|40|00|F0|00|00|00|CC|01|30|FF|88|01|18|FF|°°|°°|
}}
|}
----
22.05 kHz stereo (used for music and some ambients):
:'''2''' channels; sample rate '''''22050''''' Hz; average data rate '''22311''' B/s (truncated from ~22311.4624506 = 22050*1024/1012);
:block alignment '''''1024''''' bytes; '''4''' bits per sample; '''''1012''''' samples per block (= 2 + (1024 - 2*7)*8/4/2); standard coefficient table.
{|cellpadding=3 cellspacing=0 style="line-height:13px"
{{HexRow|0x00|
|°°|°°|°°|°°|°°|°°|°°|°°|08|00|00|00|02|00|'''02'''|'''00'''|
}}
{{HexRow|0x10|
|'''''22'''''|'''''56'''''|'''''00'''''|'''''00'''''
|'''27'''|'''57'''|'''00'''|'''00'''
|'''''00'''''|'''''04'''''
|'''04'''|'''00'''
|20|00
|'''''F4'''''|'''''03'''''
}}
{{HexRow|0x20|
|07|00|00|01|00|00|00|02|00|FF|00|00|00|00|C0|00|
}}
{{HexRow|0x30|
|40|00|F0|00|00|00|CC|01|30|FF|88|01|18|FF|°°|°°
}}
|}
----
44 kHz mono (used for '''ap_hit_shld''' and the 45 '''zap##''' sounds):
:'''1''' channel; sample rate '''''44100''''' kHz; average data rate '''22179''' B/s (truncated from ~22179.9607073 = 44100*1024/2036);
:block alignment '''''1024''''' bytes; '''4''' bits per sample; '''''2036''''' samples per block (= 2 + (1024 - 7)*8/4/1); standard coefficient table.
{|cellpadding=3 cellspacing=0 style="line-height:13px"
{{HexRow|0x00|
|°°|°°|°°|°°|°°|°°|°°|°°|08|00|00|00|02|00|'''01'''|'''00'''|
}}
{{HexRow|0x10|
|'''''44'''''|'''''AC'''''|'''''00'''''|'''''00'''''
|'''A3'''|'''56'''|'''00'''|'''00'''
|'''''00'''''|'''''04'''''
|'''04'''|'''00'''
|20|00
|'''''F4'''''|'''''07'''''
}}
{{HexRow|0x20|
|07|00|00|01|00|00|00|02|00|FF|00|00|00|00|C0|00|
}}
{{HexRow|0x30|
|40|00|F0|00|00|00|CC|01|30|FF|88|01|18|FF|°°|°°|
}}
|}
----
Only the 22.05 kHz sounds (mono and stereo) are played back correctly by the PC retail engine. The forty-six 44.1 kHz sounds are interpreted as 22.05 kHz waveforms, and therefore are played back two times slower/lower than intended.
 
For any other combinations of PCM or ADPCM parameters, please refer to the importing routine, [[/wav#MS_ADPCM_2|HERE]].
 
===IMA ADPCM decoding ("4" flag)===
If the "4" flag of the SNDD (at 0x08) is ON, then (regardless of the "4" flag), the .raw data will be interpreted as IMA ADPCM blocks, and the 50-byte format block will be mostly ignored, as well as the ".raw data size" field at 0x40.
 
Here is what the .dat part of the above '''SNDDcomguy_dth2''' would have looked like in IMA4 mode:
{|cellpadding=3 cellspacing=0 style="line-height:13px"
{{HexRow|0x00|
|01|D7|08|00|01|00|00|06|04|00|00|00|00|00|01|00|
|FF|FF|FF|FF|FF|FF|FF|FF|00|00|00|00|80|80|00|00|
|00|00|00|00|FF|FF|FF|FF|FF|FF|FF|FF|80|80|FF|FF|
|00|00|00|00|00|00|00|00|00|00|00|00|80|80|FF|FF|
|°×°°°°°°°°°°°°°
}}
{{HexRow|0x10|
|00|00|00|00|00|00|00|00|52|01|00|00|00|00|00|00|
|80|80|80|80|80|80|80|80|FF|FF|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|00|00|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|FF|FF|80|80|80|80|80|80|
|°°°°°°°°4°°°°°°°
}}
{{HexRow|0x20|
|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|°°°°°°°°°°°°°°°°
}}
{{HexRow|0x30|
|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|°°°°°°°°°°°°°°°°
}}
{{HexRow|0x40|
|00|00|00|00|20|10|59|00|AD|DE|AD|DE|AD|DE|AD|DE|
|80|80|80|80|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|
|80|80|80|80|DD|DD|DD|DD|C8|C8|C8|C8|C8|C8|C8|C8|
|80|80|80|80|DD|DD|DD|DD|FF|FF|FF|FF|FF|FF|FF|FF|
|°°°° °Y°°°°°°°°°
}}
{{HexRow|0x50|
|AD|DE|AD|DE|AD|DE|AD|DE|AD|DE|AD|DE|AD|DE|AD|DE|
|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|
|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|
|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|
|°°°°°°°°°°°°°°°°
}}
|}
:The channel count field in the 50-byte "format" block (at 0x0C) is used in the same way as for a WAVE-like header.
:The "block alignment" field (at 0x18) is used (somewhat counterintuitively) to store the number of IMA4 "packets":
:*for a mono IMA4 sound, packets are 34-byte blocks carrying 64 mono samples each (two bytes of header data and 64 "nibbles", or half-bytes);
:*for a stereo IMA4 sound, packets are ''pairs'' of consecutive 34-byte blocks (the 64 Left samples are stored first, then the 64 Right samples).
:(The actual duration of SNDDcomguy_dth2 is, which at 22.05 kHz requires 338 64-sample blocks, hence the value 0x152 appearing at 0x18.)
:Everything else in the 50-byte format block is ignored, as well as the ".raw data size" usually found at 0x40 (Oni uses the number of packets instead).
 
===Raw PCM (no flags)===
If neither the "4" nor the "8" flags are set (at 0x08 in the .dat part of the SNDD), then the .raw data is apparently copied as-is into the playback buffer.
 
In this "raw" playback mode, the sound will not be reproduced correctly unless it's linear PCM (Little Endian) with 16-bit sample depth, 22.05 kHz sampling rate, and a channel count consistent with the SNDD's [[OBD:OSBD/OSGr|OSGr]] (i.e., the metadata used by Oni's engine to set up the sound's playback).
 
Here is what the .dat part of the above '''SNDDcomguy_dth2''' would have looked like in raw PCM mode:
{|cellpadding=3 cellspacing=0 style="line-height:13px"
{{HexRow|0x00|
|01|D7|08|00|01|00|00|06|00|00|00|00|00|00|00|00|
|FF|FF|FF|FF|FF|FF|FF|FF|00|00|00|00|80|80|80|80|
|00|00|00|00|FF|FF|FF|FF|FF|FF|FF|FF|80|80|80|80|
|00|00|00|00|00|00|00|00|00|00|00|00|80|80|80|80|
|°×°°°°°°°°°°°°°
}}
{{HexRow|0x10|
|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|°°°°°°°°°°°°°°°°
}}
{{HexRow|0x20|
|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|°°°°°°°°°°°°°°°°
}}
{{HexRow|0x30|
|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|80|
|°°°°°°°°°°°°°°°°
}}
{{HexRow|0x40|
|00|00|00|00|20|10|59|00|AD|DE|AD|DE|AD|DE|AD|DE|
|80|80|80|80|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|
|80|80|80|80|DD|DD|DD|DD|C8|C8|C8|C8|C8|C8|C8|C8|
|80|80|80|80|DD|DD|DD|DD|FF|FF|FF|FF|FF|FF|FF|FF|
|°°°° °Y°°°°°°°°°
}}
{{HexRow|0x50|
|AD|DE|AD|DE|AD|DE|AD|DE|AD|DE|AD|DE|AD|DE|AD|DE|
|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|
|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|C8|
|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|FF|
|°°°°°°°°°°°°°°°°
}}
|}
;Effect of "1" and "2" flags
:It is possible that the "1" and "2" flags used to affect playback in raw PCM mode (something about swapping the .raw data to allow both for Little Endian and Big Endian PCM samples), but currently the do not seem to have any effect.
 
<!--
The '''duration''' (number of game ticks) is rounded to the ''lower'' value (a.k.a. "floor") in Vanilla Oni data. For example, on PC, '''SNDDmus_ot7.aif''' consists of 152360 samples, which at 22.05 kHz corresponds to 6.90975 seconds, or 414.585 ticks; the duration, however, is indicated as 414 ticks and not 415.
;Flags 0x00000001 and 0x00000002
:Setting these two flags in a PC retail SNDD file has no noticeable effect, both on their own and in combination with the other two. Possibly they are for runtime use.
;Behavior without 0x00000004 or 0x00000008
:If neither the 0x00000004 nor the 0x00000008 flags are set, the stream data from .raw is apparently copied as-is to the output buffer. The expected sample rate is 22.05 kHz, the expected sample type is regular PCM (Little-Endian signed 16-bit linear), and the channel count of the buffer is determined at OSGr level. Note that 22.05 kHz PCM data can also be supplied more explicitly, with the 0x00000008 flag enabled, and PCM parameters listed in the WAVEfmt header: sample rate (ignored), channel count and bit depth.
;Behavior with 0x00000004
:If the 0x00000004 flag is set, it overrides 0x00000008 and forces the interpretation of the stream data as IMA4 ADPCM. In this configuration, only two fields of the 50-byte "format" chunk are used: the channel count (at 0xE), and the
;Behavior with 0x00000008 and without 0x00000004
 
===raw PCM data (no 0x4 or 0x8 flag)===
===IMA4 ADPCM data (0x4 flag)===
===WAVEfmt header (0x8 flag and no 0x04)===
-->
==Exporting and importing tips==
*For manual converting between SNDD (PC retail or demo) and a WAVE file, see [[/wav|HERE]].
*For manual converting between SNDD (PC retail or Mac) and an AIFC file, see [[/aif|HERE]].
For automatic conversion, please use a sufficiently recent version of [[OniSplit]].
 
==Known engine issues==
;Custom sample/data rates
:The PC retail engine formally allows for an arbitrary sample rate (and a corresponding data rate) to be specified in the WAVfmt header, but actually the engine interprets all waveforms as 22.05 kHz.
:*If the WAVEfmt header is enabled and specifies MS ADPCM encoding (format ID 2), then the sample rate and data rate are completely ignored (you can fill those fields with zeroes or garbage, and it will still work).
:*If the WAVEfmt header is enabled and specifies PCM storage (format ID 1), then fully arbitrary (inconsistent) sample rate and data rate will cause playback glitches or interruption, whereas mutually consistent pairs ("data rate" equal to "sample rate"x"block size") are eventuall ignored. In other words, you have to specify a valid sample rate and data rate, but the engine will end up using 22.05 kHz anyway.
:*If the IMA4 header is enabled (overriding WAVEfmt), then the header only specifies the channel count and the "number of packets", and the sample/data rates are again completely ignored.
 
;PCM playback
:PCM playback is only known to work in PC retail builds, either with IMA4 and WAVEfmt headers disabled (the stream is simply copied to the output buffer, as Little-Endian 16-bit linear PCM, with the channel count specified at OSGr level) or with the WAVEfmt header enabled (in which case the stream can have a custom bit depth and channel count).
:In the case of PC demo, the PCM playback fails (the engine identifies the stream as already uncompressed and skips the initialization of ACM headers, but then proceeds with decompression anyway and stops because of zero input size). This causes no problems for impulse sounds (other than silence), but results in a crash for looping permutations (the same playback keeps failing over and over).
:On the Mac, the stream is interpreted as IMA4 regardless of the 0x00000001 flag, therefore if you put PCM data in the .raw, it will play back as noise.
==Known data issues==
;PC SNDD data
:The MS ADPCM data used by Vanilla Oni on Windows (both retail and demo) is somewhat coarser (lossier) than the IMA4 ADPCM used on Mac. This is because of the much larger block size, and how the same predictor must be used for the whole block: whenever a block spans both high- and low-amplitude samples, the predictor adapts to the higher amplitudes, and the low-amplitude resolution is lost.
:As a minor issue, the lack of an exact sample count (similar to a WAVE's "fact") makes it impossible to specify an odd number of samples for a mono block (because there is no way to tell if the last byte's second nibble counts or not). It is also impossible to have only one sample in the last block, be it for mono stereo (because the block header reads as two samples by default).
 
;Mac SNDD data
:Unlike Oni's implementation of MS ADPCM, which cuts off the last block after the last actual sample, IMA4 data consists of full 64-sample blocks, with no way to determine the actual sample count other than by comparing with the same sound from PC Oni. (The "padding" of IMA4 sounds is not always zero, and even if it was, truncation based on trailing zeroes would be somewhat arbitrary.) The padding of IMA4 samples to multiples of 64 leads to silences at the end of Mac sounds that can be up to 3 milliseconds long. This is not a problem for impulse sounds or looping sounds that are quiet near the end, but for loud music (e.g. the main menu's "Trailer" theme) the gap is noticeable. It has been confirmed that the gap is actually heard in Mac Oni, apparently without bothering anyone.
:As a hypothetical fix, the Oni engine could implement a sample count parameter (similar to a WAVE file's "fact"), or truncate the last 64-sample block after the last actual sample, upon encoding (the latter is slightly less straightforward for stereo – because there are ''two'' last blocks, one for each channel – but still not a big problem).
:Mac sound data also seems to suffer from encoding artifacts: there are spurious transients at the start of waveforms that prevent ambients and music from looping seamlessly even when cut at the right length. Unlike the padding, this cannot be remedied at all, therefore if one wishes to produce seamless tracks from Oni data (e.g. music) it is recommended to turn to PC SNDDs, which have no looping issues (but are slightly lossier because of the larger block size, as mentioned above).
 
==Modern support==
===OniSplit===
Newer releases (OniSplit v0.9.99.3 and newer) include an implementation of the MS ADPCM and IMA4 codecs, along with the ability to generate .dat/.raw./sep game data compatible with the PC-demo based OniX engine. The codecs allow OniSplit to transcode from Mac's IMA4 or from 44.1 kHz MS ADPCM to standard 22.05 kHz MS ADPCM. PCM is also supported both ways (both as .wav output coming from IMA4 or MS ADPCM, or as uncompressed SNDD intended for the PC retail or demo engines). Finally, for exotic sample rates, there is an option to store the waveform as-is (without resampling) and merely report the appropriate rate multiplier that can be used in OSGr to adjust the speed/pitch upon playback.
 
Older releases (OniSplit v0.9.99.2 and older) did not support ADPCM encoding or decoding, so there was no way to transcode between IMA4, MS ADPCM and PCM. Generating instance files for the demo engine was not supported either.
 
The hybrid SNDD format (aligned with OniX's planned features) has not been implemented in OniSplit yet. The recently discovered PC retail engine features (IMA4 support, or default PCM support) are also not covered by OniSplit at the time of writing.
 
===OniX===
Starting with v1.1, OniX will likely support all three standard streams (IMA4, MS ADPCM and PCM) with their default encoding/storage settings:
*for IMA4, 32-byte blocks with 64 samples per block (interleaved Left-channel and Right-channel blocks if stereo), sample rate 22.05 kHz;
*for MS ADPCM, 512-byte blocks for mono, 1024-byte blocks for stereo, 1012 samples per block in both cases, sample rate 22.05 kHz;
*for PCM, signed linear 16-bit samples, Little Endian storage, sample rate 22.05 kHz.
The engine will determine between the three types of streams using flags in the short SNDD header. Possibly another flag will allow for doubled sample rate (44.1 kHz); in this configuration the default block size will probably be 1024 bytes for mono and 2048 bytes for stereo, with 2036 samples per block in each case.
 
Finally, even with a short SNDD header, it is possible for OniX to read a custom WAVEfmt chunk just like the PC retail engine does, by putting the chunk at the start of the .raw part and announcing its presence and/or size through another flag and/or the unused uint at 0x0E. The typical size of this ".raw header" will be 16 bytes for PCM and 50 bytes for ADPCM (the use of other WAVE formats will probably be discouraged).
 
Alternatively, both the flags and the uint at 0x0E can be used to specify a custom sample rate and/or block size (either as fully custom values or as power-of-two multiplicative factors), without the need for a detailed WAVEfmt header. Still, it is probably easiest to either adhere to the standard parameters (without too many extra flags) or go fully custom and read all the parameters from a standard-compliant WAVEfmt header.
 
<!--
correspond to SScSoundDataFlag_PCM_Big and SScSoundDataFlag_PCM_Little. (traces of flag values found in)
;WAVEfmt/Ext header
:If the 0x00000008 flag is OFF (never used in Oni), the WAVEfmt block is completely ignored, and the engine to "format ID" field in the [[OBD:SNDD/wav|wav header]], and the precedence is as follows:
:*the format ID of the wav header is is always 2 (ADPCM), but many mods use 1 (PCM) instead.
;Padding
:The 24 bytes at the end are ''not'' part of the SNDD template. They are not loaded by the Oni engine.
 
The .raw data contains the actual audio sample blocks without any other headers (other than ADPCM block headers).==
 
 
and 2034 more samples in the case of 44.1 kHz mono)
and 44.1 kHz mono
 
and 2036 for 44.1 kHz mono.
 
:If the "compressed" flag (0x00000001) is enabled, the .raw audio data is assumed to be compressed with MS ADPCM, at 22.05 kHz and with a block size of 512 bytes per channel (on the Mac, IMA4 compression is used, with 34-byte blocks).
:If the "compressed" flag (0x00000001) is disabled, it would be sensible for the engine to assume standard uncompressed PCM (linear signed 16-bit), sampled at 22.05 kHz and just copy that data to the output buffer. Instead the engine merely skips the initialization of the decompression routine, but still attempts to decompress later on, finding no bytes to decode and immediately interrupting playback as if it had completed. For impulse sounds, the system merely plays no sound, and no further problems occur. However, if the sound participates in a looping permutation (randomized or not), then the engine will be stuck in endless recursion within a single tick, chaining up immediately-interrupted playbacks of the same permutation, which ends in a "Blam". The fix is either that Oni should compress any uncompressed SNDDs at runtime (and then run them through the generic decompression routine), or that the playback of uncompressed sounds should use a separate set of rules.
;IMA4 or MS ADPCM?
:In theory the engine can easily determine between MS ADPCM and IMA4, from several criteria:
:*Coarse criterion: if the raw data size is a multiple of 34 bytes, then the data is very probably in IMA4 format (although coincidence can not be ruled out completely);
:*Fine criterion: if ''every'' 34-byte block starts with a valid predictor-step pair, with the 7-bit step value falling in the 0-88 range, this makes IMA4 practically certain.
:*For sufficiently long sounds (starting at ~21 ticks or 0.35 seconds) the "duration" field can be used to validate IMA4 as well: for N samples, the "duration" being '''floor(N/367.5)''' ticks, the .raw size of a IMA4 sound will be '''34*ceil(N/64)''' bytes per channel, whereas for a standard MS ADPCM sound it will not exceed '''512*ceil(N/1012)''' per channel, i.e., about 5% smaller than for IMA4.
 
 
;Key shortcomings of the PC demo and Mac SNDDs as compared to PC retail SNDDs:
*PC demo and Mac SNDDs have a "short" .dat part that specifies only the frame count (animation length in game ticks) and number of channels (mono or stereo). The waveform data is always assumed to be sampled at 22.05 kHz, and compressed into 4-bit ADPCM (either IMA4, on Mac, or MS ADPCM, on PC). Uncompressed PCM playback is broken for PC demo (and probably for Mac as well).
*PC retail SNDDs contain a WAVE "fmt " (format) chunk that can be used to specify arbitrary compression parameters as well as a custom sample rate. In practice, though, Oni always interprets the waveforms as having a 22.05 kHz sample rate. Thus, although the 46 electric spark sounds '''ap_hit_shld''' and '''zap##''' have 44.1 kHz waveforms in PC retail versions of Oni, the actual rendering of these sounds is 2x slower/lower than intended.
;Key shortcomings of Mac SNDDs as compared to PC SNDDs (both retail and demo):
*At 22.05 kHz, the storage size of Mac SNDDs (IMA4) is about 5% larger than for PC equivalents (MS ADPCM), because of a much smaller block size in the .raw part (the smaller .dat part of Mac SNDDs doesn't help).
*Mac SNDDs have encoding/editing artifacts at the ends of looping segments (music and ambient tracks). PC SNDDs (retail or demo) have no such artifacts and allow nearly seamless playback. See [[OBD:SNDD#Looping_issues|BELOW]] for details.
;Key shortcomings of PC SNDDs (both retail and demo) as compared to Mac SNDDs:
*The large block size of PC SNDDs (1012 samples for 22.05 KHz mono or stereo, and 2036 samples for 44.1 kHz mono) is space efficient, but the tradeoff is a coarser sample resolution whenever a block spans a wide range of amplitudes (this is because of how a MS ADPCM block relies on a single "predictor" that accommodates all the waveform samples within that block).
*Custom sample rates are formally supported through the use of the WAVE "fmt " header, but do not actually work, which is frustrating.


====.raw part (MS ADPCM)====
For a detailed overview of the ADPCM algorithm (if interested), see [https://wiki.multimedia.cx/index.php/Microsoft_ADPCM HERE]. For an actual implementation example, see, e.g., [[wp:FFmpeg|FFmpeg]].
:The MS ADPCM .raw data has 512- or 1024-byte blocks (512 bytes for 22.05 kHz mono, 1024 bytes for 22.05 kHz stereo and 44.1 kHz mono)
:Each block consists of a 7- or 14-byte header (7 bytes for mono, 14 bytes for stereo), which includes the block's first two samples.
:The remaining 505, 1010 or 1017 bytes of each block consist of nibbles (half-bytes), with left-right interleaving in the case of stereo.
::(that's 1010 more samples in the case of 22.05 kHz mono or stereo, and 2034 more samples in the case of 44.1 kHz mono)
:Thus the total number of samples per block (including the two in the header) is 1012 for 22.05 kHz (mono or stereo) and 2036 for 44.1 kHz mono.
:The final block in the file can be incomplete (the decoder can infer this from the block size and raw data size).


----
----
Line 49: Line 555:
The Mac version and the PC demo version use a simpler format, with no support for different sample rates (all sounds are sampled at 22050 Hz).
The Mac version and the PC demo version use a simpler format, with no support for different sample rates (all sounds are sampled at 22050 Hz).


[[image:sndd_alm.gif]]
{{Table}}
{{OBDth}}
{{OBDtr| 0x00 | res_id  |FF0000| 01 D6 08 00 | 2262      | 02262-comguy_dth2.aif.SNDD }}
{{OBDtr| 0x04 | lev_id  |FFFF00| 01 00 00 06 | 3        | level 3 }}
{{OBDtr| 0x08 | int32    |FFC8C8| 01 00 00 00 | 1        | flags
:1 - (unknown; always the same in Vanilla Oni)
:2 - stereo (mono if disabled) }}
{{OBDtr| 0x0C | int32    |FFFFC8| 37 00 00 00 | 55        | duration in 1/60 seconds (game ticks) }}
{{OBDtr| 0x10 | int32    |C8FFC8| 5E 2A 00 00 | 10846    | size of the part in the raw file in bytes }}
{{OBDtr| 0x14 | offset  |C8FFFF| 00 B1 01 00 | 0x1B100  | at this position starts the part in the raw file }}
{{OBDtr| 0x18 | char[8]  |FFC8FF| AD DE      | dead      | 8 unused bytes (padding) }}
|}


The .raw data contains the actual audio sample blocks without any other headers (other than ADPCM block headers).
The .raw data contains the actual audio sample blocks without any other headers (other than ADPCM block headers).
====.raw part (MS ADPCM, PC demo)====
====.raw part (MS ADPCM, PC demo)====
For PC demo the .raw SNDD data is actually the same as for PC retail, but with the same short .dat header as on Mac. The ADPCM block size is 512 bytes for mono, and 1024 for stereo. The sample rate is 22.05 kHz.
For PC demo the .raw SNDD data is actually the same as for PC retail, but with the same short .dat header as on Mac. The ADPCM block size is 512 bytes for mono, and 1024 for stereo. The sample rate is 22.05 kHz.
:(Note, however, that the "electric" SNDDs are sampled at 44.1 kHz in PC retail, with 1024 bytes per block even though it's mono. Therefore, for these sounds, the .raw data ''is'' different on PC retail and PC demo.)
====.raw part (IMA4 ADPCM, Mac)====
====.raw part (IMA4 ADPCM, Mac)====
For an overview of the IMA ADPCM algorithm and IMA4 header (if interested), see [https://wiki.multimedia.cx/index.php/Apple_QuickTime_IMA_ADPCM HERE]
For an overview of the IMA ADPCM algorithm and IMA4 header (if interested), see [https://wiki.multimedia.cx/index.php/Apple_QuickTime_IMA_ADPCM HERE]
:The IMA4 ADPCM data has 34-byte blocks (in the case of stereo, there is an even number of such blocks, because Left and Right blocks are interleaved).
:The IMA4 ADPCM data has 34-byte blocks (in the case of stereo, there is an even number of such blocks, because Left and Right blocks are interleaved).
:The first two bytes of each block are used to set the initial predictor (upper 9 bits) and step (lower 7 bits) for decoding the block's samples.
:The first two bytes of each block is a header that  set the initial predictor (upper 9 bits) and step (lower 7 bits) for decoding the block's samples. Typically they are only used only for the first block
:The other 32 bytes consist of 64 samples stored as nibbles (half-bytes). In the case of stereo, all the nibbles in a block belong to the same channel (either all Left or all Right).
:The other 32 bytes consist of 64 samples stored as nibbles (half-bytes). In the case of stereo, all the nibbles in a block belong to the same channel (either all Left or all Right).
:Unlike for MS ADPCM, incomplete trailing blocks (if any) are not indicated in any way: the final blocks are stored in their entirety, with no way to tell how much of it is actual data.
:Unlike for MS ADPCM, incomplete trailing blocks (if any) are not indicated in any way: the final blocks are stored in their entirety, with no way to tell how much of it is actual data.
Line 124: Line 614:
By looking at the end of the Mac SNDDs (or the exported AIFF files), it can be confirmed that the extraneous samples are actually there, at the end of the last two 34-byte blocks (last Left block and last Right block), with no way to interrupt playback upon reaching these trailing samples - because they are no different from regular samples.
By looking at the end of the Mac SNDDs (or the exported AIFF files), it can be confirmed that the extraneous samples are actually there, at the end of the last two 34-byte blocks (last Left block and last Right block), with no way to interrupt playback upon reaching these trailing samples - because they are no different from regular samples.


Also, from a careful examination of the sound stream that is actually played back by Oni in the main menu, it is clear that all the Oni engines (both Mac and PC) play back all the available data (including the "padding" of the fixed-size IMA4 blocks) before switching to the next segment. The frame count (number of game ticks) is ignored or used only as an indication (e.g., for approximate cueing in [[BSL]]).
Also, from a careful examination of the sound stream that is actually played back by Oni in the main menu, it is clear that all the Oni engines (both Mac and PC) play back all the available data (including the "padding" of the fixed-size IMA4 blocks) before switching to the next segment. The frame count (number of game ticks) does not affect a sound's playback and is used only as an indication for subsequent sounds (e.g., for approximate cueing in [[BSL]]).


This uninterrupted playback of fixed-size IMA4 blocks is one of the aspects that impact seamless playback of sound sequences in Mac Oni (music or ambient tracks). See [[OBD:SNDD#Looping_issues|"Looping Issues"]] below.
This uninterrupted playback of fixed-size IMA4 blocks is one of the aspects that impact seamless playback of sound sequences in Mac Oni (music or ambient tracks). See [[OBD:SNDD#Looping_issues|"Looping Issues"]] below.
Line 185: Line 675:
* n_samples = n_whole_blocks*samples_per_block + last_block_samples;        '''// EXAMPLE: 20*1012 + 160 = 20400'''
* n_samples = n_whole_blocks*samples_per_block + last_block_samples;        '''// EXAMPLE: 20*1012 + 160 = 20400'''


----
===AIF files (from Mac SNDDs)===
*Write "FORM"
*add the size of the part in the raw file + 50 bytes
*write "AIFC"
*write "COMM "
*add the aif header (after filling in in, the number of channels, the sample rate - always 22.05 kHz -, the bits per sample - always 16 - and the number of sample frames/blocks)
*write "SSND"
*add the size of the part in the raw file + 8 bytes
*add 8 zero bytes (custom "offset" and "block size" fields)
*add the raw file data and save it as an aif file.
Note the [[wikipedia:Big Endian|Big Endian]] order
[[image:sndm_aif.gif]]
{{Table}}
{{OBDth}}
{{OBDtrBK|Complete aif format header (black outline) }}
{{OBDtr| 0x00 | char[4]  |FF0000| 46 4F 52 4D | FORM      | identifier for the "EA IFF 85" standard }}
{{OBDtr| 0x04 | int32    |FFFF00| 00 00 2A 90 | 10896    | size of the file from 0x08 to the end (<nowiki>=</nowiki> size of the .raw part + 50 bytes) }}
{{OBDtr| 0x08 | char[4]  |00FF00| 41 49 46 43 | AIFC      | identifier for the "AIFC" format (compressed aif file) }}
{{OBDtr| 0x0C | char[4]  |00FFFF| 43 4F 4D 4D | COMM      | identifier announcing the following aif format header }}
{{OBDtr| 0x10 | block[26]|FFC8C8| &nbsp;      | &nbsp;    | [[OBD:SNDD/aif|aif header]] }}
{{OBDtr| 0x2A | char[4]  |FFFFC8| 53 53 4E 44 | SSND      | identifier announcing the following aif data }}
{{OBDtr| 0x2E | int32    |C8FFC8| 00 00 2A 66 | 10854    | size of the file from 0x32 to the end (<nowiki>=</nowiki> size of the .raw part + 8 bytes) }}
{{OBDtr| 0x32 | int32    |C8FFFF| 00 00 00 00 | 0        | offset; determines where the first sample in the data starts; use zero }}
{{OBDtr| 0x36 | int32    |FFC8FF| 00 00 00 00 | 0        | block size; used in conjunction with offset for block-aligning data; use zero }}
|}




Line 252: Line 714:
Importing SNDDs for PC demo (with a short .dat part and MS ADPCM in the .raw part) is also not implemented yet. Last but not least, PC retail apparently supports uncompressed PCM sounds, but they need to be tested in the engine first. Possibly ADPCM encoding/transcoding will be implemented at some point, too.
Importing SNDDs for PC demo (with a short .dat part and MS ADPCM in the .raw part) is also not implemented yet. Last but not least, PC retail apparently supports uncompressed PCM sounds, but they need to be tested in the engine first. Possibly ADPCM encoding/transcoding will be implemented at some point, too.


-->
==Notes==
<references/>
----
----
{{OBD_File_Footer | type=SNDD | prev=QTNA | next=StNA | name=Sound Data | family=Generic}}
{{OBD_File_Footer | type=SNDD | prev=QTNA | next=StNA | name=Sound Data | family=Generic}}


{{OBD}}
{{OBD}}

Revision as of 12:22, 30 July 2021

ONI BINARY DATA
QTNA << Other file types >> StNA
SNDD : Sound Data
switch to XML:SNDD page
Overview @ Oni Stuff
OBD.png
For metadata instances used to group sounds together, randomize them, adjust their volume or frequency, etc, see OSBD and its subtypes: OSAm, OSIm and OSGr.

SNDD instances is where Oni stores sound data. In Vanilla Oni game data, sounds are either mono or stereo waveforms (with sampling frequencies of either 22.05 kHz or 44.1 kHz), compressed to save on storage space. Both the PC and Mac versions use a form of ADPCM compression (Adaptive Differential Pulse-Code Modulation), where 16-bit sound samples are encoded as 4-bit "nibbles" (resulting roughly in a 4:1 compression ratio as compared to uncompressed 16-bit PCM).

  • On PC (both retail and demo), sounds are encoded using Microsoft's ADPCM codec (implemented in FFmpeg as adpcm_ms). See HERE for a quick description.
  • On Mac, sounds are encoded using QuickTime's IMA4 codec (implemented in FFmpeg as adpcm_ima_qt). See HERE for a quick description.

As a unique feature of Oni game data, SNDD files have a significantly different structure depending on the engine version. For PC retail (.dat/.raw storage, no .sep files), the SNDD files are larger and include a 50-byte chunk of data that is equivalent to the "fmt " chunk of a WAVE file. For the other two versions (PC demo and Mac, .dat/.raw/.sep storage), this 50-byte block is missing. It turns out that the extra format data allows the PC retail to support both MS ADPCM and IMA4, as well as uncompressed PCM, whereas PC demo and Mac engines only support MS ADPCM and IMA4, respectively. (It has not been confirmed whether the PC retail engine supports other WAVE formats beyond PCM and MS ADPCM, such as Mu-Law or A-Law PCM, IEEE float PCM, etc.)

For clarity, the simpler and more straightforward SNDDs of PC demo and Mac are documented first, followed by the more complex and versatile PC retail SNDDs.

(Historically, though, the PC retail implementation is older, and the PC demo and Mac versions were trimmed-down iterations of PC retail.)

Mac and PC demo

The below example was taken from Mac Oni. In PC demo the file would look the same, except for possibly different res_id (at 0x00) and smaller raw data size (at 0x10).

Sndd alm.gif

Offset Type Raw Hex Value Description
0x00 res_id 01 D6 08 00 2262 SNDDcomguy_dth2.aif, instance number #2262
0x04 lev_id 01 00 00 06 3 level 3
0x08 uint32 01 00 00 00 1 flags
1 - (compressed; always the same in Vanilla Oni)
2 - stereo (mono if disabled)
0x0C uint16 37 00 55 duration in 1/60 seconds (game ticks)
0x0E uint16 00 00 0x0000 padding (unused in Vanilla Oni)
0x10 uint32 5E 2A 00 00 10846 size of the part in the raw file, in bytes
0x14 offset 00 B1 01 00 0x1B100 at this position starts the part in the raw file
0x18 char[8] AD DE dead 8 unused bytes (padding; not part of the SNDD file)
Padding
The 8 bytes at the end are not part of the SNDD template. They are not loaded by the Oni engine.
The uint16 at 0x0E is loaded by the engine, and thus constitutes a potentially useful 16-bit field.
Duration
The duration (number of game ticks) is rounded to the lower value (a.k.a. "floor") in Vanilla Oni data.[1] In other words, it indicates the number of complete game ticks spanned by the sound's playback.
Compression
The effect of the "1" flag (or rather of its absence) is different in the PC demo and Mac engines.
  • On Mac, the flag seems to have no effect at all (the .raw data is still passed to the IMA4 decoding algorithm even if the "1" flag is missing).
  • On PC demo, a missing "1" flag causes playback to fail.[2] If the sound is part of a looping permutation, the game crashes (because playback keeps failing on the same sound, over and over).
The bottom line is that, both for PC demo SNDDs and for Mac SNDDs, the "1" flag should always be set.

The compressed storage of .raw data is described in the following two sections.

IMA4 ADPCM .raw data (Mac)

For an overview of the IMA ADPCM algorithm and IMA4 header (if interested), see HERE. For an actual implementation example, see, e.g., FFmpeg.

The IMA4 ADPCM stream data (stored in the .raw file) consists of 34-byte blocks (in the case of stereo, there is an even number of such blocks, with Left and Right blocks interleaved).
The first two bytes of each block form a header that sets the initial predictor (upper 9 bits) and step (lower 7 bits) for decoding the block's samples. Typically they are used only for the first block, or for sudden changes of the waveform's value range.
The other 32 bytes consist of 64 samples stored as nibbles (half-bytes). In the case of stereo, all the nibbles in a block belong to the same channel (either all Left or all Right).
All the 32-byte blocks must be stored in their entirety, meaning that the overall sample count of the waveform is a multiple of 64 (this is a major difference from MS ADPCM storage in PC retail and PC demo, where the final block is truncated after the last actual sample).
For this reason, identical sounds do not have the same sample count on PC (both retail and demo) and on Mac. As an example, here are the stats for the main menu music:

MS ADPCM .raw data (PC demo)

For a detailed overview of the ADPCM algorithm (if interested), see HERE. For an actual implementation example, see, e.g., FFmpeg.

The MS ADPCM stream data (stored in .raw) consists of 512- or 1024-byte blocks (512 bytes for 22.05 kHz mono, 1024 bytes for 22.05 kHz stereo)
Each block starts with a 7- or 14-byte header (7 bytes for mono, 14 bytes for stereo), which includes the 16-bit values of the block's first two samples.
The remaining 505 or 1010 bytes of each block consist of nibbles (half-bytes), each coding for a sample. In the case of stereo, Left and Right nibbles are interleaved.
Thus the block has room for 1010 samples encoded as nibbles, and the total number of samples per block (including the header) is 1012, be it for mono or stereo 22.05 kHz.
For space efficiency, the MS ADPCM stored in .raw deviates from the standard, in that the final block is truncated after the last actual sample. In a WAVE file, ADPCM blocks are stored in their entirety, and the actual sample count is specified in a "fact" chunk. In Oni there is no such thing, instead the actual sample count is inferred from the block size and truncated raw data size.

PC retail

Below is the .dat file part used in the PC retail version.

Sndd all.gif

Offset Type Raw Hex Value Description
0x00 res_id 01 D7 08 00 2263 SNDDcomguy_dth2.aif, instance number #02263
0x04 lev_id 01 00 00 06 3 level 3
0x08 uint32 08 00 00 00 8 flags
1 - never used in Vanilla Oni; unknown (no effect?)
2 - never used in Vanilla Oni; unknown (no effect?)
4 - never used in Vanilla Oni; enables rudimentary format header and IMA4 decoding (overrules "8")
8 - always used in Vanilla Oni; enables fully-featured format header and PCM / MS ADPCM decoding
0x0C block[50]     format header (MS ADPCM variant here; can also be IMA4, see below)
0x3E uint16 37 00 55 duration in 1/60 seconds (game ticks), rounded to the lower value
0x40 uint32 56 28 00 00 10326 size of the part in the raw file in bytes
0x44 offset 20 10 59 00 0x591020 at this position starts the part in the raw file
0x48 char[24] AD DE dead 24 unused bytes (padding)
Padding
The 24 bytes at the end are not part of the SNDD template. They are not loaded by the Oni engine.
Duration
Same as for PC demo and Mac, the duration (number of game ticks) is rounded to the lower value (a.k.a. "floor") in Vanilla Oni data.[1] In other words, it indicates the number of complete game ticks spanned by the sound's playback.
Compression modes (flags)
Unlike for PC demo, there is no single compressed/uncompressed flag in PC retail SNDDs, and no stereo/mono flag either.
The channel count is specified in the 50-byte header if said header is enabled, otherwise it is inferred from OSGr.
As for compression, PC retail actually has three primary compression modes, commanded by the flag values. Only the first is used in Vanilla Oni.

WAVE-like format header ("8" flag)

If the "8" flag of the SNDD (at 0x08) is ON and the "4" flag is OFF (as is always the case in Vanilla Oni), the 50-byte block is interpreted as a standard "fmt " chunk that you find in WAVE files (see HERE for details).

Sndd hd.gif

Offset Type Raw Hex Value Description
0x0C int16 01 00 2 format ID (2 = MS ADPCM format)
N.B. At the time of writing, only "1" (linear PCM) and "2" (MS ADPCM) are known to work in Oni; in Vanilla Oni, only MS ADPCM is ever used.
0x0E int16 01 00 1 number of channels (1 = mono)
N.B. Both PCM and ADPCM support only mono and stereo sounds, i.e., 1 or 2 channels.
0x10 int32 22 56 00 00 22050 sample rate in Hz (samples per second), a.k.a. "sampling frequency"
0x14 int32 93 2B 00 00 11155 File:Sndd hd1.gif
N.B. For PCM, the data rate is simply "samples per second"*"block alignment", seeing as each sample gets its own block.
N.B. For ADPCM, the average data rate is based on whole ADPCM blocks (not accounting for how Oni truncates the .raw data).
0x18 int16 02 00 512 block alignment a.k.a "block size", in bytes
N.B. The block size is trivially 2 bytes for PCM mono (one 16-bit sample) and 4 bytes for PCM stereo (Left and Right 16-bit samples).
N.B. For ADPCM, Oni's Vanilla data always uses 512 bytes per channel for 22050 Hz waveforms, and 1024 bytes for 44.1 kHz mono (see below).

{{OBDtr| 0x1A | int16 |C800C8| 10 00 | 16 | bits per sample (per channel); typically 16 bits for PCM

Special extended ADPCM wav format header (black outline); fully ignored if the format ID is 1
0x1C int16 20 00 32 size of the extra ADPCM parameters, in bytes; typically always 32
0x1E int16 F4 03 1012 File:Sndd hd2.gif
0x20 int16 07 00 7 number of the following coefficient pairs; always 7 in practice
0x22 int16-16 00 01 00 00 256, 0 The coefficient pairs themselves (always the same in practice).
File:Sndd hd3.gif
0x26 int16-16 00 02 00 FF 512, -256
0x2A int16-16 00 00 00 00 0, 0
0x2E int16-16 C0 00 40 00 192, 64
0x32 int16-16 F0 00 00 00 240, 0
0x36 int16-16 CC 01 30 FF 460, -208
0x3A int16-16 88 01 18 FF 392, -232
PCM vs ADPCM
Although Vanilla Oni SNDDs only ever use MS ADPCM waveforms, some mods have successfully used the (bloated!!!) PCM format.
For PCM, the format ID (at 0x0C) is set to 1, the block size and data rate are simplified, and everything between 0x1C 0x3E is ignored.
See HERE for more details on the importing procedure, but keep in mind that PCM waveforms are not recommended!
ADPCM coefficients
The 14 coefficients are de-facto standard, but custom values are formally allowed by the MS ADPCM algorithm.
Therefore, each MS ADPCM waveform is always accompanied by the coefficient pairs that were used to encode it.
Thus, even though these numbers are practically always the same, they are required; don't ever mess with them.
Standard sets of ADPCM parameters

Below are the three types of headers occurring for Vanilla Oni's sounds (MS ADPCM).

22.05 kHz mono (used for the vast majority of sounds):

1 channel; sample rate 22050 Hz; average data rate 11155 B/s (truncated from ~11155.7312253 = 22050*512/1012);
block alignment 512 bytes; 4 bits per sample; 1012 samples per block (= 2 + (512 - 7)*8/4/1); standard coefficient table.
0x00:  °° °° °° °° °° °° °° °° 08 00 00 00 02 00 01 00  °°°°°°°°°°°°°°°°
0x10:  22 56 00 00 93 2B 00 00 00 02 04 00 20 00 F4 03  °°°°°°°°°°°°°°°°
0x20:  07 00 00 01 00 00 00 02 00 FF 00 00 00 00 C0 00  °°°°°°°°°°°°°°°°
0x30:  40 00 F0 00 00 00 CC 01 30 FF 88 01 18 FF °° °°  °°°°°°°°°°°°°°°°

22.05 kHz stereo (used for music and some ambients):

2 channels; sample rate 22050 Hz; average data rate 22311 B/s (truncated from ~22311.4624506 = 22050*1024/1012);
block alignment 1024 bytes; 4 bits per sample; 1012 samples per block (= 2 + (1024 - 2*7)*8/4/2); standard coefficient table.
0x00:  °° °° °° °° °° °° °° °° 08 00 00 00 02 00 02 00  °°°°°°°°°°°°°°°°
0x10:  22 56 00 00 27 57 00 00 00 04 04 00 20 00 F4 03  °°°°°°°°°°°°°°°°
0x20:  07 00 00 01 00 00 00 02 00 FF 00 00 00 00 C0 00  °°°°°°°°°°°°°°°°
0x30:  40 00 F0 00 00 00 CC 01 30 FF 88 01 18 FF °° °°  °°°°°°°°°°°°°°°°

44 kHz mono (used for ap_hit_shld and the 45 zap## sounds):

1 channel; sample rate 44100 kHz; average data rate 22179 B/s (truncated from ~22179.9607073 = 44100*1024/2036);
block alignment 1024 bytes; 4 bits per sample; 2036 samples per block (= 2 + (1024 - 7)*8/4/1); standard coefficient table.
0x00:  °° °° °° °° °° °° °° °° 08 00 00 00 02 00 01 00  °°°°°°°°°°°°°°°°
0x10:  44 AC 00 00 A3 56 00 00 00 04 04 00 20 00 F4 07  °°°°°°°°°°°°°°°°
0x20:  07 00 00 01 00 00 00 02 00 FF 00 00 00 00 C0 00  °°°°°°°°°°°°°°°°
0x30:  40 00 F0 00 00 00 CC 01 30 FF 88 01 18 FF °° °°  °°°°°°°°°°°°°°°°

Only the 22.05 kHz sounds (mono and stereo) are played back correctly by the PC retail engine. The forty-six 44.1 kHz sounds are interpreted as 22.05 kHz waveforms, and therefore are played back two times slower/lower than intended.

For any other combinations of PCM or ADPCM parameters, please refer to the importing routine, HERE.

IMA ADPCM decoding ("4" flag)

If the "4" flag of the SNDD (at 0x08) is ON, then (regardless of the "4" flag), the .raw data will be interpreted as IMA ADPCM blocks, and the 50-byte format block will be mostly ignored, as well as the ".raw data size" field at 0x40.

Here is what the .dat part of the above SNDDcomguy_dth2 would have looked like in IMA4 mode:

0x00:  01 D7 08 00 01 00 00 06 04 00 00 00 00 00 01 00  °×°°°°°°°°°°°°°
0x10:  00 00 00 00 00 00 00 00 52 01 00 00 00 00 00 00  °°°°°°°°4°°°°°°°
0x20:  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  °°°°°°°°°°°°°°°°
0x30:  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  °°°°°°°°°°°°°°°°
0x40:  00 00 00 00 20 10 59 00 AD DE AD DE AD DE AD DE  °°°° °Y°°°°°°°°°
0x50:  AD DE AD DE AD DE AD DE AD DE AD DE AD DE AD DE  °°°°°°°°°°°°°°°°
The channel count field in the 50-byte "format" block (at 0x0C) is used in the same way as for a WAVE-like header.
The "block alignment" field (at 0x18) is used (somewhat counterintuitively) to store the number of IMA4 "packets":
  • for a mono IMA4 sound, packets are 34-byte blocks carrying 64 mono samples each (two bytes of header data and 64 "nibbles", or half-bytes);
  • for a stereo IMA4 sound, packets are pairs of consecutive 34-byte blocks (the 64 Left samples are stored first, then the 64 Right samples).
(The actual duration of SNDDcomguy_dth2 is, which at 22.05 kHz requires 338 64-sample blocks, hence the value 0x152 appearing at 0x18.)
Everything else in the 50-byte format block is ignored, as well as the ".raw data size" usually found at 0x40 (Oni uses the number of packets instead).

Raw PCM (no flags)

If neither the "4" nor the "8" flags are set (at 0x08 in the .dat part of the SNDD), then the .raw data is apparently copied as-is into the playback buffer.

In this "raw" playback mode, the sound will not be reproduced correctly unless it's linear PCM (Little Endian) with 16-bit sample depth, 22.05 kHz sampling rate, and a channel count consistent with the SNDD's OSGr (i.e., the metadata used by Oni's engine to set up the sound's playback).

Here is what the .dat part of the above SNDDcomguy_dth2 would have looked like in raw PCM mode:

0x00:  01 D7 08 00 01 00 00 06 00 00 00 00 00 00 00 00  °×°°°°°°°°°°°°°
0x10:  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  °°°°°°°°°°°°°°°°
0x20:  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  °°°°°°°°°°°°°°°°
0x30:  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  °°°°°°°°°°°°°°°°
0x40:  00 00 00 00 20 10 59 00 AD DE AD DE AD DE AD DE  °°°° °Y°°°°°°°°°
0x50:  AD DE AD DE AD DE AD DE AD DE AD DE AD DE AD DE  °°°°°°°°°°°°°°°°
Effect of "1" and "2" flags
It is possible that the "1" and "2" flags used to affect playback in raw PCM mode (something about swapping the .raw data to allow both for Little Endian and Big Endian PCM samples), but currently the do not seem to have any effect.

Exporting and importing tips

  • For manual converting between SNDD (PC retail or demo) and a WAVE file, see HERE.
  • For manual converting between SNDD (PC retail or Mac) and an AIFC file, see HERE.

For automatic conversion, please use a sufficiently recent version of OniSplit.

Known engine issues

Custom sample/data rates
The PC retail engine formally allows for an arbitrary sample rate (and a corresponding data rate) to be specified in the WAVfmt header, but actually the engine interprets all waveforms as 22.05 kHz.
  • If the WAVEfmt header is enabled and specifies MS ADPCM encoding (format ID 2), then the sample rate and data rate are completely ignored (you can fill those fields with zeroes or garbage, and it will still work).
  • If the WAVEfmt header is enabled and specifies PCM storage (format ID 1), then fully arbitrary (inconsistent) sample rate and data rate will cause playback glitches or interruption, whereas mutually consistent pairs ("data rate" equal to "sample rate"x"block size") are eventuall ignored. In other words, you have to specify a valid sample rate and data rate, but the engine will end up using 22.05 kHz anyway.
  • If the IMA4 header is enabled (overriding WAVEfmt), then the header only specifies the channel count and the "number of packets", and the sample/data rates are again completely ignored.
PCM playback
PCM playback is only known to work in PC retail builds, either with IMA4 and WAVEfmt headers disabled (the stream is simply copied to the output buffer, as Little-Endian 16-bit linear PCM, with the channel count specified at OSGr level) or with the WAVEfmt header enabled (in which case the stream can have a custom bit depth and channel count).
In the case of PC demo, the PCM playback fails (the engine identifies the stream as already uncompressed and skips the initialization of ACM headers, but then proceeds with decompression anyway and stops because of zero input size). This causes no problems for impulse sounds (other than silence), but results in a crash for looping permutations (the same playback keeps failing over and over).
On the Mac, the stream is interpreted as IMA4 regardless of the 0x00000001 flag, therefore if you put PCM data in the .raw, it will play back as noise.

Known data issues

PC SNDD data
The MS ADPCM data used by Vanilla Oni on Windows (both retail and demo) is somewhat coarser (lossier) than the IMA4 ADPCM used on Mac. This is because of the much larger block size, and how the same predictor must be used for the whole block: whenever a block spans both high- and low-amplitude samples, the predictor adapts to the higher amplitudes, and the low-amplitude resolution is lost.
As a minor issue, the lack of an exact sample count (similar to a WAVE's "fact") makes it impossible to specify an odd number of samples for a mono block (because there is no way to tell if the last byte's second nibble counts or not). It is also impossible to have only one sample in the last block, be it for mono stereo (because the block header reads as two samples by default).
Mac SNDD data
Unlike Oni's implementation of MS ADPCM, which cuts off the last block after the last actual sample, IMA4 data consists of full 64-sample blocks, with no way to determine the actual sample count other than by comparing with the same sound from PC Oni. (The "padding" of IMA4 sounds is not always zero, and even if it was, truncation based on trailing zeroes would be somewhat arbitrary.) The padding of IMA4 samples to multiples of 64 leads to silences at the end of Mac sounds that can be up to 3 milliseconds long. This is not a problem for impulse sounds or looping sounds that are quiet near the end, but for loud music (e.g. the main menu's "Trailer" theme) the gap is noticeable. It has been confirmed that the gap is actually heard in Mac Oni, apparently without bothering anyone.
As a hypothetical fix, the Oni engine could implement a sample count parameter (similar to a WAVE file's "fact"), or truncate the last 64-sample block after the last actual sample, upon encoding (the latter is slightly less straightforward for stereo – because there are two last blocks, one for each channel – but still not a big problem).
Mac sound data also seems to suffer from encoding artifacts: there are spurious transients at the start of waveforms that prevent ambients and music from looping seamlessly even when cut at the right length. Unlike the padding, this cannot be remedied at all, therefore if one wishes to produce seamless tracks from Oni data (e.g. music) it is recommended to turn to PC SNDDs, which have no looping issues (but are slightly lossier because of the larger block size, as mentioned above).

Modern support

OniSplit

Newer releases (OniSplit v0.9.99.3 and newer) include an implementation of the MS ADPCM and IMA4 codecs, along with the ability to generate .dat/.raw./sep game data compatible with the PC-demo based OniX engine. The codecs allow OniSplit to transcode from Mac's IMA4 or from 44.1 kHz MS ADPCM to standard 22.05 kHz MS ADPCM. PCM is also supported both ways (both as .wav output coming from IMA4 or MS ADPCM, or as uncompressed SNDD intended for the PC retail or demo engines). Finally, for exotic sample rates, there is an option to store the waveform as-is (without resampling) and merely report the appropriate rate multiplier that can be used in OSGr to adjust the speed/pitch upon playback.

Older releases (OniSplit v0.9.99.2 and older) did not support ADPCM encoding or decoding, so there was no way to transcode between IMA4, MS ADPCM and PCM. Generating instance files for the demo engine was not supported either.

The hybrid SNDD format (aligned with OniX's planned features) has not been implemented in OniSplit yet. The recently discovered PC retail engine features (IMA4 support, or default PCM support) are also not covered by OniSplit at the time of writing.

OniX

Starting with v1.1, OniX will likely support all three standard streams (IMA4, MS ADPCM and PCM) with their default encoding/storage settings:

  • for IMA4, 32-byte blocks with 64 samples per block (interleaved Left-channel and Right-channel blocks if stereo), sample rate 22.05 kHz;
  • for MS ADPCM, 512-byte blocks for mono, 1024-byte blocks for stereo, 1012 samples per block in both cases, sample rate 22.05 kHz;
  • for PCM, signed linear 16-bit samples, Little Endian storage, sample rate 22.05 kHz.

The engine will determine between the three types of streams using flags in the short SNDD header. Possibly another flag will allow for doubled sample rate (44.1 kHz); in this configuration the default block size will probably be 1024 bytes for mono and 2048 bytes for stereo, with 2036 samples per block in each case.

Finally, even with a short SNDD header, it is possible for OniX to read a custom WAVEfmt chunk just like the PC retail engine does, by putting the chunk at the start of the .raw part and announcing its presence and/or size through another flag and/or the unused uint at 0x0E. The typical size of this ".raw header" will be 16 bytes for PCM and 50 bytes for ADPCM (the use of other WAVE formats will probably be discouraged).

Alternatively, both the flags and the uint at 0x0E can be used to specify a custom sample rate and/or block size (either as fully custom values or as power-of-two multiplicative factors), without the need for a detailed WAVEfmt header. Still, it is probably easiest to either adhere to the standard parameters (without too many extra flags) or go fully custom and read all the parameters from a standard-compliant WAVEfmt header.

Notes

  1. ↑ 1.0 1.1 As an example, on PC (both demo and retail), SNDDmus_ot7.aif consists of 152360 samples, which at 22.05 kHz corresponds to 6.90975 seconds, or 414.585 ticks; the duration, however, is indicated as 414 ticks and not 415. In other words, "duration" corresponds to the number of whole game ticks spanned by the sound's playback.
  2. ↑ If a SNDD misses the "1" flag ("compressed"), the PC demo engine does identify the stream as already uncompressed (PCM samples) and skips the initialization phase of the decompression routine, but then proceeds with decompression anyway, and immediately stops because of zero input size.
ONI BINARY DATA
QTNA << Other file types >> StNA
SNDD : Sound Data
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