OBD:SNDD

ONI BINARY DATA QTNA << Other file types >> StNA SNDD : Sound Data switch to XML:SNDD page Overview @ Oni Stuff

.dat

There are 2 different formats used by the SNDD files.

PC retail

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

Offset	Type	Raw Hex	Value	Description
0x00	res_id	01 D7 08 00	2263	02263-comguy_dth2.aif.SNDD
0x04	lev_id	01 00 00 06	3	level 3
0x08	int32	08 00 00 00	8	flags 1 - 2 - 4 - 8 - ADPCM compressed
0x0C	block[50]			wav header
0x3E	int16	37 00	55	duration in 1/60 seconds
0x40	int32	56 28 00 00	10326	size of the part in the raw file in bytes
0x44	offset	20 10 59 00	00 59 10 20	at this position starts the part in the raw file
0x48	char[24]	AD DE	dead	unused

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PC demo and Mac

The Mac version and the PC demo version use a simpler format. It appears that there is no support for different sample rates (all sounds are sampled at 22050 Hz).

Offset	Type	Raw Hex	Value	Description
0x00	res_id	01 D6 08 00	2262	02262-comguy_dth2.aif.SNDD
0x04	lev_id	01 00 00 06	3	level 3
0x08	int32	01 00 00 00	1	"number of channels" (can be 1 for 1 channel or 3 for 2 channels)
0x0C	int32	37 00 00 00	55	duration in 1/60 seconds
0x10	int32	5E 2A 00 00	10846	size of the part in the raw file in bytes
0x14	offset	00 B1 01 00	00 01 B1 00	at this position starts the part in the raw file
0x18	char[8]	AD DE	dead	unused

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raw

The raw data part of a SNDD file contains the actual audio sample blocks without any other headers (other than block headers).

Exporting and importing tips

To create a wav/aif file one needs to write a file header like below and then write the contents of the raw data part.

WAV files

• Write "RIFF"
• add the size of the part in the raw file + 70 bytes
• write "WAVE"
• write "fmt "
• write 50
• write the wav header
• write "data"
• add the size of the part in the raw file
• add the raw file data
• save it as a wav file.

Offset	Type	Raw Hex	Value	Description
Complete ADPCM wav format header (black outline)
0x00	char[4]	52 49 46 46	RIFF	identifier for the "IBM/Microsoft RIFF" standard
0x04	int32	9C 28 00 00	10396	size of the file from 0x08 to the end (= size of the .raw part + 70 bytes)
0x08	char[4]	57 41 56 45	WAVE	identifier for the "WAVE" format
0x0C	char[4]	66 6D 74 20	fmt	identifier announcing the following wav format header
0x10	int32	32 00 00 00	50	wave format header size
0x14	block[50]			wav header
0x46	char[4]	64 61 74 61	data	identifier announcing the following wav data
0x4A	int32	56 28 00 00	10326	size of the following wav data in bytes (= size of the .raw part)

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AIF files

• Write "FORM"
• add the size of the part in the raw file + 50 bytes
• write "AIFC"
• write "COMM "
• add the aif header + calculate its sample rate (always 22)
• write "SSND"
• add the size of the part in the raw file + 8 bytes
• add 8 zero bytes
• add the raw file data and save it as an aif file.

Note the Big Endian order

Offset	Type	Raw Hex	Value	Description
Complete aif format header (black outline)
0x00	char[4]	46 4F 52 4D	FORM	identifier for the "EA IFF 85" standard
0x04	int32	00 00 2A 90	10896	size of the file from 0x08 to the end (= size of the .raw part + 50 bytes)
0x08	char[4]	41 49 46 43	AIFC	identifier for the "AIFC" format (compressed aif file)
0x0C	char[4]	43 4F 4D 4D	COMM	identifier announcing the following aif format header
0x10	block[26]			aif header
0x2A	char[4]	53 53 4E 44	SSND	identifier announcing the following aif data
0x2E	int32	00 00 2A 66	10854	size of the file from 0x32 to the end (= size of the .raw part + 8 bytes)
0x32	int32	00 00 00 00	0	offset; determines where the first sample in the data starts; in Oni it's always zero
0x36	int32	00 00 00 00	0	block size; used in conjunction with offset for block-aligning data; in Oni it's always zero

ADPCM format details

MS ADPCM - PC retail

For an overview of the ADPCM algorithm (if interested), see HERE.

The MS ADPCM data has 512- or 1024-byte blocks (512 bytes for 22.05kHz mono, 1024 bytes for 22.05kHz stereo and 44.1kHz 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 22.05kHz mono or stereo, and 2034 more samples in the case of 44.1kHz mono)

Thus the total number of samples per block (including the two in the header) is 1012 for 22.05kHz (mono or stereo) and 2036 for 44.1kHz mono.

The final block in the file can be incomplete (the decoder can infer this from the block size and raw data size).

IMA ADPCM (IMA4) - Mac and PC demo

For an overview of the IMA ADPCM algorithm and IMA4 header (if interested), see 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 first two bytes of each block are used to set the initial the predictor (upper 9 bits) and step (lower 7 bits) for decoding the block's samples.

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 announced in any way: the final blocks are stored in their entirety, with no way to tell how much of it is actual data.

For this reason, identical sounds do not have the same sample count on PC retail and Mac/demo. As an example, here are the stats for some stereo sounds ("atm_cl05" ambient):

SNDD name (and frame count) PC retail Mac/demo difference SNDDatm_cl05_in 100 frames = 1.6667 seconds ~= 36750 samples (@22.05kHz) 0x916C = 37228 = 36x1024 + 364 bytes = 36x1012 + 352 = 36784 stereo samples = 1.668208616780045 s (@22.05kHz) 0x98BC = 39100 = 1150x34 bytes = 575x64 = 36800 stereo samples = 1.668934240362812 s (@22.05kHz) As compared to PC retail, Mac/demo has 16 extra samples at the end (i.e., the last 8 bytes of the last two blocks). SNDDatm_cl05_lp1 897 frames = 14.95 seconds ~= 329647.5 samples (@22.05kHz) 0x5172A = 333610 = 325x1024 + 810 bytes = 325x1012 + 798 = 329698 stereo samples = 14.95229024943311 s (@22.05kHz) 0x55880 = 350336 = 10304x34 bytes = 5152x64 = 329728 stereo samples = 14.95365079365079 s (@22.05kHz) As compared to PC retail, Mac/demo has 30 extra samples at the end (i.e., the last 15 bytes of the last two blocks) SNDDatm_cl05_lp2 795 frames = 13.25 seconds ~= 292162.5 samples (@22.05kHz) 0x48334 = 295732 = 288x1024 + 820 bytes = 288x1012 + 808 = 292264 stereo samples = 13.25460317460317 s (@22.05kHz) 0x4BD1C = 310556 = 9134x34 bytes = 4567x64 = 292288 stereo samples = 13.25569160997732 s (@22.05kHz) As compared to PC retail, Mac/demo has 24 extra samples at the end (i.e., the last 12 bytes of the last two blocks) SNDDatm_cl05_lp3 428 frames = 7.133333 seconds ~= 157290 samples (@22.05kHz) 0x26F1 = 159506 = 155x1024 + 786 bytes = 155x1012 + 774 = 157634 stereo samples = 7.148934240362812 s (@22.05kHz) 0x28E80 = 167552 = 4928x34 bytes = 2464x64 = 157696 stereo samples = 7.151746031746032 s (@22.05kHz) As compared to PC retail, Mac/demo has 62 extra samples at the end (i.e., the last 31 bytes of the last two blocks) SNDDatm_cl05_lp4 478 frames = 7.9666667 seconds ~= 175665 samples (@22.05kHz) 0x2B7BE = 178110 = 173x1024 + 958 bytes = 173x1012 + 946 = 176022 stereo samples = 7.982857142857143 s (@22.05kHz) 0x2DABC = 187068 = 5502x34 bytes = 2751x64 = 176064 stereo samples = 7.984761904761905 s (@22.05kHz) As compared to PC retail, Mac/demo has 42 extra samples at the end (i.e., the last 21 bytes of the last two blocks) SNDDatm_cl05_out 109 frames = 1.816667 seconds ~= 40057.5 samples (@22.05kHz) 0x9E7A = 40570 = 39x1024 + 634 bytes =39x1012 + 622 = 40090 stereo samples = 1.818140589569161 s (@22.05kHz) 0xA68C = 42636 = 1254x34 bytes = 627x64 = 40128 stereo samples = 1.819863945578231 s (@22.05kHz) As compared to PC retail, Mac/demo has 38 extra samples at the end (i.e., the last 19 bytes of the last two blocks)

By looking at the end of the Mac/demo 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). It is not clear how the Mac (or PC demo) engine detects these trailing samples and cuts them off (this is important when playing a sequence, e.g. music or ambient loops, see "looping issues" below).

Possibly Mac/demo Oni just looks at the approximate length of each SNDD in frames (or game ticks, i.e., 1/60th of a second), which is listed in each SNDD's header and, once the announced frame count has been reached for the currently playing sound, starts playback on the next sound in the sequence. Depending on the hardware/software implementation of the audio pipelines, this logic can either interrupt the currently playing sound, or cause a slight overlap/crossfade between the current sound and the next. It is possible that PC retail Oni actually does the same, i.e., segments of a sequence are dispatched to the OS based on the frame count of the previous segment, rather than based on its actual play time (sample count).

Another theoretical possibility is that, in the case of IMA4 ADPCM, an illegal step index (outside the expected 0-88 range) is used to signify the end of the stream. Decoders typically resolve this by forcing an out-of-bounds step index into the 0-88 interval, but perhaps a custom decoder can interrupt the stream instead. However, this would be very non-standard behavior, and would only be feasible if the decompressed audio stream is put together inside Oni's engine, rather than deferred to the OS. Therefore it is more likely that Oni dispatches each segment to the OS based on the frame count; the OS receives the ADPCM-compressed data, decompresses it and plays it back; the overlap/crossfade/interruption of the currently playing segment is handled at OS level.

Looping issues

As detailed above, ADPCM data is stored in blocks, but the actual sound data does not necessarily end exactly at the end of a block. This is true both for MS ADPCM (PC retail) and IMA4 ADPCM (Mac and PC demo), but is especially noticeable for the comparatively large blocks of MS ADPCM, where the padding can be as large as ~1010 samples, i.e., a ~46-millisecond silence in the case of 22.05kHz (for IMA4, the biggest possible gap is 63 samples, or ~3 milliseconds).

MS ADPCM

Although the final block of a MS ADPCM file is stored in incomplete form (with only the actual samples and no padding), the standard decoding behavior (e.g., in an audio editor) is to automatically add the padding up to the end of the last block of an ADPCM-compressed WAV, creating a silence at the end of the imported audio. This artificial silence can be a problem if one wants to join SNDDs that are supposed to play seamlessly one after another (e.g., a musical or ambient sequence).

The solution is to use some alternative tools, which are more flexible about incomplete MS ADPCM blocks:

• For Sox, padding is disabled by default when joining several files.
• For ffmpeg, padding can be disabled as an optional setting.

IMA ADPCM

In the case of IMA ADPCM, the padding is actually present in the stored audio, so it is impossible (both for OniSplit and for a third-party converter) to automatically trim it down to just the relevant audio data. In fact, just by looking at the Mac/demo SNDD itself, there is no way to tell how many of the trailing samples need to be cut for a truly seamless transition.

There are two solutions - an approximate one and an exact one:

1. As an approximation, look up the frame count announced in the SNDD's header (using a hex viewer or an XML dump), divide that by 60 to get the length of the clip in seconds, and multiply by the sample rate 22.05kHz. You will get the number of samples (and the corresponding delay in seconds) that are actually played back by Oni before starting the next sound in the sequence. You can replicate this delay with ffmpeg, Sox, or the audio editor of your choice. A cross-fade between the two clips in the overlapping region should sound best. You can also examine the samples near the approximate transition time, and "manually" determine where the actual samples end and the padding begins.
2. As an exact solution, look up the sample count of an equivalent MS ADPCM file from a PC retail version of Oni. Padding should only be a problem for non-localized music and ambients, so the language version shouldn't matter. The electric "zap" sounds (which are sampled at 44.1kHz in PC retail Oni) are also not loopable, so you should be able to find a 22.05kHz sound with a intuitive sample count. It will be somewhat smaller than the raw sample count of the IMA4 ADPCM, because of the padding (see the atm_cl05 example above for a comparison). Once you know the actual sample count, use ffmpeg to convert the .aif file to .wav (either PCM or ADPCM), keeping only the actual samples and trimming out the padding. Then, use Sox or ffmpeg to seamlessly join the .wav files as you would for regular MS ADPCM files (see above).

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ONI BINARY DATA
QTNA << Other file types >> StNA
SNDD : Sound Data
Generic file