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OBD:SNDD: Difference between revisions
→WAV files: fact
(→IMA ADPCM: duh) |
(→WAV files: fact) |
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{{OBDtr| 0x4A | int32 |C8FFC8| 56 28 00 00 | 10326 | size of the following wav data in bytes (<nowiki>=</nowiki> size of the .raw part) }} | {{OBDtr| 0x4A | int32 |C8FFC8| 56 28 00 00 | 10326 | size of the following wav data in bytes (<nowiki>=</nowiki> size of the .raw part) }} | ||
|} | |} | ||
The above is not 100% consistent with the WAVE storage rules, because it allows for a completely arbitrary "data" size. Microsoft ADPCM data is supposed to be stored as a number of fixed-size blocks (in Oni, each block is either 512 bytes for 22.05kHz mono, or 1024 bytes for 22.05kHz stereo and 44.1kHz mono) and, according to the standard, the last block, even if incomplete, must be stored in its entirety, and the "data" size must be a multiple of the block size. Thus, for the above example (22.05kHz mono), the "data" size should be increased from 10326 to 10752=21x512, and 426 empty bytes should be added as padding, so that there are 21 complete data blocks. The standard way to specify the ''actual'' number of samples is to add a "fact" section to the WAVE header, like this: | |||
{{Table}} | |||
{{OBDth}} | |||
{{OBDtrBK|1=Complete ADPCM wav format header}} | |||
{{OBDtr| 0x00 | char[4] |FF0000| 52 49 46 46 | RIFF | identifier for the "IBM/Microsoft RIFF" standard }} | |||
{{OBDtr| 0x04 | int32 |FFFF00| 9C 28 00 00 | 10396 | size of the file from 0x08 to the end (<nowiki>=</nowiki> size of the .raw part + 70 bytes) }} | |||
{{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 wav format header section }} | |||
{{OBDtr| 0x10 | int32 |FFC8C8| 32 00 00 00 | 50 | wave format header size }} | |||
{{OBDtr| 0x14 | block[50]|FFC8C8| | | [[OBD:SNDD/wav|wav header]] }} | |||
{{OBDtr| 0x46 | char[4] |FFFFC8| 66 61 63 74 | fact | identifier announcing the following "fact" section }} | |||
{{OBDtr| 0x4A | int32 |FFFFC8| 04 00 00 00 | 4 | size of the following "fact" section in bytes }} | |||
{{OBDtr| 0x4E | int32 |C8FFC8| B0 4F 00 00 | 20400 | actual number of samples (see below for calculation) }} | |||
{{OBDtr| 0x52 | char[4] |FFFFC8| 64 61 74 61 | data | identifier announcing the following wav data }} | |||
{{OBDtr| 0x56 | int32 |C8FFC8| 00 2A 00 00 | 10752 | size of the following wav data in bytes (<nowiki>=</nowiki> size of the .raw part + 426 empty bytes) }} | |||
|} | |||
The actual number of samples is implied from the actual data size (size of the .raw part) and [[OBD:SNDD/wav|wav header]] properties as follows: | |||
* n_whole_blocks = floor(raw_size/block_size); '''// EXAMPLE: floor(10326/512) = 20''' | |||
* last_block_size = raw_size - whole_blocks*block_size; '''// EXAMPLE: 10326 - 20x512 = 86''' | |||
* last_block_samples = (last_block_size - 7*n_channels)*(8/bits_per_sample/n_channels) + 2; '''// EXAMPLE: (86 - 7)*(8/4) + 2 = 160''' | |||
* n_samples = n_whole_blocks*samples_per_block + last_block_samples; '''// EXAMPLE: 20*1012 + 160 = 20400''' | |||
---- | ---- | ||
====AIF files==== | ====AIF files==== | ||
*Write "FORM" | *Write "FORM" | ||