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OBD:SNDD/wav: Difference between revisions
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:From the "samples per block" follows the average rate (at 0x1C). From the actual number of samples (at 0x4E) follows the number of ADPCM blocks required to store the waveform, and therefore the data size at (0x56), a multiple of "block size", which in turn affects the total RIFF size at 0x04. | :From the "samples per block" follows the average rate (at 0x1C). From the actual number of samples (at 0x4E) follows the number of ADPCM blocks required to store the waveform, and therefore the data size at (0x56), a multiple of "block size", which in turn affects the total RIFF size at 0x04. | ||
;"fact" section VS truncated data | ;"fact" section VS truncated data | ||
:It is ''not'' standard-compliant to truncate the final ADPCM block after the last actual sample like Oni does. The WAVE file is expected to contain ''whole'' ADPCM blocks (usually padded with zeroes), and the exact number of actual samples is specified in the "fact" section. This is not very space-efficient, but it allows a waveform to have a completely arbitrary number of samples. With Oni's truncated data and lack of an explicit sample count, it is impossible to specify an odd-numbered count of mono samples (because the bytes of mono ADPCM blocks consist of consecutive same-channel nibbles, and there is no way to tell whether the last nibble counts or not). Also, Oni can only truncate after the header of an ADPCM block, therefore the two explicitly stored samples | :It is ''not'' standard-compliant to truncate the final ADPCM block after the last actual sample like Oni does. The WAVE file is expected to contain ''whole'' ADPCM blocks (usually padded with zeroes), and the exact number of actual samples is specified in the "fact" section. This is not very space-efficient, but it allows a waveform to have a completely arbitrary number of samples. With Oni's truncated data and lack of an explicit sample count, it is impossible to specify an odd-numbered count of mono samples (because the bytes of mono ADPCM blocks consist of consecutive same-channel nibbles, and there is no way to tell whether the last nibble counts or not). Also, Oni can only truncate after the header of an ADPCM block, therefore the two explicitly stored samples in the header are always played, whereas "fact" can be used to indicate that only the first sample is actual waveform data, and the other is a dummy. | ||
;Data size | ;Data size | ||
:The size at 0x56 is the size of the raw data that starts at 0x5A, which consists of whole ADPCM blocks and will need to be truncated after the last actual sample for use in an Oni SNDD instance. If the data is not truncated, Oni will determine the sample count from the padded data size, and there will be a noticeable silence (up to 46 milliseconds, or almost 3 game ticks, at 22.05 kHz and for 1012 samples per block) – not a problem for impulse sounds, but definitely not recommendable for ambients or music. | :The size at 0x56 is the size of the raw data that starts at 0x5A, which consists of whole ADPCM blocks and will need to be truncated after the last actual sample for use in an Oni SNDD instance. If the data is not truncated, Oni will determine the sample count from the padded data size, and there will be a noticeable silence (up to 46 milliseconds, or almost 3 game ticks, at 22.05 kHz and for 1012 samples per block) – not a problem for impulse sounds, but definitely not recommendable for ambients or music. | ||
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The PC retail engine is more flexible since it has a 50-byte format section specifically intended to receive the "fmt " chunk of a MS ADPCM .wav file along will all the non-trivial ADPCM settings. This format section is activated with the 0x00000008 flag, provided that the 0x00000004 flag is OFF (this "4" flag overrides the "8" flag and forces the interpretation of the data as IMA4 ADPCM). | The PC retail engine is more flexible since it has a 50-byte format section specifically intended to receive the "fmt " chunk of a MS ADPCM .wav file along will all the non-trivial ADPCM settings. This format section is activated with the 0x00000008 flag, provided that the 0x00000004 flag is OFF (this "4" flag overrides the "8" flag and forces the interpretation of the data as IMA4 ADPCM). | ||
The 50-byte format section in the SNDD can also be used to store the shorter "fmt " chunk of | The 50-byte format section in the SNDD can also be used to store the shorter "fmt " chunk of PCM .wav files, and this is the recommended procedure, as opposed to using the "raw PCM" functionality of PC retail SNDD (if you remove the 0x00000008 flag, then the format header is completely disabled and the .raw SNDD data is interpreted as 22.05 kHz PCM, using the channel count specified at OSGr level; don't do that, and just use the "8" flag). | ||
;Copying the .raw data | ;Copying the .raw data | ||
:For PCM, just refer to the "PCM" template above: copy the data that starts at 0x2C in the WAVE file (its size can be found at 0x28, but it reaches to the end of the file anyway since there is no padding). Copy the data to the SNDD's .raw part, store the address at 0xC4 in the SNDD's .dat part and the size at 0xC0. | :For PCM, just refer to the "PCM" template above: copy the data that starts at 0x2C in the WAVE file (its size can be found at 0x28, but it reaches to the end of the file anyway since there is no padding). Copy the data to the SNDD's .raw part, store the address at 0xC4 in the SNDD's .dat part and the size at 0xC0. | ||