[FFmpeg-user] ADPCM block size for XAudio

Carl Eugen Hoyos ceffmpeg at gmail.com
Fri Feb 9 03:31:17 EET 2018

2018-02-08 8:02 GMT+01:00 Martin Wahnschaffe <wahnschaffe at gmail.com>:
>> I changed the BLKSIZE constant to 512 and it still didn't work with XAudio.
>> So I took a closer look at the code. Turns out that the BLKSIZE constant
>> is actually used to set the block_align value. Microsoft measues the size
>> of a block in samples (
>> https://msdn.microsoft.com/de-de/library/windows/desktop/ee415711(v=vs.85).aspx).
>> This seems to be different from the block_align used in adpcmenc.c. My
>> impression is that frame_size is instead what has to be between 32 and 512.
>> I tested this by setting BLKSIZE to 70. With my mono wave file this
>> resulted in a frame_size of 128 = (BLKSIZE - 7 * avctx->channels) * 2 /
>> avctx->channels + 2.
>> The resulting compressed file is working with XAudio.
>> I am very unsure if this is the right thing to do.
> So what should we do about this? Any chance to introduce ADPCM XAudio
> compatibility into ffmpeg?

What's wrong with a parameter for blksize (with frame_size value)?

> There is a lot of games that could profit from this.

Could you elaborate? I think I don't understand...

Carl Eugen

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