Re: [alsa-devel] [PATCH] pcm: 2nd round of pcm_misc DSD fixes

At Fri, 15 Aug 2014 15:02:35 +0600, Alexander E. Patrakov wrote:

15.08.2014 12:43, Jurgen Kramer wrote:

...

Functions 'snd_pcm_format_silence_64' and 'snd_pcm_format_size' also need to be able to handle the DSD formats.

0 is not a DSD silence value. It is the most negative value, similar to -32768 for S16 samples. We need something that will average to zero.

ffmpeg uses a repeating pattern of 0x69 here, with this comment:

     /* 0x69 = 01101001
      * This pattern "on repeat" makes a low energy 352.8 kHz tone
      * and a high energy 1.0584 MHz tone which should be filtered
      * out completely by any playback system --> silence
      */

https://ffmpeg.org/pipermail/ffmpeg-cvslog/2014-April/076427.html

Good point. We need a fix in the kernel side, too.

Takashi