2014/1/12 Takashi Sakamoto <o-takashi at sakamocchi.jp>: > Then I debug PulseAudio/libasound in a point of 'how to open ALSA PCM > handle'. I have an presumption that 'plug' plugin can upscale channels > correctly if PulseAudio open 'plug:hw' device as the same way as > normal-aplay open. > > As a result, I got a conviction that 'SND_PCM_NO_AUTO_CHANNELS' flag for > snd_pcm_open() disables upscaling. This is documented at http://www.alsa-project.org/alsa-doc/alsa-lib/group___p_c_m.html#ga64fa40b556374dabe40d4874242fee19 By "forced channel conversion" they mean the "route" ALSA plugin. See how it is done in /usr/share/alsa/cards/ICE1712.conf , which is similar to your use case. Specifically, they try to upscale everything to 10 channels, because this is what this hardware supports directly. -- Alexander E. Patrakov
