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Have you tested surround21?

Yes, front speakers work fine, however LFE doesn't seem to work. Instead

when I try to test LFE (from sound UI) I have weird noise in one of rear speakers. There are no such problems with any other mode though (I see that officially only 5.1 mode is supported, however 4.1, 5.0 and 5.1 all work fine), I decided to leave 2.1 mode for now, not sure whose fault is that.

http://git.alsa-project.org/?p=alsa-lib.git;a=commitdiff;h=3c4a22ea49a881cdb...

It is strange that pcm state is open

( 0.089| 0.001) D: [pulseaudio] alsa-mixer.c: Looking at profile output:analog-surround-21 ( 0.089| 0.000) D: [pulseaudio] alsa-mixer.c: Checking for playback on Analog Surround 2.1 (analog-surround-21) ( 0.089| 0.000) D: [pulseaudio] alsa-util.c: Trying surround21:1 with SND_PCM_NO_AUTO_FORMAT ... ( 0.089| 0.000) I: [pulseaudio] (alsa-lib)pcm_hw.c: Invalid PCM state for chmap_get: OPEN

( 0.089| 0.000) D: [pulseaudio] alsa-util.c: Managed to open surround21:1 ( 0.089| 0.000) I: [pulseaudio] alsa-util.c: Disabling tsched mode since BATCH flag is set ( 0.089| 0.000) D: [pulseaudio] alsa-util.c: Maximum hw buffer size is 1213 ms ( 0.090| 0.000) D: [pulseaudio] alsa-util.c: Set buffer size first (to 4797 samples), period size second (to 1199 samples). ( 0.090| 0.000) I: [pulseaudio] alsa-util.c: Device surround21:1 doesn't support 44100 Hz, changed to 48000 Hz. ( 0.090| 0.000) D: [pulseaudio] alsa-mixer.c: Profile output:analog-surround-21 supported.