mabl
Posts: 4
Joined: Sun Jan 19, 2014 10:57 am

ALSA Multi-channel output

Sun Jan 19, 2014 11:58 am

Hello,

I want to set up my rp as pulse audio headless network server, using a 5.1 channel configuration over HDMI. I have pulse audio running and "./hello_audio.bin 1 6" as well as "omxplayer --adev hdmi --layout 5.1" work. So far so good.

The showstopper I hit now, is that I do not get Pulseaudio to detect a multi-channel ALSA output device. As far as I understood, this is actually because the ALSA driver does not support multi-channel. Is there a reason for this? Would patching the snd-bcm2835 driver be easy? I saw that ".channels_max = 2" is defined in "bcm2835-pcm.c". Would changing that value be enough? :twisted:

I'd be really grateful for hints.

koalo
Posts: 121
Joined: Mon Feb 04, 2013 4:02 pm

Re: ALSA Multi-channel output

Sun Jan 19, 2014 8:33 pm

I have never used the HDMI interface for transmitting audio, but as far as I know the snd-bcm2835 module is only for the headphones jack on the board and has nothing to do with HDMI.

mabl
Posts: 4
Joined: Sun Jan 19, 2014 10:57 am

Re: ALSA Multi-channel output

Sun Jan 19, 2014 8:40 pm

Hi koalo,

I have sound going over HDMI working with ALSA already - just not more than two channels. I'm currently trying to compile a patched version - maybe I'm lucky and it just works. I'll report my findings here.

mabl
Posts: 4
Joined: Sun Jan 19, 2014 10:57 am

Re: ALSA Multi-channel output

Sun Jan 19, 2014 9:04 pm

Ok... Sadly it looks like it did not work. Too bad - especially, since the rp is capable of doing this. It's just that the alsa driver sucks :(

mabl
Posts: 4
Joined: Sun Jan 19, 2014 10:57 am

Re: ALSA Multi-channel output

Fri Jan 24, 2014 8:44 pm

I'm still searching for a solution to play multiple audio channels over ALSA. It's quite frustrating, since omxplayer shows that it is indeed possible from a hardware point of view.

strangerng
Posts: 5
Joined: Wed Apr 23, 2014 9:46 pm

Re: ALSA Multi-channel output

Tue May 13, 2014 3:57 pm

I've noticed a strange thing... RP can play mutichannel with ALSA but in a very strange way.
I have Volumio ( basicly minimal debian installation for MPD service) installed.
I've renamed few of my multichannel (DTS) WAV files to flac and passed them to mpd and guess what?))
I had my reciever telling me DTS passthrough audio signal and real 5.1 sound.
This didn't work with AC3 (Dolby Digital) files and so on...
So this is very poor workaround if someone want to have multichannel... but it works)))

I've tried to send output of MPD to *.fifo and open this file with omxplayer. Looks like OMX can't handle it....

The thing I'm thinking about now is to pass the mpd output to pulseaudio and make it send a passthrough audio signal to HDMI...

MABL, do you have any working config for pulseaudio to make passthrough?

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