5.1 USB audio

1st Official Post

    I have an acer revo 3600 which I've been using for the past 9 years with mythfrontend (on gentoo). It uses the nvidia Ion chipset, is fairly low power and is good enough to play anything I have. I have a USB sound card which shows up under lsusb as: ID 0d8c:0006 C-Media Electronics, Inc. Storm HP-USB500 5.1 Headset

    I fancied a change after all this time and wanted youtube, so I put kodi on it with Ubuntu. This turned out to be a little flaky, so I thought I'd try libreelec which so far has been excellent but with one caveat. Audio.

    With myth I used alsa, but had to re-map the speakers to get the correct output to the correct speakers. Ubuntu uses pulse, so I mapped the speakers with that. In both myth and ubuntu/kodi I could get audio in any format decoded and sent to the correct speakers.

    Now with libreelec I can only get stereo audio from youtube and mpgts recordings, AC3 etc produce no sound at all, and even if they did I suspect it'd come from the wrong places. I notice the root fs is squashfs and hence read only. Is there any way for me to use my old .asoundrc (or even a new configuration) successfully with alsa and get everything working as it should?

    This is the working (but not on libreelec) .asoundrc :

    and the modification to pulse's default.pa:

    Code
    load-module module-remap-sink sink_name=fix-surround master=0 channels=8 master_channel_map=front-left,front-right,rear-left,rear-right,front-center,lfe,side-left,side-right channel_map=front-left,front-right,lfe,front-center,rear-right,rear-left,side-left,side-right
set-default-sink fix-surround

    Kodi is very nice and I really don't want to feel I have to go back to mythfrontend to get both decent sound and a stable system.

    No dice, still stereo or nothing.

    I did a minimal image ubuntu install and now running kodi as a service with no WM. Solid so far and with the added bonus of proper sound again. If I used SP/DIF or only had stereo audio then LE would be for me, but sadly it's not.

    Longshot, but I'm trying to get this device working properly and I'm getting just the L C R channels too much like is described. Any chance you solved this? Thx

    same thing here, been all over the audio drivers and can't find meaningful info from logs.

    Stereo (2 channels) playback totally fine through USB device, LibreELEC correctly names the device, everything as expected. The moment I try any surround playback, DTS, linear PCM, playback disappears.

    maybe there is some licensing thing with decoding the surrounnd formats? I thought hardware manufacturers (AV receivers) had to pay dolby or whoever - but it's trivial to decode in software

    maybe we should flag in github?

    • Official Post
    Quote from doobedoobedo

    I did a minimal image ubuntu install and now running kodi as a service with no WM. Solid so far and with the added bonus of proper sound again.

    That's a proof of my theory. I think it's a timing issue. The more processing the PC has to deal with, the longer the USB latency. At some cutting point, some audio data will be dropped, because there is no chance to deliver in time.

    I'm currently running a real-time-kernel Ubuntu for music production with a connected USB-MIDI controller. The USB latency difference between a real-time / non-real-time system is significant. I know what I'm talking about.

    -> Stay away from high speed USB audio if you run a regular (non-real-time-kernel) Linux.