[Buildroot] Driver for C-Media Electronics, Inc. CM106 based usb audio device?

Lou Crittenden loucrittenden63 at gmail.com
Thu Feb 26 02:09:39 UTC 2015

On the raspbian image, I am able to run yes > /dev/null multiple times in
multiple terminals to max out the processor while mplayer was playing in
another tty and it doesn't skip a beat. I again wonder if it's the kernel
configuration in buildroot?

On Wed, Feb 25, 2015 at 7:55 PM, Lou Crittenden <loucrittenden63 at gmail.com>

> Oh, I also forgot to mention I am playing mplayer in the buildroot setup
> in the console, as I still don't have a gui yet.
> On Wed, Feb 25, 2015 at 7:53 PM, Lou Crittenden <loucrittenden63 at gmail.com
> > wrote:
>> >I was able to compile and run a rockbox version on RPi/buildroot, but
>> still
>> > without audio file playing...
>> Awesome! Can I see it?
>> I was able to run mplayer with no options in a terminal within the
>> raspbian image that came with my waveshare device and it didn't have a bit
>> of problems with the audio. It sounded great actually.
>> You're probably right on the resource part, and I believe the buildroot
>> kernel has a lot to do with it, but the raspbian kernel didn't have that
>> issue at all, but of course it just takes a long time to boot compared to
>> buildroot. I want to use the isolator to isolate the usb sound device from
>> the background zipper noises, pops, buzzes, whining, and other garbage from
>> the main computer board that happens when for example you are scrolling a
>> page or leds on the board blink.
>> I have included a sample of what I am running into as far as the audio.
>> This was with the commands:
>> # cd /media/usb0 (this thumbdrive is where my music is located)
>> # mplayer *
>> and with my usb sound device plugged in. It doesn't do that with the
>> onboard card, though (even though it sounds like poo, as I have heard it
>> was only 11-bit audio). When I'm running:
>> # mplayer -quiet *
>> it plays normally through the usb card even with other processes running,
>> but still doesn't sound near as good as either my ubuntu system or the
>> raspbian image.
>> I also found out that the snd-usb-audio driver indeed does work with all
>> of the channels when I input the command
>> # speaker-test -Dplug:surround51 -c6
>> to test all of the speaker channels. The woman's voice came through on
>> all the appropriate channels, plus they are adjustable in alsamixer. I just
>> can't get mplayer to use them all when using alsa as the backend (I haven't
>> gotten pulseaudio to work in buildroot) and it outputs through the front
>> only. I have the same issue when using alsa as the backend on this card in
>> the raspbian image as well (but good sound) yet it uses the same
>> snd-usb-audio driver, same with my ubuntu system.
>> Would you recommend pulseaudio in my situation?
>> On Wed, Feb 25, 2015 at 1:42 PM, Peter Seiderer <ps.report at gmx.net>
>> wrote:
>>> Hello Lou,
>>> On Tue, Feb 24, 2015 at 05:58:45PM -0600, Lou Crittenden wrote:
>>> > Good news, I found a workaround to the garbled audio issue on use of
>>> > mplayer when using my USB card. What I have to do is pass the -quiet
>>> option
>>> > when running mplayer. For example: mplayer -quiet test.mp3. It turns
>>> out
>>> > that activity on the lcd screen was the culprit, and it interferes
>>> with the
>>> > audio and it ONLY does that when using the usb audio card. When no
>>> options
>>> > are passed, the display continually scrolls the time and whatnot of the
>>> > audio playback every millisecond.
>>> >
>>> > mpg123 has much less terminal activity, and thus doesn't have the
>>> issue.
>>> >
>>> > I was wondering if this is a power issue and if it would work if I
>>> used an
>>> > isolator that allowed the device to receive its own power independent
>>> of
>>> > the Raspberry Pi board? Something like this:
>>> >
>>> >
>>> http://www.ebay.com/itm/ADUM4160-USB-Isolator-Board-ADI-USB-Port-Isolator-Protection-/191303685123?pt=LH_DefaultDomain_0&hash=item2c8a969403
>>> >
>>> > that electronically isolates the usb audio and power from the pi, but
>>> > allows the pi to talk to the device so the sound improves and improves
>>> > power stability.
>>> >
>>> Hard to tell without hearing a sample of what you describe as 'garbled
>>> audio',
>>> but I would less suspect a electrical/decouple problem, more suspect a
>>> pure
>>> resource problem of the mplayer aplication doing audio and display
>>> updates...
>>> Maybe you can stress mplayer -quiet and/or mpg123 doing some concurrent
>>> work/
>>> testbench running (e.g. untar a huge file (kernel source)), etc. and get
>>> the
>>> same audio defects?
>>> I was able to compile and run a rockbox version on RPi/buildroot, but
>>> still
>>> without audio file playing...
>>> Regards,
>>> Peter
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