[mythtv-users] Strange Audio Problem 0.25

[Igor Cicimov]

On Wed, Jun 13, 2012 at 3:40 AM, jr <jraymyth at gmail.com> wrote:

> I have a fresh install of Ubuntu 12.04 and MythBuntu 0.25 FE/BE.  The
> install went without a hitch.  The tuners and channels are all
> configured.  Blah blah blah.  The problem I am having is with the
> audio.
>
> I went through the Setup Wizard and set the audio device
> (ALSA:hdmi:CARD=NVidia,DEV=1).  The speaker test hissed as expected.
> Video Playback Profile is set to VDPAU High Quality. Test High
> Definition plays me a nice movie intro of someone walking across icy
> mountains.  The incidental music is clear and audible.
>
> So I went to make a recording and played it.  The video was clear, but
> no audio was emitted.  The recording does have sound when played
> through VLC.  I figure that its a config problem, but of what?  ALSA
> is clearly working with the HDMI port.  MythTV is communicating with
> ALSA, in the setup at the least.  I don't mind digging in...but where
> do I dig?
>
> Thanks,
> jr
>
> Intel DQ67EP (i5) -- Onboard audio is disabled in the bios
> MSI N210-MD512H GeForce 210 512MB
> 4GB
>
>
> mythuser at Jotun:~$ aplay -l
> **** List of PLAYBACK Hardware Devices ****
> card 0: PCH [HDA Intel PCH], device 0: ALC888 Analog [ALC888 Analog]
>  Subdevices: 1/1
>  Subdevice #0: subdevice #0
> card 0: PCH [HDA Intel PCH], device 1: ALC888 Digital [ALC888 Digital]
>  Subdevices: 1/1
>  Subdevice #0: subdevice #0
> card 1: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0]
>  Subdevices: 1/1
>  Subdevice #0: subdevice #0
> card 1: NVidia [HDA NVidia], device 7: HDMI 0 [HDMI 0]
>  Subdevices: 1/1
>  Subdevice #0: subdevice #0
> card 1: NVidia [HDA NVidia], device 8: HDMI 0 [HDMI 0]
>  Subdevices: 1/1
>  Subdevice #0: subdevice #0
> card 1: NVidia [HDA NVidia], device 9: HDMI 0 [HDMI 0]
>  Subdevices: 1/1
>  Subdevice #0: subdevice #0
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>


"2012-06-12 19:58:11.009507 E  ALSA: Error opening
/proc/asound/card1/pcm7p/sub0/prealloc: Permission denied.
2012-06-12 19:58:11.009521 E  ALSA: Try to manually increase audio
buffer with: echo 128 | sudo tee
/proc/asound/card1/pcm7p/sub0/prealloc
2012-06-12 19:58:11.009535 E  ALSA: Unable to sufficiently increase
ALSA hardware buffer size - underruns are likely
2012-06-12 19:58:11.009543 I  ALSA: OpenDevice
hdmi:CARD=NVidia,DEV=1,AES0=6,AES1=0x82,AES2=0x00,AES3=0x01 for
passthrough"

You might also check the user permissions on /dev/asound directory and if
the user you are running MythTV with belongs to video and audio groups. I'm
not an expert in Myth audio but looks like it tries to open the device 7 on
the Nvidia card for playback?

You might also try to increase the buffer size manually as the error
suggests. Run

$ echo 4096 > /proc/asound/card1/pcm7p/sub0/prealloc

and see what happens. If the command fails with permissions issue then you
really have a problem with your Myth user editing the ALSA files. Fix the
permissions or run the command as root and start the playback again to see
if things have improved.

Igor
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