[mythtv-users] Shuttle SK41G sound problem
Joseph A. Caputo
jcaputo1 at comcast.net
Mon Dec 22 10:55:31 EST 2003
On Sunday 21 December 2003 23:15, Steven Marcotte wrote:
> On Sun, 2003-12-21 at 07:42, Joseph A. Caputo wrote:
> > > OK, if I open xawtv and enter the command 'aplay /dev/dsp' and
> > > adjust the levels in aumix as follows:
> > >
> > > Volume: 70
> > > PCM: 70
> > > CD: 100
> > > IGain: 100
> > >
> > > The volume level is fine, there is no distortion, and there are
> > > two audio tracks. If I set the CD input to 0, one audio track
> > > goes away and I am left with on audio track slightly out of sync.
> > >
> > > If I quit aplay, aumix, and xawtv and start MythTV with the same
> > > levels, I get the same result, loud and distorted. I can adjust
> > > the audio levels down, and the volume will get lower, but the
> > > distortion remains. In fact if I set the levels in aumix as
> > > follows, the sound is very quiet but still distorted.
> >
> > What do you mean 'the same levels'? Depending on your settings,
> > mythfrontend may adjust your audio output levels on startup.
>
> What I mean is, prior to starting mythfrontend, the levels are set in
> aumix the same as the xawtv/aplay experiment, VOL=70, PCM=70,
> IGain=100. Once I start watching live TV, mythfrontend sets the
> levels according to my MythTV preferences, VOL=40, PCM=40, IGain=100.
> Sorry I didn't make that too clear.
>
> > > Volume: 20
> > > PCM: 20
> > > CD: 0
> > > IGain: 2
> >
> > PCM & IGain are most likely to affect distortion.
> >
> > > I can play music from Myth Music with the same levels as the
> > > xawtv experiment, and it plays fine.
> > >
> > > ALSA registers two DSP devices for my via82xx sound card,
> > > /dev/dsp and /dev/adsp. I reran the xawtv experiment with for
> > > /dev/adsp, with the following levels:
> > >
> > > Volume: 70
> > > PCM: 70
> > > CD: 100
> > > IGain: 100
> > >
> > > The output is loud and distorted, there is too much distortion to
> > > tell if there is two audio tracks. If I set the IGain level to 0
> > > the distortion goes away and you get a normal sound output in
> > > real-time from the CD channel.
> > >
> > > I thought this is great, finally I'm able to reproduce the
> > > problem outside of MythTV. The first thing I did was double
> > > check to make sure that neither the Myth front-end or back-end
> > > was configured to use /dev/adsp. But as luck would have it,
> > > MythTV was configured to use /dev/dsp for capture and playback;
> > > lsof verified that this was the case.
> > >
> > > The via82xx chipset is suppose to support full-duplex mode. I
> > > have run the gamut of related module parameters with no success.
> > > But shouldn't a TV recording be fine regardless of weather or not
> > > my soundcard supports full-duplex? lsof reports that the only
> > > process accessing /dev/dsp is the MythTV back-end, and that is in
> > > read-only mode.
> >
> > Is this while watching LiveTV? If so, mythfrontend should also
> > have /dev/dsp open; if it doesn't, then are you sure* that
> > mythfrontend is configured to use /dev/dsp for TV playback? There
> > are 2 places in the frontend setup where this is configured -- 1
> > for mythmusic & one for TV playback. When changing settings you
> > must continue through all the screens until the end, or the changes
> > do not get applied. Based on your observations above, it sure
> > sounds like mythfrontend is playing through /dev/adsp.
>
> Sorry if I wasn't clear. When I am watching live tv, lsof shows that
> mythbackend is reading from /dev/dsp and mythfrontend is writing to
> /dev/dsp. No other processes are accessing /dev/dsp or /dev/adsp.
>
> # lsof | grep dsp
> mythbacke 377 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 409 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 410 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 411 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 412 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 413 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 414 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 415 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 416 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 417 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 418 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythfront 426 mythtv 15w CHR 14,3 144369 /dev/dsp0
> mythfront 440 mythtv 15w CHR 14,3 144369 /dev/dsp0
> mythfront 473 mythtv 15w CHR 14,3 144369 /dev/dsp0
> mythbacke 474 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 475 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 476 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 477 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythbacke 478 mythtv 22r CHR 14,3 144369 /dev/dsp0
> mythfront 479 mythtv 15w CHR 14,3 144369 /dev/dsp0
> mythfront 480 mythtv 15w CHR 14,3 144369 /dev/dsp0
> mythfront 481 mythtv 15w CHR 14,3 144369 /dev/dsp0
> mythfront 482 mythtv 15w CHR 14,3 144369 /dev/dsp0
>
> When I am just recording a show, lsof shows that mythbackend is the
> only process reading from /dev/dsp.
>
> # lsof | grep dsp
> mythbacke 377 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 409 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 410 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 411 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 412 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 413 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 414 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 415 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 416 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 417 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 418 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 497 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 498 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 499 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 500 mythtv 18r CHR 14,3 144369 /dev/dsp0
> mythbacke 501 mythtv 18r CHR 14,3 144369 /dev/dsp0
>
> There are no other processes reading or writing to either /dev/dsp or
> /dev/adsp. I verified that the recording is bad by transcoding it
> and playing it on another computer.
>
> Just to triple check the settings, I dumped the database and
> everything is in fact configured to use /dev/dsp.
>
> I don't know why this is so difficult. Everything seems to be
> configured correctly, but it still sounds like I have a blown speaker
> (even though I don't). :|
>
> Quattro
The only other thing I can think of is maybe it doesn't like the sample
rate you have configured in Myth. Didn't you say you were using 32kHz
at one point? Try different sample rates. Beyond that, I'm stumped.
Maybe it's the output level of your TV card, but I didn't think Myth
changed that...
Anyone else want to chime in? It sounds like he's done everything
right.
-JAC
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