[mythtv] Air2PC / DVB audio playback fails in Mythtv - AC3 handling problem?

Blammo [doh] blammo.doh at gmail.com
Mon Feb 14 22:56:01 UTC 2005


Interestingly, mine seems to be having a little trouble as well.

As way of history, I intended to use XvMC, but I can't, because of the
"Prebuffering" issue, which eats CVS myth for lunch.

Frontend1 is a Mobile Barton 2400, 200mhz FSB, 1800mhz clock, PC3200,
NV 5200ultra AGP, FC3 2.6.10-DVB kernel. Currently using 960x540p
output.

Frontend is currently set for deinterlace, BOB, using Libmpeg2.

I have (3) HD recordings on my backend right now, and here's how they play.

2092 - NBC, Tonight Show, 1920x1080x29fps - plays smooth, loses audio
or locks if you skip ahead or behind. Plays beginning to end just fine
if you let it.
VIDEO:  MPEG2  1920x1080  (aspect 3)  29.970 fps  18906.0 kbps (2363.2 kbyte/s)

2094 - ABC, Boston Legal, 1280x720x59fps - choppy chunky CPU can't keep up.
VIDEO:  MPEG2  1280x720  (aspect 3)  59.940 fps  45000.0 kbps (5625.0 kbyte/s)

2081 - CBS, CSI, 1920x1080x29fps - plays fine, CPU at 99% however.
VIDEO:  MPEG2  1920x1080  (aspect 3)  29.970 fps  45000.0 kbps (5625.0 kbyte/s)

looking at this, I think it's just CPU.

I have some room to clock the CPU up.. I've had it undervolted and
underclocked to try to keep the heat and noise down, but I may not
have any choice.


> Dohh I was a little bit late. Must be my processor not keeping up then.
> 
> On Tuesday 15 February 2005 08:09, Blammo [doh] wrote:
> > Ok, ran home for lunch.
> >
> > AC-3 Passthrough off - I have WORKING audio on the analog ports. Myth plays
> > the AC-3 Passthrough on, change to /dev/dsp - I have audio via SPDIF on my
> > amp.
> >
> >
> > So the problem was trying to push digital out an analog port, which
> > isn't myth's fault, but mine. And I'm not even sure myth could be made
> > aware it was failing..
> >
> > Now if we could just get XvMC and Myth 0.17 happy, almost all my
> > problems would be gone... for now.
> >
> > Thanks all for your help. Consider this issue closed.
> >
> > On Mon, 14 Feb 2005 11:22:48 -0700, Blammo [doh] <blammo.doh at gmail.com>
> wrote:
> > > That's odd.
> > >
> > > ahhh.. wait.. I think I got it... can't test this yet, but I have a
> > > theory:
> > >
> > > MythTV is set up for output to /dev/adsp, which is the ANALOG outputs
> > > of my sound card, IE directly to the TV. MythVideo is setup up for
> > > /dev/dsp, which is the DIGITAL outputs of my sound card. In the past,
> > > this has made complete sense, since no TV was digital, and all movies
> > > were.
> > >
> > > However, in this case, you can't send AC-3 out an analog port. so that
> > > may be why we're hearing the chiff-chiff.
> > >
> > > Which now brings up several question:
> > >
> > > If I turn off AC-3 passthrough, will it play back correctly, IE convert
> > > it? Is there any way to choose a different output device, only for AC-3?
> > > IE, use /dev/adsp for normal output, use /dev/dsp for AC-3.
> > >
> > > It's somewhat important, at least in my case, to keep the MythTV audio
> > > going out the analogs, in that it gives volume control to Myth. As
> > > soon as I sent the audio out the digital, I lose volume control. I've
> > > played with all the mixer settings, and nothing seems to affect that.
> > > Other people use the frontend way more than I do, they have a hard
> > > time working multiple remotes.
> > >
> > > Thoughts?
> > >
> > > Thanks Isaac for your help with this. I hope it turns out being this
> > > easy..
> > >
> > > On Mon, 14 Feb 2005 12:45:51 -0500, Isaac Richards <ijr at case.edu> wrote:
> > > > On Monday 14 February 2005 11:38 am, Blammo [doh] wrote:
> > > > > Small is somewhat of a misnomer when it comes to DVB files, but here
> > > > > is a short clip. I was on live, hit record, waited a few seconds, and
> > > > > stopped the recording:
> > > > >
> > > > > http://216.27.229.222/tmp/air2pc.sample.nuv.gz
> > > > >
> > > > > Apologies, it is 30M, even GZ'd.
> > > >
> > > > Plays fine here in myth.
> > > >
> > > > Isaac
> > > > _______________________________________________
> > > > mythtv-dev mailing list
> > > > mythtv-dev at mythtv.org
> > > > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-dev
>


More information about the mythtv-dev mailing list