[mythtv-users] HD 720p Audio/Video sync problem - some times

[Douglas Wagner]

On Dec 11, 2007 11:06 AM, MythTV <mythtv at blandford.net> wrote:

> DaveD wrote:
> > I am having trouble with A/V sync on some HD shows recorded from our PBS
> > channel.  It is the only channel I get that broadcasts 720p.  Some shows
> > have the problem, some do not.  What happens is the video continuously
> > races ahead of the sound and Myth constantly adjusts, some times slowing
> > the video, some times speeding up (and dropping parts of) the sound.
> > It's very unwatchable.
> >
> > Good news is I can watch the recordings with Xine or Mplayer.  Both work
> > fine.  Myth works fine on all other HD recordings (all other HD channels
> > are 1080i).  All SD works fine.
> >
>
> I posted yesterday about a similar problem I am having as well.
>
> I recorded a show last night that would exhibit the problem.
>
> It is a SD Digital show.
>
> Mplayer can play it without any problem ( 7% cpu ) but mythtv stutters
> continuously and is unwatchable.
>
> I tried all of the predefined playback profiles and non of them made any
> difference.
>
>
> Mythtv:
> 2007-12-11 10:04:53.104 NVP: Video is 30 frames ahead of audio,
>                        doubling video frame interval to slow down.
> 2007-12-11 10:04:53.170 NVP: Video is 30 frames ahead of audio,
>                        doubling video frame interval to slow down.
> 2007-12-11 10:04:53.171 NVP: Video is 30 frames behind audio (too slow),
> droppin
> g frame to catch up.
> 2007-12-11 10:04:53.171 NVP: Video is 30 frames behind audio (too slow),
> droppin
> g frame to catch up.
> 2007-12-11 10:04:53.171 NVP: Video is 30 frames behind audio (too slow),
> droppin
> g frame to catch up.
> 2007-12-11 10:04:53.171 NVP: Video is 30 frames behind audio (too slow),
> droppin
> g frame to catch up.
> 2007-12-11 10:04:53.171 NVP: Video is 30 frames behind audio (too slow),
> droppin
> g frame to catch up.
> 2007-12-11 10:04:53.171 NVP: Video is 30 frames behind audio (too slow),
> droppin
> g frame to catch up.
> 2007-12-11 10:04:53.254 NVP: Video is 30 frames ahead of audio,
>                        doubling video frame interval to slow down.
> 2007-12-11 10:04:53.297 NVP: Changing speed to 0
>
> Mplayer:
> TS file format detected.
> VIDEO MPEG2(pid=99) AUDIO A52(pid=100) NO SUBS (yet)!  PROGRAM N. 1
> VIDEO:  MPEG2  528x480  (aspect 2)  29.970 fps  15000.0 kbps (1875.0
> kbyte/s)
> [VO_XV] Could not grab port 355.
> ==========================================================================
> Opening video decoder: [mpegpes] MPEG 1/2 Video passthrough
> VDec: vo config request - 528 x 480 (preferred colorspace: Mpeg PES)
> Could not find matching colorspace - retrying with -vf scale...
> Opening video filter: [scale]
> The selected video_out device is incompatible with this codec.
> Try appending the scale filter to your filter list,
> e.g. -vf spp,scale instead of -vf spp.
> VDecoder init failed :(
> Opening video decoder: [libmpeg2] MPEG 1/2 Video decoder libmpeg2-v0.4.0b
> Selected video codec: [mpeg12] vfm: libmpeg2 (MPEG-1 or 2 (libmpeg2))
> ==========================================================================
> ==========================================================================
> Opening audio decoder: [liba52] AC3 decoding with liba52
> Using SSE optimized IMDCT transform
> Using MMX optimized resampler
> AUDIO: 48000 Hz, 2 ch, s16le, 192.0 kbit/12.50% (ratio: 24000->192000)
> Selected audio codec: [a52] afm: liba52 (AC3-liba52)
> ==========================================================================
> AO: [alsa] 48000Hz 2ch s16le (2 bytes per sample)
> Starting playback...
> VDec: vo config request - 528 x 480 (preferred colorspace: Planar YV12)
> VDec: using Planar YV12 as output csp (no 0)
> Movie-Aspect is 1.33:1 - prescaling to correct movie aspect.
> VO: [xv] 528x480 => 640x480 Planar YV12
>
>
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>


I hate to be the one to mention this, but unfortunately I had that issue for
about a year before I upgraded the box.  Like clockwork, anything recorded
off our local ABC Affiliate here in St. Louis would have it's audio out of
sync with it's video through Myth while I could drop out of Myth and play it
through Xine without any issues at all.

As a matter of fact it happened to me no more than 2 weeks ago for the first
time in ages.  I was getting random Linux Lockups while playing back video
(The whole machine would freeze and die, SSH unresponsive, console switches
(from text to graphical or among text consoles) didn't work, etc.) and I had
fiddled with some of the settings (BTW I feel like I've traced this to
OpenGL in 20.2...I was using Open GL for 3 - 4 months in 20.1 and had NO
issues with lockup, but I believe that's the only setting I've disabled on
my system atm) including the XvMC settings.

But anyway, to get back on track with the thread: In essence A/V sync wasn't
working, I'd drop out of Myth and load up Xine and everything would work
perfectly fine.  That was my solution for 6 - 8 months when I first started
using the system.