[mythtv-users] Recent DVD problems with video and audio drops

Neil Salstrom salstrom at gmail.com
Sun Jan 20 23:30:24 UTC 2013


On Sat, Jan 19, 2013 at 4:48 AM, Richard <peper03 at yahoo.com> wrote:

> A DVD can either be 29.97 or 25 fps depending on whether it's NTSC or PAL.
> If it's an NTSC disc and should be played at 24fps (or 23.96 or whatever the
> actual value is) it performs a pull-down.  To be honest, I have very little
> experience with this and nearly all my DVDs are PAL.
> I just tried one of the region 1 DVDs I have and that reported ~23.97fps
> too.  Also there are chunks of your logs where there is apparently no
> playback problem and it's still reporting around the same frame rate.
>
> The frame rate shown is more the actual framerate rather than the intended
> framerate, which is why it sometimes jumps around a bit when you get
> playback issues.

Ahh...  I think I'm beginning to understand.  Sorry for the beginner
questions from me.  The original film was 24fps (well, 23.96).  The
movie on the disk is 29.97fsp but pulldown occurs to bring it back to
the native 23.96?  Is this being done via a VDPAU deinterlace
function?

>
> Could you try again with -v playback,timestamp --loglevel=debug? That'll
> spew out an awful lot of messages but may help identify timing issues.  It's
> probably not necessary to post the entire log (it's possible you hit
> pastebin's limits) but a section starting before the playback issues occur
> would be good.

I had a brief moment of inspiration and decided to start mythtv via a
terminal window on my laptop.  I did "export DISPLAY=:0" then I was
able to start mythtv on my HTPC and watch the resulting log messages
as they occurred.  I've been watching after starting the frontend with
-v playback,timestamp --loglevel=debug but that puts out a HUGE amount
of data.  I've managed to pause right after a series of judders but I
can't make much of the logs.

There is audio dropout as well during these stutters.  My receiver
gives a little click when an audio source is cut off or changed and I
get a rapid series of clicks when this happens.

One thing I do see occasionally is:

2013-01-20 15:12:41.739847 I  VidOutVDPAU: Frame E is in use by avlib
and so is being held for later discarding.
2013-01-20 15:12:41.776279 I  VidOutVDPAU: Frame E is in use by avlib
and so is being held for later discarding.
2013-01-20 15:12:41.812685 I  VidOutVDPAU: Frame E is in use by avlib
and so is being held for later discarding.

Here is a pastebin of a log that encompasses several seconds where the
dropouts occurred:

http://pastebin.com/hZPq8fhe

I also ran it without timestamp but with playback,audio.  I see a lot of this:

2013-01-20 15:23:31.949383 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:32.010041 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:32.018994 I  ALSA: WriteAudio: buffer underrun
2013-01-20 15:23:32.102758 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:32.221823 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:32.257906 I  ALSA: WriteAudio: buffer underrun
2013-01-20 15:23:32.341658 D  DVDRB: DVDNAV_NAV_PACKET
2013-01-20 15:23:32.736604 D  DVDRB: DVDNAV_NAV_PACKET
2013-01-20 15:23:33.142852 I  Player(0): FPS:   20.89 Mean: 47872
Std.Dev: 18452 CPUs: 100% 100% 312%
2013-01-20 15:23:33.376318 D  DVDRB: DVDNAV_NAV_PACKET
2013-01-20 15:23:33.976712 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:34.016253 D  DVDRB: DVDNAV_NAV_PACKET
2013-01-20 15:23:34.061232 I  ALSA: WriteAudio: buffer underrun
2013-01-20 15:23:34.065159 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:34.134498 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:34.260119 I  ALSA: WriteAudio: buffer underrun
2013-01-20 15:23:34.346417 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:34.419615 I  ALSA: WriteAudio: buffer underrun
2013-01-20 15:23:34.429152 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:34.494282 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:34.632919 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:34.693593 I  Player(0): Waiting for video buffers...
2013-01-20 15:23:34.737113 D  DVDRB: DVDNAV_NAV_PACKET
2013-01-20 15:23:34.739825 I  ALSA: WriteAudio: buffer underrun

Are the alsa buffer underruns involved?  If this is the case, why does
it only happen with the DVD and not a mkv which has the exact same
audio and video?

Thanks!


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