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

[Richard]

On 19/01/13 03:25, Neil Salstrom wrote:
>
> Richard,
>
> Here is a playback log using openGL.
>
> http://pastebin.com/1rSv9dzP
>
> I was contacted by someone off list who said he's been experiencing
> the same problems I've seen.  He did not mention the movie titles but
> it's an issue that has cropped up recently.
>
> The problem was seen with both VDPAU and OpenGL.  I had 'top' going in

Ok, so it doesn't appear to have anything to do with any special 
handling required for the presentation method.

> a terminal window on my laptop as it was playing on my HTPC.  CPU
> never went above ~30% using OpenGL and ~10% with VDPAU.  When it
> happens I do not see any blocking in the picture or something similar
> to pixilation.  What I see are brief pauses ever second or so.  The
> picture is very juddery and audio drops out during the judder.  The
> picture remains clear but it looks like it drops a pile of frames.
> There can be times where the movie goes several minutes without
> problem then it starts up for several minutes of judder.

I get something similar on Cars 2 but it only lasts for a couple of 
seconds.  The audio plays fine but the picture freezes.  That was what I 
tracked down to a discontinuity in the audio timestamp.  The video 
timestamp seems to do the same soon after but maybe it doesn't on your 
DVD.  Or it's an entirely different problem, which is quite possible.

> What I am curious about is:
>
> 2013-01-18 17:27:17.976224 I  Trying to match best refresh rate 29.970Hz
> 2013-01-18 17:27:17.976279 I  Trying 1920x1080 59.939 Hz
> 2013-01-18 17:27:18.030063 I  Dynamic TwinView rate found, set
> 59.9394Hz as XRandR 54
> 2013-01-18 17:27:18.175301 I  SwitchToVideo: Video size 720 x 480:
>      Switched to displaying resolution 1920 x 1080, 487mm x 274mm
>
> Ok, so is this upconverting to 1080p?  The DVD is 29.970Hz then it's
> doubling the frame rate to 59.939Hz and going from 480p to 1080p?

Yes.

> Once it starts playing and the judder starts we see this:
>
> 2013-01-18 17:28:24.160577 D  DVDRB: DVDNAV_NAV_PACKET
> 2013-01-18 17:28:24.233484 I  Player(0): FPS:   24.18 Mean: 41354
> Std.Dev:  9959 CPUs: 20% 19% 18%
> 2013-01-18 17:28:24.802166 D  DVDRB: DVDNAV_NAV_PACKET
> 2013-01-18 17:28:25.451091 I  Player(0): Waiting for video buffers...
> 2013-01-18 17:28:25.486048 D  DVDRB: DVDNAV_NAV_PACKET
> 2013-01-18 17:28:25.521649 I  Player(0): Waiting for video buffers...
> 2013-01-18 17:28:25.577362 I  Player(0): Waiting for video buffers...
> 2013-01-18 17:28:25.683569 I  Player(0): Waiting for video buffers...
> 2013-01-18 17:28:25.822837 I  Player(0): Waiting for video buffers...
>
> Why is it playing at 24.18 FPS when before it was reported at 29.970 FPS?

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.

> There are lots of "Waiting for video buffers".  No idea what is going on!

That's what we to eliminate but I'm not sure what's causing it either.

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.

It's tricky trying to pin these things down.  I've spent several very 
long evenings constantly trying out different logging options and adding 
additional logs to track down the cause of a single issue.  A friend of 
mine has Inception on DVD but I'm almost certain it isn't region 1.  The 
differences could well be sufficient that I wouldn't get the same 
playback issues.  Wouldn't hurt to try but I won't be able to get it 
until next week, so let's see if we can figure anything out from your 
side first.

Richard.