[mythtv-users] Jerky playback on BBC HD Chennels

[HP-mini]

On Mon, 2013-01-28 at 09:15 +1300, HP-mini wrote:
> On Sun, 2013-01-27 at 17:25 +0000, Fred Watt wrote:
> > On 27/01/13 16:51, Tim Draper wrote:
> > 
> > > 
> > > 
> > > On 25 January 2013 06:52, Fred Watt <fredwattmythtv at gmail.com>
> > > wrote:
> > >         On 24/01/13 21:03, Tim Draper wrote:
> > >         
> > >         > Are there any plans to revert this in 0.26-fixes? i too am
> > >         > suffering with BBC HD recordings since a recent update.
> > >         Me too - awful.  Massive regression.
> 
> > > I've just been looking at this to see if theres been any updates -
> > > none yet.
> > > for reference of the bug - http://code.mythtv.org/trac/ticket/11356
> > > 
> > > re-reading through thread and the bug tracker info, it's down to
> > > ffmpeg.... since i tend to update my entire system rather than just
> > > mythtv, is this something mythtv can help out with, or are we
> > > waiting on a fix from the ffmpeg devs to fix this annoyance??
> > > atleast the 'work around' is to ammend the recording rules for BBC
> > > One HD shows, and rely on BBC One (SD) for the recordings.
> > > Interestingly people are reporting it on just one channel; BBC HD,
> > > i'm having issues on BBC One HD and ITV HD aswell! (C4 HD doesn't
> > > exhibit the issue)
> > > 
> 
> > Yes we're stumped as well.... nearly all of our viewing is now BBC HD,
> > and over the last two weeks we're unable to watching anything easily.
> > What does seem to work is 'livetv', I watched the tennis today in HD
> > and it started out stuttery but after 30 seconds was completely
> > watchable.  The recordings on the other hand are frame jerky.  I
> > wonder why that is?
> > 
> > Correct me if I am wrong, but my understanding is that ffmpeg is
> > statically linked.  So it does not matter which version is installed
> > on our ubuntu boxes.  Like you, these days I use the repositories, so
> > we need for a fixed version.
> > 
> > Very frustrating.  I can watch using another player but it's all a
> > faf... as I prefer using mythfrontend.
> > _______________________________________________
> 
> If livetv works then the seektable generation must be different between
> recording & watching live. Or is it the recording start?
> 
> Can you watch these recordings from "videos" ?
> Seektables are optional for "videos", none of mine seek correctly
> without generating them. But your recordings might play smooth(er)
> without.
> 
> FWIW MythTV does make a mess of the beginning of recordings..(There is a
> ticket/patch/commit that improves this). This causes problems with
> transcoding & cut frame accuracy.
> 
> You could try:
> - find (with ffprobe) first "coded picture number" byte offset & cut off
> file beginning with "dd".
> - rebuild seektable with mythtranscode or mythcommflag (or mythutils).
> - write a script with "ffprobe" & generate the right seektable offsets. 
> 
> Can you easily upload (somewhere) a 1 minute recording ?
> (could cut end off with "dd" but I do need the start untouched)
> 
> For me, Ticket #11159 caused jerky/judder on recording discontinuities
> (cut files) on SD channels.
> 
> I find it is possible to induce this judder/jerky playback on any H264
> recording by messing around in the cutlist editor at the start.
> 
> Brett.

Further to locked ticket 11159:
There is a sample HDPVR recording file mentioned in the ffmpeg trac..

If you cut 6023 packets (1132324 bytes) off the start of the sample
hdpvr file JYA "11159 HD-PVR sample.mpg"..the file plays correctly in
myth 0.26+fixes without requiring this revert patch.

Like I said before..you can induce this playback effect, in any of my
h264 files, by tooling around with cutlist editor in frame & keyframe
index at start..