[mythtv-users] How to transcode HD recording

[HP-mini]

On Wed, 2014-01-15 at 18:56 +0000, John Pilkington wrote:
> On 15/01/14 18:37, HP-mini wrote:
> > On Sat, 2014-01-11 at 23:30 +0000, John Pilkington wrote:
> >> On 11/01/14 22:24, HP-mini wrote:
> >>> On Sat, 2014-01-11 at 13:07 +0000, John Pilkington wrote:
> >>>> On 11/01/14 12:50, John Pilkington wrote:
> >>>>> On 11/01/14 02:04, HP-mini wrote:
> >>>>>> On Thu, 2014-01-09 at 20:14 +0000, John Pilkington wrote:
> >>>>>>> On 07/01/14 23:29, John Pilkington wrote:
> >>>>>>
> >
> >
> > To clarify:
> > - master (with or without -O FFMPEG=1) fails to find all keyframes
> > (shortlist).
> > - there are no IDR keyframes in any broadcast DVB H264 (AFAIK)
> > - my patched code finds all the keyframes in various international
> > samples.
> >
> > Do you build from source ?
> 
> AFAIK that's the only way of getting 0.27 on el6 clones; so yes, my 
> system was built from git tarball last weekend.  If you're offering, I'd 
> like to see your patches and ought to be able to apply them.  Thanks. 
> But I still hope Jim will come up with something soon :-)
> 

AFAIK The logic around
http://code.mythtv.org/trac/changeset/802e32ba4dc8852da56db170893e95cbc28637e3/mythtv
is odd...
This code change allows any I frame to be treated as keyframe if x
number of frames have processed without finding any..
The code does the opposite of the code patch comment..

AFAIK There are no IDR type keyframes used in broadcast DVB H264.
The IDR causes bitrate spikes.

The H264 parser finds all the real keyframes..for both hd-pvr & normal
broadcast intra-refresh H264..
It always found the IDR frames (if any).

There is a setting for hd-pvr to allow all I frames to be treated as
keyframes. The mpegrecorder sets that variable when using an hd-pvr.

The hd-pvr creates seekable I-frames & IDR keyframes H264 for HD
recordings.

With HD hd-pvr recordings, the decoder can start/seek from all/any I
frames if it has the previous referenced SPS/PPS.

Cutting is a problem using seekable I-frames because you require the
SPS/PPS from a real keyframe to decode.

mkvtoolnix (losscut etc) does not cut on seekable I-frames.

Your recording has a lot of undecode-able data at the start.
Have you tried setting the mythtv-setup option for dvb:
"wait for SEQ start" ?

All H264 & mpeg2video has to start decoding on SEQ or SPS (keyframe).