[mythtv] Ticket #9410: Positioning problems with BBC HD and BBC ONE HD recordings

Paul Gardiner lists at glidos.net
Sun Jan 2 14:36:54 UTC 2011

On 01/01/2011 18:35, MythTV wrote:
> #9410: Positioning problems with BBC HD and BBC ONE HD recordings
> -------------------------------------+-----------------------------
>   Reporter:  mythtv@…                 |          Owner:  janne
>       Type:  Bug Report               |         Status:  assigned
>   Priority:  minor                    |      Milestone:  unknown
> Component:  MythTV - Video Playback  |        Version:  Unspecified
>   Severity:  medium                   |     Resolution:
>   Keywords:                           |  Ticket locked:  0
> -------------------------------------+-----------------------------
> Comment (by jpoet):
>   When trying to detect a "new" access unit (AU), one of the things to look
>   for is a change in the nal_ref_idc value.
>   nal_ref_idc is part of '''every''' NAL UNIT, and we are currently testing
>   to see if it changed for '''every''' NAL UNIT.  Re-reading
>   T-REC-H.264-200711-I!!PDF-E.pdf, I don't think that is correct.  When
>   looking for a "new" AU, the nal_ref_idc should only be tested when the
>   current NAL UNIT is a "slice".
>   I have attached a patch which makes this change.  I have tested it with
>   HD-PVR recordings, and it does not seem to cause anything bad to happen.
>   It would be nice if someone else would read the spec to see if they
>   interpret it the same way.

I've partially tried the patch, in that I've rebuilt mythtv on my
backend with the patch included, and then regenerated positions maps
for some of my recordings using mythcommflag --rebuild. I haven't
rebuilt myth on my frontend yet because I use minimyth, and building
it from scratch can take 10 hours, plus I'll need to remind myself
how to add patches to minimyth. The patch doesn't seem to have fixed
the problem completely, but then again I don't know if you would expect
it to have, or whether it need to be applied to both frontend and

I'm just rebuilding position maps for all my old BBC HD rercordings
to see if the problem looks fixed for any of them.


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