[mythtv-commits] Ticket #12010: mythcommflag --rebuild does not re-create good seektables with h264 recordings

[MythTV]

#12010: mythcommflag --rebuild does not re-create good seektables with h264
recordings
-----------------------------------------+----------------------------
 Reporter:  J.Pilk@…                     |          Owner:  stichnot
     Type:  Bug Report - General         |         Status:  accepted
 Priority:  minor                        |      Milestone:  unknown
Component:  MythTV - Video Decoding      |        Version:  0.27-fixes
 Severity:  medium                       |     Resolution:
 Keywords:  mythcommflag --rebuild h264  |  Ticket locked:  0
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Changes (by stichnot):

 * owner:   => stichnot
 * status:  new => accepted
 * component:  MythTV - General => MythTV - Video Decoding


Comment:

 The situation here is that the recorder has captured keyframes as a
 combination of IDR keyframes and non-IDR I-frames, but mythcommflag is
 only registering IDR keyframes.

 The fundamental problem is that the particular recorder decides whether
 non-IDR I-frames are allowed to act as keyframes, but the recorder leaves
 no clues in the recording itself  about which recorder was used.  This
 leaves mythcommflag to guess whether or not to register a keyframe when it
 sees a non-IDR I-frame.

 The default behavior is to assume only IDR keyframes, but then you find
 e.g. DVB-S transmissions that completely lack IDR keyframes, hence the
 logic in 802e32ba4dc8852da56db170893e95cbc28637e3 that rewinds and retries
 with the more lenient setting when it doesn't find an IDR keyframe within
 the first 1000 or so frames.

 Unless ffmpeg can somehow figure this out for us automatically, the only
 solution I can think of is to add an extra flag to "mythcommflag
 --rebuild" that allows the user to manually override the IDR-vs-I-frame
 decision.

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Ticket URL: <http://code.mythtv.org/trac/ticket/12010#comment:2>
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