[mythtv-commits] Ticket #11435: recordedseek as recorded differs from mythcommflag

MythTV noreply at mythtv.org
Thu Jul 4 08:46:26 UTC 2013


#11435: recordedseek as recorded differs from mythcommflag
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 Reporter:  blm-ubunet@…          |          Owner:  jpoet
     Type:  Bug Report - General  |         Status:  closed
 Priority:  minor                 |      Milestone:  0.27
Component:  MythTV - Recording    |        Version:  Master Head
 Severity:  low                   |     Resolution:  fixed
 Keywords:  H264 recordedseek     |  Ticket locked:  0
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Comment (by blm_ubunet@…):

 My patch(s) also fixed the buffer offset problem in dtvrecorder.cpp.

 HD-PVR:
 H264Parser.cpp correctly identifies actual IDR frames for HD-PVR & my
 later patch accidentally disabled the "all I frames as keyframes"
 override.

 The identified IDR frames match with ffprobe & avidemux.
 I have also used Elecard StreamEye (demo) analyser to inspect streams.

 The original HD-PVR f/w produced non-compliant streams described as "No
 IDR, seekable I frame with no SEI recovery point messages.
 The "use_I_forKeyframes" function call (from mpegrecorder.cpp) sets
 "I_is_keyframe=true" for HD-PVR recordings. This then causes all I frames
 to be identified keyframes.
 I imagine this hack was needed to support the original HD-PVR streams.

 The HD-PVR recording samples I have, use AVC main at L4.0 for 720p60 with an
 I frame every 28 frames with every 4th I frame as IDR. For IDR nal, the
 SEI recovery count is set correct (==0) & exact_match==1.

 So for correct keyframe detection (in HD-PVR) needs I_is_keyframe=false.
 The non-IDR I frames do seem to be seekable so perhaps the I frames
 positions also need to be stored into the seektable ( but not as
 keyframes).

 This keyframe error would explain the 0 to 2 sec position errors that have
 plagued the "lossless_cut" script.

 Thanks.

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Ticket URL: <http://code.mythtv.org/trac/ticket/11435#comment:43>
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