[mythtv-commits] Ticket #11213: cutting and lossless mpeg2 transcoding generate strange files
MythTV
noreply at mythtv.org
Mon Oct 14 01:22:21 UTC 2013
#11213: cutting and lossless mpeg2 transcoding generate strange files
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Reporter: mythtv@… | Owner:
Type: Bug Report - General | Status: new
Priority: minor | Milestone: unknown
Component: MythTV - Mythtranscode | Version: 0.26-fixes
Severity: medium | Resolution:
Keywords: | Ticket locked: 0
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Comment (by finlay@…):
While manually running some lossless transcodes on US OTA video files
(480i in mpegts) I noticed that even though I was setting the cut points
on keyframes, mythtranscode was reporting that it was converting some B
and P frames to I frames at the cut points. In addition it would report
the need to insert a large number of frames (e.g.1000000+). By varying the
cut frame specification I found that generally by specifying a frame one
greater than the keyframe (as found by myth editing) I could get
mythtranscode runs that would not convert frames. The resulting files
could be analyzed by avconv and report the correct duration and could also
be post-processed by mythffmpeg without a problem. Note this does not
occur for all files that I have tried but does occur for the majority.
My speculation is that:
the myth editing process produces keyframe numbers that are different
than the keyframe numbers that mythtranscode encounters; and,
the mythtranscode conversion of B frames (and possible P frames) to I
frames introduces some error that causes mythffmpeg, vlc and avconv to
fail to correctly analyze the video.
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Ticket URL: <http://code.mythtv.org/trac/ticket/11213#comment:7>
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