[mythtv-users] Lossless cut error - last video segment not included in resulting video file
r.d.vaughan at rogers.com
Thu Nov 1 20:41:57 UTC 2012
1) With h.264 video encodings I remember reading that Avidemux v2.5x
tended to cut to the keyframe earlier than what was marked in the GUI.
Not sure what that meant but I occasionally had to adjust acut where the
end point caught a bit of a commercial.
2) With mkvmerge "deciding" on which keyframe to cut, the translation
from a MythTV seek table keyframe to a mkvmerge time code is not
exact.Lossless Cut calculates to the full ninedecimal digits
(nanosecond) that mkvmerge can accept. Even at that their may be times
where mkvmerge is using a keyframe not in-sync with what MythTV had
determined to be a keyframe.I further speculate that the reason that
ffmpeg show significantly more video artefacts at cut points is because
it will only accept six digits of time code decimal accuracy so its
selection of a keyframe show even more variation.
What would be best is if Avidemux 3.0, ffmpeg and mkvmerge all accepted
keyframes numbers as cut points along with time codes. Although the
stable version of Avidemux 2.5x still uses keyframe numbers it cannot
edit HDPVR h264 1080i recordings and seems to have video file size
limits. The next releaseof Avidemux 3.0 is resolving those issuesbut has
switched totime code cut points.
More grist for the grist mill.
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