[mythtv-users] unusual behavior of transcoded mpeg-4 recordings

David Murphy dm1000 at gmail.com
Thu Mar 15 22:42:43 UTC 2007

I did a bit of searching but didn't come up w/ a description that neatly 
matched this symptom.

I've been transcoding HD and SD programs captured by my air2pc card. 
The programs transcode fine and look great when played back.  I can skip 
and jump forward or back to my hearts content and the playback will 
resume normally.  However, if I pause, fast forward or rewind at any 
speed, playback will not resume properly.  For example, if I pause a 
transcoded program and then resume playback the video appears to play at 
~1/2 speed or perhaps it would be more accurate to say that it appears 
to play at 1/2 normal framerate although the audio remains synced. If I 
were then to press Fast Forward to 3x speed the video smooths out and 
plays at normal framerate except of course there is no audio.

I haven't changed any of the compression settings that had warnings 
attached to them.  For example, here is a profile that seems to generate 
the problem:

-lossless transcoding: NO
-resize video while transcoding: YES
-width: 480  height: 480
-codec: mpeg-4
-bitrate: 2200
-max quality: 2
-min quality: 15
-max quality difference between frames: 3
-scale bitrate for frame size: NO
-enable high-quality encoding: YES
-enable 4MV encoding: YES
-enable interlaced DCT encoding: NO
-enable interlaced motion estimation: NO
codec: mp3
sampling rate: 32000
mp3 quality: 5
volume: 90

This is a Mythdora 3.2 system.  I'm not sure why playback would be 
normal after a skip or jump but not after a pause.  Am I using one or 
more problematic transcoder settings?

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