[mythtv] Frame accurate MPEG2 commercial cutting

Chris Pinkham cpinkham at bc2va.org
Fri Jan 13 05:38:32 UTC 2006

> mythtranscode (that I'm aware of), it turns out that myth just doesn't
> count frames in exactly the same way.  In addition, the way the index
> is generated in myth isn't very reliable (a cutpoint will happen at a
> different point depending on whether you watch the video from the
> beginning or whether you use fast-forward/rewind), and myth's
> different ways of storing them (the dvbrecorder and ivtv recorders
> don't use exactly the same algorithm to generate the index, and using
> mythcommflag to rebuild the index results in yet another answer).  the
> above only applies to MPEG2 as far as I can tell.

This has been mentioned before and has caused issues with commercial
flagging in the past.  It would be nice to get these (more) standardized
after 0.19.  mythcommflag doesn't actually rebuild the positionmap, it
just plays through the video and if there wasn't a positionmap initially,
mythcommflag tells the decoder to save the positionmap that was generated
while decoding the video.

> For the time being, the following solutions may work:
> 1) regenerate the key-frame index using 'mythtranscode -b' before
> selecting cut points

Did you find that this differed from the positionmap the decoder generated
if you run "mythcommflag --rebuild"


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