[mythtv-users] Keyframe identification in cutlist editor

John Pilkington J.Pilk at tesco.net
Tue Feb 21 20:16:41 UTC 2012


On 21/02/12 18:34, Thomas Boehm wrote:
> John Veness wrote:
>> Personally I've never skipped forward or back by keyframe either, and
>> for me it's just an annoying step to get past (with the up/down arrows)
>> between Frame and 0.5 Seconds, both of which are useful. It would be
>> interesting to see if anyone really used Keyframe when editing, and if
>> not, just remove it from the list.
>
> I use it and it looks like MPEG-2 can only be cut on a keyframe, correct
> me if I'm wrong. I tried to cut on non-keyframes in the past and AFAIR
> there where always more frames in the show after cutting or less.
>
> I just tried it and cut 1500 frames from a show. The result after
> transcoding (ProjectX + HandBrakeCLI) had only 1462 frames.
>
> It looks like MythTV automatically sets the cut point to the preceding
> keyframe. I double checked my next trial before transcoding and the cut
> point was moved by MythTV when I set it to a non-keyframe...
>

It must surely depend on the tools being used.  ProjectX as used in 
mythcutprojectx often reports that it is 'dropping useless B-frames' - 
and as I said before, I have rarely used keyframe positions within the 
editor -  but I'm subjectively convinced that it isn't as coarse-grained 
as just cutting at keyframes.  Similarly I'm sure that more accurate 
cutting is possible;  nice as that would be, I'm just not sure it's 
worth pursuing in the general ad-cutting context.

Time I looked at the rapidly evolving web-based editor, perhaps?  A week 
ago I thought I needed a HowTo :-)

John P





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