[mythtv-users] Lossless Cut and keyframe cuts off

[John Pilkington]

On 14/11/12 13:33, Doug Vaughan wrote:
> Ian,
>      It seems that mkvmerge which is used for both cutting and merging
> processing has odd issues with HDHomerun recording devices. What is
> weird is that issues crop up on specific channels not in general on all
> channels. I believe that the issue you describedhas already been noted.
> There is nothing that Lossless Cut can do about it. I have investigated
> other cut/merge utilities and combinations but all have their own flaws
> and draw backs.
>
> To me mkvmerge is the best of the lot and I hope it continues to gets
> enhanced.
>
> See bullet #6:
> http://www.mythtv.org/wiki/Lossless_Cut#Known_Limitations
>
> Sorry Ian there is nothing I can do. Hopefully most of your HDHomerun
> recordings can be properly cut by mkvmerge.
>
> Doug
>

AIUI the HDHomeRun stores the programme stream as encoded before 
transmission. The keyframes are inserted during encoding and/or editing 
before transmission and any keyframe-based editor (assuming the 
keyframes are correctly identified) will cut at one of them; you can 
just choose which one, and should allow for that during editing.  You 
may well find that different production companies work to different 
guidelines.

Lossless mpeg2 mythtranscode tried to decode and recode to give 
frame-accurate cuts but had trouble with irregular spacing of keyframes 
and stop-start streams.

HTH

John P