[mythtvnz] Cutting H.264 DVB-T files with ffmpeg without transcoding

[David Moore]

Craig Blaikie wrote:
>> I've used VB a fair bit also but I don't think it's a good idea to rely
>> on something which isn't pretty standard in Ubuntu for portability
>> reasons. Turns out sql in bash is really simple. Just echo the sql
>> commands through a pipe to mysql and catch the results. Dead easy. :-)
>> Hardest thing will be understanding which tables need updating.
>> Recordedseek and recordedmarkup are the ones I know of so far.
>>
>> Actually looks like the trickiest thing is handling the cuts. Myth cuts
>> in recordedmarkup table are in frames whereas ffmpeg uses times so need
>> to do some maths to convert frame to time. Bash doesn't do floating
>> point maths but there is a linux utility called bc to do this so that's
>> no problem. Could be a problem with cut accuracy however. I had a look
>> at one of my recordings last night and it seems that the time myth shows
>> for the cut points is not exactly equal to the cut point frame number x
>> 25 (fps). I'm guessing there might be some issue with the start time for
>> the recording but not sure yet.
> 
> [Craig Blaikie] 
> I haven't seen the frame offset issue in MythTV, is it only in the final
> ffmpeg'ed file?  If it's a constant offset then it might be easier to add an
> adjustment/offset value. 
> Looks like mythcommflag can do most of the heavy lifting with --getcutlist
> which returns a nicely formatted set of cut points, (still in frames) then
> using --clearcutlist and --rebuild to reset the seektable.  I'll have a go
> at putting it together, might take me a few days...
> 
> Cutlist: 0-1220,17379-21140,33779-39043,49604-54116,66654-71917,83563-136461
> 

What I have seen is when you're editing a recording in myth it displays 
the time for the cut points. But when you look at the frame numbers in 
recordedmarkup they don't exactly match the times displayed by myth. I 
haven't checked a final file yet.

The cut list wasn't so hard after all. Simple use of mysql to store the 
cuts and cut types in an array and then a little code to convert to 
times and use them in ffmpeg.

I'm thinking I'll use mythcommflag for the final cleanup to rebuild the 
seek table and clear the cutlist.