[mythtv-users] What happened to Lossless Transcoding for Cut Lists?

[John Pilkington]

On 19/04/2019 06:10, mythtv at kosowsky.org wrote:
> Ian Evans wrote at about 22:42:50 -0400 on Thursday, April 18, 2019:
>   > On Thu, Apr 18, 2019, 10:29 PM , <mythtv at kosowsky.org> wrote:
>   >
>   > > I recently upgraded from a very old MythTV to 0.29.1
>   > >
>   > > Before when creating transcoding profiles, there was a "tickbox" to
>   > > allow for lossless compression which was very useful for re-stitching
>   > > together the stream after cutting commercials without transcoding to a
>   > > new format.
>   > >
>   > > I see that there are ways to create user jobs via scripts, but this is
>   > > much more complicated (and lest robust) than the built-in tickbox.
>   > >
>   > > - Is there any reason the built-in lossless transcoding option was
>   > >   deleted?
>   > > - What is the simplest way to re-implement lossless transcoding post
>   > >   adding a cut list?
>   > >
>   >
>   > This might be related. Not near my system right now but thought I'd send to
>   > you.
>   >
>   > https://lists.gt.net/mythtv/users/611938
> 
> Seems like there is a bug...
> 
> In my old circa v23 version, I had the following entry in:
> 'recordingprofiles'
> 	(58,'Lossless','MPEG-4','MP3',6)
> where 6 is the profilegroup id corresponding to 'Transcoders'
> 
> 'codecparams'
> 	(58,'transcodelossless','1'),(58,'transcoderesize','0'),(58,'width','480'),(58,'height','480'),(58,'rtjpegquality','170'),(58,'mpeg4bitrate','2200'),(58,'mpeg4maxquality','2'),(58,'mpeg4minquality','15'),(58,'mpeg4qualdiff','3'),(58,'scalebitrate','1'),(58,'mpeg4optionvhq','0'),(58,'mpeg4option4mv','0'),(58,'mpeg4optionidct','0'),(58,'mpeg4optionime','0'),(58,'encodingthreadcount','1'),(58,'mpeg2bitrate','4500'),(58,'hardwaremjpegquality','100'),(58,'hardwaremjpeghdecimation','4'),(58,'hardwaremjpegvdecimation','4'),(58,'mpeg2streamtype','MPEG-2	PS'),(58,'mpeg2aspectratio','4:3'),(58,'mpeg2maxbitrate','6000'),(58,'low_mpeg4avgbitrate','4500'),(58,'low_mpeg4peakbitrate','6000'),(58,'medium_mpeg4avgbitrate','9000'),(58,'medium_mpeg4peakbitrate','11000'),(58,'high_mpeg4avgbitrate','13500'),(58,'high_mpeg4peakbitrate','20200'),(58,'samplerate','32000'),(58,'mp3quality','7'),(58,'volume','90')
> 
> In v29.1 fixes, the 'Lossless' profile is missing from
> 'recordingprofiles' though interestingly it still persists in codecparams.
> 
> In any case, I seem to have been able to fix the problem by *manually*
> inserting the missing entry into 'recordingprofiles' via mysql.
> 
> In particular, when I transcoded 'lossless' after adding a cut-list,
> the bitrate determined by ffmpeg was essentially unchanged.
> 
> The lack of the 'lossless' tickbox does seem to be a bug...
> 

IIRC most of the transcoder options used an obsolescent output format. 
mythtranscode --help still shows an -m or --mpeg2 option for the 
'lossless' cutting of mpeg2-encoded recordings, but TTBOMK there is no 
equivalent for the h264 codec.

John P