[mythtv-users] Displayed recording duration not updated after applying cutlist

[Richard]

On 04/09/12 10:42, John Veness wrote:
> On 04/09/2012 00:30, Richard wrote:
>> I ended up writing a script
>> that would trim the start and end according to the cutlist, update the
>> start and end times of the recording accordingly and also filter out any
>> data stream from the recording, leaving all audio, video and subtitle
>> stream untouched (as I understand it, this should directly using
>> 'Recording profiles' but that never seemed to have any effect).
>> Depending on the channel and the amount of data streamed, the final file
>> is sometimes almost half the original size!
>>
>> Richard.
>
> Hi,
>
> I'm very interested in your script. I recording UK DVB-T and manually
> create a cutlist to cut out ads and trim the start and end. I would like
> to do a lossless transcode on this but this removes the DVB subtitles
> stream, which I sometimes use. Your script sounds like it will do the
> trick for me, will it?

Hi John,

Yes, it sounds like you want to do what I do.

The scripts are here:

http://dl.dropbox.com/u/19450259/trimRecording.pl
http://dl.dropbox.com/u/19450259/stripPIDs.pl

The first (trimRecording.pl) determines what needs to be trimmed from 
which file and handles all the database updates.  The second 
(stripPIDs.pl) is called by the first to perform the trimming/filtering.

Only the start and end are trimmed (based on a saved cutlist). 
'Internal' cuts are left alone (but still work after trimming).

stripPIDs.pl is mostly taken from the code here:

http://search.cpan.org/dist/Image-ExifTool/lib/Image/ExifTool/M2TS.pm

I pared it down a bit to get just what I needed so it's quite possible 
that some errors may not be caught but it works fine for me.

Only MPEG2 TS files will work with these scripts.  I use it with MPEG2 
and H.264 files without problem but very little checking is done that 
the files are in the correct format.  Most likely the script will abort 
with a 'Synchronization error' message but you've been warned!

The packet size is hard coded to 188 bytes.  Other sizes are apparently 
204 and 208.  It should be pretty straightforward to adapt it to these 
sizes if necessary, but I've not tried it as all my recordings use 188 
byte packets.

You can set trimRecording.pl up as a user job.

  -c <n>     Channel ID
  -s <s>     Start-time
[-M <path>] MythTV settings folder [HOME/.mythtv]
[-l <path>] Path to a directory or file to log to (default is stdout)

You will probably need to set the path for stripPIDs.pl in line 46 in 
trimRecording.pl.

trimRecording.pl moves the original recording into a subdirectory under 
the directory where the recording was found called 'orig'.

As a final warning: The Perl bindings are used to connect to the 
database.  Ideally all the database changes would be committed together 
and a rollback performed if something goes wrong, but unfortunately it 
doesn't seem possible to turn off auto-commits.  The database should not 
be completely screwed if something goes wrong but it's possible that it 
gets confused about the recording you were trying to trim - to the point 
of not being able to find it.

I use these scripts more or less daily and have at most an occasional 
database deadlock (which sounds worse than it appears to be - the script 
just aborts, everything else continues to work fine).  I've altered the 
script to leave the original recording where it is until the last 
moment, so even this error should be relatively harmless.

What I'm basically trying to say is 'caveat emptor'!

Richard.