[mythtv-users] Solved: CC (and maybe Teletext) to DVD

[faginbagin]

Hi Anthony,

Have you had a chance to experiment with gopchop?

 > My understanding, in a simplistic manner, is that MPEG has a Group Of
 > Pictures (GOP) which basically is a frame that is the complete picture,
 > and then a series of diffs to this first frame.  So, if you cut on a GOP
 > marker, you can cut from there to the next GOP marker losslessly.  But
 > how the subtitles are folded into the GOPs, I don't know.  I'm fairly
 > confident that some subtitles will survive cutting a recording using
 > gopchop.  I'm not confident in what the result will be as I could see
 > several different possibilities, worse case the subtitles are not cut,
 > and they get further and further off with each subsequent cut in the
 > video stream.

I think I can clear up some of this. When there are subtitles present, 
they should be in a separate stream from the video and audio, each of 
which are in their own streams. The streams are interspersed with each 
other in a MPEG-2 file, in the form of packets. Each packet has a header 
that identifies the stream type, amongst other things like time stamps 
and the length of the packet. So, if gopchop works by locating stream 
packets where GOPS begin and extracts from that point forward, the video 
AND all other stream packets (subtitles as well as audio, and possibly 
more than one of each), it should preserve the subtitles. But, if it 
makes assumptions about what the user wants and drops secondary audio 
and subtitle streams on the floor, then you'll lose subtitles.

BTW, I just saw your question about mytharchive dvd themes a few weeks 
ago. You might want to look at the python script I included with 
cc2subtitles called tweakdvdxml.py. As the name implies, it tweaks the 
dvdauthor.xml produced by mytharchive to do part of what I think you 
mean by "autoplay". Once you choose a title, it will automatically play 
the titles that follow. If you also want it to automatically play the 
first title after displaying the menu for a some length of time, I think 
you can do that by changing the pause="inf" attribute in the <pgc> tag 
for the first menu. Hope that makes sense.