[mythtv-users] Nuvexport, transcoding, and SVCD

[Chris Petersen]

> 1) If I am running PVR-250 cards, the .nuv files MythTV creates are already
> MPEG-2 files.  Yes?

correct.

> 2) Given #1 above, the default values for those files are not correct for
> the SVCD standard. Based on a tcprobe of my files, I have a bitrate of
> 16000kpbs, and SVCD is around 2500 (2520?) kbps.  Further, the audio should
> be at a bitrate of 44100 and I have 48000.  Correct?

SVCD can be anything, as long as the audio and video bitrates do not
exceed somewhere around 2720kbps (I round this down to about 2700
because some standalone dvd players seem to have issues if that bitrate
gets too high.  I'm not sure about the audio, actually.  Might explain
why some people have been having audio issues, since I don't change that
on output.  I'll have to look into a way to force toolame and mp2enc to
change the sample rate.

> Would that also explain the enormous size difference in my files vs. a real
> SVCD?  'Prox 700Mb for 45 minutes or so vs. 1.9Gb for 1/2 hr under Myth?

the bitrate will explain that, yes.

> 3) Therefore, I need to transcode the files to those values to be able to
> make a valid SVCD.  Transcoding splits apart the audio and video, resamples
> each component to the new specifications you request, and bundles them back
> together into a new MPEG2 file suitable for SVCD'ing.  Correct?

using nuvexport, yes.   Except for the audio thing that I just
mentioned.  I'll have to look into that.

> 4) If #3 is correct, can anyone give me valid command(s) for doing this? Or
> pointers to descriptions of the command-line tools that will let me figure
> this out?

look up info on the transcode package.  Otherwise, try my nuvexport
script with CVS mythtv.  If you use windows, you could also use a
program like TMPGEnc directly on your mpeg2 files.  TMPG is *much*
faster than mpeg2enc, and imho produces better quality encodes, too. 
However, it does NOT properly multiplex svcd files, so you either need
to re-mplex them with bbtools (windows) or tcmplex (linux).

> 5) The nuvexport script is actually a Perl-based attempt to do #4 above.
> Correct?

correct.

> 6) nuvexport, however, is :
>     -Not designed to work with PVR-250 cards?

false.  It *should* handle them just fine.  But because these nuv files
are actually mpeg2, there's less need to use nuvexport because standard
linux transcode packages can work directly on the files.  However,
nuvexport will let you deal with mythtv cutlists.

>     -Not designed to work with MythTV 0.11 tarball; it will only work
>      with CVS-based builds, post-0.11?

no, mythtranscode has gone through some significant changes in CVS, and
nuvexport requires these changes.  HOWEVER, mythtranscode has gone
through some significant changes (profile groups) since I've upgraded my
own cvs tree, and nuvexport may/may not work with these changes.  I'll
be upgrading my CVS sometime in the next day or two (hopefully), and
will add support for those changes then.

> 7) Once I have transcoded a MythTV recording, there are other "things" that
> go into making an SVCD.  Under Linux (Mandrake 9.1), what would be the
> suggested tools to lay out the SVCD and burn them?

You need vcdimager to make bin/cue files for your svcd (or you can just
drag the mpeg into nero in windows or Toast 6 in MacOS - I think that
toast 6 finally supports svcd).  If you look at
http://forevermore.net/myth/ you'll see a "chapterize" script - this
will create the bin/cue files for you, as well as add svcd chapter
points every 5 minutes (or other if you specify).

-Chris