[mythtv] MPEG2-MPEG2 transcoding: Illegal video stream

Thomas Börkel thomas at boerkel.de
Fri Mar 3 09:34:00 UTC 2006


HI!

Geoffrey Hausheer wrote:

> sorry, I meant 2 frames per cutpoint pair so it is half that.  That is
> also a theoretical number.  In practice it will never be this bad, and
> could be in the 1-10ms range depending on your encoding frame-rates

Ah, OK.

>>Where would I specify this? In the GUI? Or do I have to use
>>mythtranscode from the command line?
> 
> You need to use the command line until I add a GUI item.

About that --ostream dvd option: IMHO, this should be the default. I 
think, many people cut the video to archive it on DVD. And if not, those 
DVD nav packets would not hurt much, right?

>>I once tried mythtranscode 0.19 from the command line, but it ignored my
>>cutlist. I tried by specifying the filename and by specifying
>>channel/start time. I used options --mpeg2 --honorcutlist --showprogress
> 
> those look fine.  you need to use --starttime and --chanid instead of
> --infile if you want to pull the cutlist from the database.

I tried. Still it ignored my cutlist in 0.19.

>>But that is not the only reason I demux/remux. I often want to use
>>tcrequant on the video stream.
> 
> Interesting.  One option here is to allow myththrancode to call
> external applications on the elementary streams as it runs, and to let
> mythtranscode handle stitching the streams back together.  I'll have
> to think about that.  Of course changing the format (like doing an
> mp2->ac3 conversion) would make things more complicated, so maybe that
> is something best handled by mythtranscode itself.  It has always been
> my goal to have mythtranscode be able to spit out DVD compliant
> streams, though that goal may be a long way off, as there are some big
> hurdles in the way.

I have 3 use-cases besides just watching/deleting the recordings. This 
is how I did before Myth 0.19 (now I can cut with Myth instead of avidemux).

1.
A friend missed the show and I want to give it to him. So I just burn it 
to DVD with no cutting. Today I use mpeg2desc, mplex -f 8, dvdauthor, 
growisofs in an automatic script.

2.
I want to archive the show and it fits on one DVD. So, I cut it with 
avidemux, save video/audio seperately, convert audio to ac3 with ffmpeg, 
mplex -f 8, dvdauthor/TMPGEnc DVD Author and growisofs. Besides 
avidemux, this is a script.

3.
I want to archive the show, but it is too big. So, I cut it with 
avidemux, save video/audio seperately, tcrequant video, convert audio to 
ac3 with ffmpeg, mplex -f 8, dvdauthor and growisofs. Besides avidemux, 
this is a script.

So, since ffmpeg and transcode are already present on Myth boxes, 
mythtranscode could use them.

For my use-cases, it would be perfect, if mythtranscode could convert 
the audio and optionally requant the video. And, as I said above, the 
result should always be DVD compliant.

Next step would be some DVD mastering code like VDR has, but this is not 
as good as TMPGEnc DVD Author for example, so it is not that necessary 
for me.

> I need more input about your specifci issues, since I can't reproduce
> them so far.

This has been resolved.

Thomas


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