[mythtv] MPEG2-MPEG2 transcoding: Illegal video stream

[Thomas Börkel]

HI!

Geoffrey Hausheer wrote:
> On 3/2/06, Thomas Börkel
>> I can also provide the first 10 MB of the original file, if necessary.
> Sorry I wasn't clear.  Yes, I need the 1st 10MB of the original, not the output.

OK:
http://www.boerkel.de/test_original.mpg

> The transcoder will start the offset at less than 1 frame (so the
> initial offset should be < ~40ms depending on the
> frame-rate/audio-rate).  However, each time you do a commerical
> change, you can increase your offset by as much as two audio frames

Can you prevent that from happening? Is this less likely, if I set 
cutpoints only on I frames?

Until Myth 0.19, I used avidemux do cut. OK, it can only cut reliably on 
I-frames, but I never got sync problems.

> (so you could be skewing the audio by 80ms per cutpoint).  In

Usually, I have a cutpoint at the beginning and end and then 2 for each 
comm break (normally 2 for a series). So, it's 6 cutpoints and this 
could result in up to 6 x 80ms = 480ms. Oh, oh...

> practice, it won't be that bad, but something to be aware of.  One of
> the reasons for the mpeg2<->mpeg2 transcoder in myth is that it
> actually pays attention to PTS values, and so doesn't muck up the A/V
> sync during processing (or at least it shouldn't)

Good. :-)

> For you to use these streams to burn to DVD, you need to specify the
> '--ostream dvd' flag, as ths will create NAV packets, which should

Where would I specify this? In the GUI? Or do I have to use 
mythtranscode from the command line?

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

> make it DVD compliant.  There really should be a line in the trancoder
> setup that lets you specify options like this, on a per-profile basis.

Yep.

> By the way, why would you convert mp2 to ac3?  You will incur a
> generational loss, and PAL DVD allows for mp2 as the only audio stream
> on the disc (NTSC doesn't, but in practice, I've never seen a DVD
> player that didn't support it)

My PAL Toshiba player does not recognize mp2 or ac3 automatically. I 
always have to go into the menu and switch manually. So, I normally have 
set it to ac3.

But that is not the only reason I demux/remux. I often want to use 
tcrequant on the video stream.

> I'll take a look at the issues you reported once you provide me with
> the original tream though.

Thanks. And thanks for the MPEG2 transcoding feature.

Thomas