[mythtv-users] Re: Anyone tried MPEG2 to MPEG2 transcoding?

Simon Kenyon simon at koala.ie
Thu Jul 21 17:30:57 EDT 2005

On Thursday 21 July 2005 18:41, Cory Papenfuss wrote:
> > On Thursday 21 July 2005 17:09, Cory Papenfuss wrote:
> >> The problem (as I've painfully discovered and discussed before) is
> >> that the ivtv cards change the audio and video relative timestamps (PTS,
> >> DTS, etc).  That information is at the PS level, and avidemux blindly
> >> strips PS into A and V.  If the sync offset isn't constant, it gets off
> >> as the clip progresses
> >
> > have you asked the ivtv bods if they could "fix" this?
>  	I haven't but it's not the fault of the driver.  I believe that
> the chip itself does it when it gets a bogus packet.  Basically, since
> everything is a convoluted mess of interleaved audio and video frames,
> when a video frame comes up short (like an analog glitch in a VHS tape
> capture for instance), it's much easier to just throw that frame away and
> change a time offset.  All of the other frames are still in buffers and
> don't need to be messed with.
>  	... or at least that's how I rationalize it.  If the ivtv driver
> were to look for this, it would basically have to do everything we're
> talking about, but in the driver kernel space (not good).  Basically, the
> streams produced aren't incorrect, they're just a little more complicated
> than the simplistic streams that 95% of the linux software mpeg utilities
> out there expect

ok, but nevertheless, it might be worth asking them

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