[FFmpeg-devel] Blu Ray drive donation

Jean-Francois Thibert jeanfrancois
Tue Mar 17 15:39:40 CET 2009

On March 17, 2009, Ian Caulfield wrote:
> 2009/3/16 Justin Ruggles <justin.ruggles at gmail.com>:
> > Apparently there are some streams that mix regular AC-3 and TrueHD in
> > the same substream. ?It seems the TrueHD frame is placed after the AC-3
> > frame. ?I'm not sure if it provides additional channels or is a lossless
> > version of what's in the AC-3. ?My first guess is that it's the same
> > audio encoded twice because TrueHD is an optional codec in Blu-ray, but
> > AC-3 is mandatory. ?Maybe it's both..lossless version of 6 channels plus
> > extra channels. ?Anyone else know more about this? ?Or better yet, have
> > some samples?

Both streams are independant in that case.

> I had a sample, although I can't seem to locate it now. It had an AC-3
> and a TrueHD version of the same track, encoded as two streams with
> different extended_stream_ids but muxed onto the same PID. I did look
> at adding support for this, but the current mpegts demuxer relies on
> one PID == one stream, so I didn't know how to proceed...
> Ian
> _______________________________________________

You will notice that you can extract the core AC3/DCA streams by selecting 
only packets that have the priority bit set in the transport stream header 
and the extended stream in those that have the priority bit cleared.


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