[linux-audio-user] DVD audio authoring

[kevin ernste]

--- Steve Harris <S.W.Harris at ecs.soton.ac.uk> wrote:
> On Tue, Aug 26, 2003 at 10:05:37 -0700, kevin ernste wrote:
> > In the studio I work in, we do DVD-A authoring under another OS
> with a
> > standard $300 4x Pioneer DVD-R/RW and have done up to 8 channels of
> > 24/96 using something called Meridian Lossless Packing
> > (http://www.ambisonic.net/mlp.html).  The software is rather
> spendy,
> > but nothing near $4K.
> 
> MLP is patented 6 was to sunday, I doubt your going to see a free
> implementation anytime soon. Its possible that as a comminity we
> could
> licence the format, but I suspect we would still have to pay a per
> seat
> licence fee, so it would not be free or Free.
> 
> The software implementation Meridian sell costs about EUR2500. I'm
> actually very supprised that the Pioneer box does realtime MLP coding
> because as I understand it (war stories from someone in the film
> industry)
> the first pass doesnt always succeed, sometimes you need to discard
> some
> information before it can squeeze the audio into the (fixed) audio
> bandwidth allocation. Maybe this stage has been automated, or the
> DVD-A
> spec allows more bandwidth.

The Pioneer doesn't do the real-time MLP encoding, it's done in
software.  An encoding app writes an .mlp file which is then burned
from a separate tool.

The fixed bandwidth starts to shrink _fast_ with 24/96 and multiple
channels.  4 is usually safe, 6 can really be asking for it.  If I
remember correctly, the data rate for 6 channels of uncompressed 24/96
is close to 14 mbs, while DVD needs less than 9.6.

Compromises have to made sometimes, say if you have a spot in a mix
where all bits are on in all channels simultaneously, it won't work. 
If there is an error or situation that cannot be handled as-is, the
encoder we use can "re-bit" if desired, including smart (even
automatic) 'effective bit' reduction.  So, for example, it can be set
to take bits from the rear before the mains.

Sometimes this is unacceptable and the track(s) must be remastered, but
this is suprisingly infrequent.  Most people in this studio are doing 4
channels anyway (ambisonic b-format, decoded as "square").

Regardless of MLP (highly unlikely, as you say, because of patents) or
something like it, DVD-A support for linux would be a great thing.

Kevin

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