[vdr] Re: DVD and MPEG Audio

[Dave Chapman <dave@dchapman.com>]

On Thursday 25 July 2002 15:53, Stephan Schreiber wrote:
> According to DVD specifications there must be at least one PCM or AC3 track,
> but most stand-alone players don't complain if you present them only mpeg
> audio.

Yes and No. :-)

PAL disks must have MPEG or Linear PCM audio (AC3 is optional)

NTSC disks must have AC3 or Linear PCM audio (MPEG is optional)

So PAL video with only MPEG audio is a perfectly legal disk. (but NTSC with 
only MPEG isn't).

There are many easily available AC3 decoders, but AC3 encoders are very rare 
(and expensive).  You don't gain anything by converting the MPEG audio 
broadcast over DVB into AC3 - so the lack of an AC3 encoder isn't a problem.

You also shouldn't confuse "AC3 encoding" with "AC3 multiplexing" - i.e. it 
should be relatively straightforward for an open source DVD authoring tool to 
mutiplex AC3 audio recorded from (for example) Pro-7 into the VOB.  The 
actual encoding is the hard part.

Regards,

Dave.