[mythtv] A prelude to transcoding MPEG2->MPEG2

[James L. Paul]

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On Monday 08 December 2003 13:17, Derek Atkins wrote:
> "Geoffrey Hausheer" <ou401cru02 at sneakemail.com> writes:
> > Note that I have yet to see a PVR250 stream which is DVD compliant.  DVD
> > requires either an AC3 or PCM stream to be present, and I'm not aware of
> > any way to get such a thing from the PVR250.  I've yet to find an AC3
> > encoder which is really compliant (the one that comes with ffmpeg is not
> > compatible with my DVD player, and I've had to use commercial encoders in
> > Windows to get compliant streams).  Anyhow, that isn't really relevant as
> > it has nothing to do with the issue at hand, I just thought I'd mention
> > it.
>
> Not quite true..  A DVD can also use MP2 audio, which the PVR will do.
> I was able to make a video DVD without any audio transcoding, and
> it works just fine in my set-top DVD player.

I just posted to this effect as well. Here's some specifics on DVD support for 
MPEG audio, from the excellent dvddemystified.com website:

MPEG audio is multi-channel digital audio, using lossy compression from 
original PCM format with sample rate of 48 kHz at 16 or 20 bits. Both MPEG-1 
and MPEG-2 formats are supported. The variable bit rate is 32 kbps to 912 
kbps, with 384 being the normal average rate. MPEG-1 is limited to 384 kbps. 
Channel combinations are (front/surround): 1/0, 2/0, 2/1, 2/2, 3/0, 3/1, 3/2, 
and 5/2. The LFE channel is optional with all combinations. The 7.1 channel 
format adds left-center and right-center channels, but is rare for home use. 
MPEG-2 surround channels are in an extension stream matrixed onto the MPEG-1 
stereo channels, which makes MPEG-2 audio backwards compatible with MPEG-1 
hardware (an MPEG-1 system will only see the two stereo channels.) MPEG Layer 
3 (MP3) and MPEG-2 AAC (also known as NBC or unmatrix) are not supported by 
the DVD-Video standard. MPEG audio is not used much on DVDs, although some 
inexpensive DVD recording software programs use MPEG audio, even on NTSC 
discs, which goes against the DVD standard and is not supported by all NTSC 
players.

> > .Geoff
>
> -derek
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