[vorbis] Ogg FLAC

Josh Coalson j_coalson at yahoo.com
Tue Oct 16 20:59:05 PDT 2001

--- rillian <rillian at telus.net> wrote:
> Um, I assume flac can do 24/96 and 5.1?

yep.  the format supports up to 32bps, 8 channels,
and impractically-high sample rate (~1MHz).

> elsewhere Josh wrote:
> > my overall vision would be to have an -ogg option to
> > flac that does what I mentioned, and a tool that can
> > convert between Ogg-FLAC and standalone FLAC, which
> > would also be very simple.  all of this I could do
> > pretty quickly if it would be really useful.
> That sounds reasonable, since you have an estabilished user
> community. 
> There's the extension-sorting issue to think of as well. It makes
> more 
> sense to use oggflac when you're multiplexing with other data. OTOH,
> as 
> jack mentioned you'd get our superior metatdata support. :^)

how does vorbis handle it?  I am assuming .vbs means ogg-
vorbis and the name for other_transport-vorbis is

FLAC metadata is very simple also, and I have it on my TODO
list to add a vorbis-style type to it, which would make
oggflac<->flac conversion trivial.

> You mentioned some redundancy in the framing. How did you do the 
> packetization?

the details are here (http://flac.sf.net/format.html) but
basically, in ogg-speak, FLAC has only pages, no segments
or packets.  pages may be variable length.  the page header
also contains the basic stream-level data you need to play
it, like sample rate, bits-per-sample, etc.

> Is there more you could throw away if you're using the
> ogg framing? Not that I should talk since I kept the chunk structure
> in 
> oggmng.

I could drop the sync code, sample number, the CRCs and
maybe the blocksize.  but this is maybe 0.2% or less of
overhead on CD-rate data.


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