[vorbis] Exact nature of RC2 re-encode bug

[Beni Cherniavksy]

On 2002-01-04, Geoff Shang wrote:

> Hi:
>
> I just wanted to know where exactly the problem with re-encoding in RC2
> was.  Was it in vorbis' ability to cope well with its own output as input,
> or did the first encode produce output that didn't lend itself to
> re-encoding?
>
> The difference is important.  If it's the latter, anyone wanting to
> re-encode material will have to first encode it with RC3.  I guess what I'm
> asking is, will material intended for re-encoding at lower rates etc, need
> to be encoded again under RC3 or will material encoded under RC2 perform OK
> now?
>
Why would you re-encode vorbis in order create a lower-rate version?  For
vorbis features the bitrate-peeling capability.  You shouldn't re-encode
unless you need lower-quality versions today.  There are yet no tools for
doing the peeling but files produced by surely RC2 and I think RC1 too,
are suitable for (future) peeling.  It was even promised that it would
eventually be possible to take and old unsitable file (e.g. beta3) and
re-arrange it losslessly, without re-encoding, to make them peelable.


-- 
Beni Cherniavsky <cben at tx.technion.ac.il>
                 (also scben at t2 in Technion)
Happy new 2 (mod 100).

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