[vorbis] reencoding OGG Vorbis

[Gregory Maxwell]

On Wed, Feb 21, 2001 at 08:15:01AM +0100, Moritz Grimm wrote:
> Inspired by the discussion about mixing Vorbis streams and so on I came
> to the question whether Vorbisstreams can be, just like MP3, reencoded
> without further loss.
> 
> As I heard, and I am pretty sure that it's true, MP3 files can be
> decoded and reencoded unlimited times without further quality loss (of
> course the same encoder with the same preferences has to be used all the
> time). Is this also possible with .OGG?

I'd like to see the mp3 encoder which does this. In prior expirments I found
that all the mp3 encoders I could find would eventually reach a almost
steady-state output after many encode-decode cycles, but the output sounded
much worse then the first generation.

In a simmlar test, Vorbis faired much better. However, there are many
decisions made based on the content of the audio (window switching, floor
shape, etc) so it's unlikely that 'lossless' reencoding is possible with the
current encoder.

However, in actual tests, vorbis fairs well.. I ran audio through a number
of encode/decode cycles (I believe 50) and ended up with something that
sounded just like the orignal on a quick surface listening.

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