[vorbis-dev] Using large-scale repetition in audio compression
xiphmont at xiph.org
Thu Sep 19 16:03:34 PDT 2002
On Thu, Sep 19, 2002 at 12:44:42PM +0200, Lourens Veen wrote:
> This idea is so simple that I'm sure it must have been thought of
> before, and discarded, since AFAIK it's not used anywhere. I did a
> quick web search but that didn't turn up much, so I figured I'd put
> it up for discussion here anyway.
> How about using large-scale repetition in audio compression? I'm
> thinking of redundancy in repeated pieces of a song, ie a chorus.
> Ofcourse, the different choruses aren't exactly the same (unless it
> was mixed digitally and they cheated :-)), but wouldn't there be at
> least some redundancy in the frequency domain? And could that be
> used to lower the required bitrate for repeated parts of a song?
This is one of the earliest things I tried in 1993. The answer was
'in fact, no'. The problem is not compressing the predictable parts
of a song; that's only a few bytes a second. The difficulty is
compressing the audible randomness.
The brute-force FFT/autocorelation compressor I wrote nearly ten years
ago know took several hours per song and when used in conjunction with
a standard LPC-style standard lossless compressor added as much
information to the stream as it eliminated.
In retrospect, this result should have been obvious.
> Obviously, it's not used (at least AFAIK) so there must be something
> against it. Anyone care to enlighten me?
"It doesn't work the way you think it does". Spend a few months on it
and you'll see why :-)
--- >8 ----
List archives: http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'vorbis-dev-request at xiph.org'
containing only the word 'unsubscribe' in the body. No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.
More information about the Vorbis-dev