[vorbis-dev] Re: comparisons

[Ingo Saitz]

MoiN

On Tue, Aug 22, 2000 at 07:12:30PM -0500, Nelson Rush wrote:
> -rw-r--r--   1 palisade users          4007318 Aug 22 16:31 tommy.ogg
> -rw-r--r--   1 palisade users          3989911 Aug 22 16:57 tommy.ogg.gz
> -rw-r--r--   1 palisade users          3991638 Aug 22 16:41 tom.mp3
> -rw-r--r--   1 palisade users          3959108 Aug 22 16:48 tom.mp3.gz

That is about 0.43% gain for the ogg stream, which seems very
doubtable to be useful. You should test with different tracks to
see if the compression gain is really worth.

But compressing the streams you loose the capability to seek to
an (almost) arbitrary position inside the file. The ogg and mp3
files are composed of a numer of small frames, giving you the
ability to start decoding in each frame. If you compress the
whole stream with gzip into a single file you have to decode
almost the whole file using gunzip if you want to play the last
seconds only.

There is an extention to gzip which uses some features to be able
to start decoding in the middle at ftp.dict.org/pub/dict. But the
overhead involved is somewhere around 0.5%.

So you would gain almost nothing compressing audio streams. You
loose the ability to seek and need more memory and cpu-power to
decode them.

    Ingo

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