[vorbis] mixing and 'downgrading' of vorbis-files

[Eliot Blennerhassett]

On 19 Feb 2001, at 10:03, Mercier, Dave wrote:

> The same arguments would probably apply to any frequency domain type of
> compression (MP3, AAC, etc.).
> 
> Well I don't really know that much about the Vorbis format so correct me if I am
> wrong on any points.

For MPEG layer 2 or 3,  it is possible to mix streams of the same samplerate 
in the frequency domain.  This definitely saves processing power, because 
the "matrixing and subband filtering" stage only needs to be run once over 
the mixed output. This stage is typically about 60% of the total MIPS of a 
single stream decoder.

It depends on the implementation whether the resulting quality is 
better,same or worse than doing pcm mixing.

I am not sure whether Vorbis has an analogous structure that allows this 
kind of mixing.

regards

=================================================
Eliot Blennerhassett                       *:-{)>
AudioScience, Inc. (New Zealand Office)
6 Centaurus Rd             
Christchurch 8002          Mobile: +64 21 1183531
New Zealand                Ph/fax: +64  3 3327818
eblennerhassett at audioscience.com
<http://www.audioscience.com>
=================================================

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