[vorbis] [new?] Streaming technique

[Michael Smith]

At 12:57 PM 6/5/01 +0200, you wrote:
>Hi,
>I have a newbie question, and a not-so-newbie one. I've just found 
>out about Ogg, and I haven't been able to find a clear answer in 
>the many webpages this proyect has (btw, why not create just one 
>site instead of vorbis.com, ogg-vorbis.com...).

There are only two websites - the main one at vorbis.com, and the
developer one at www.xiph.org/ogg/vorbis.

>The question is, does Ogg use perceptual coding, like mp3 does? And 

Yes, it's a perceptual codec.

>if so, would it be possible to build an encoder in such a way as 
>to take one input stream and make it produce 2 different files? One 
>file encoded at 64kb, and the other file with the information dropped 
>from the stream that would have made the resulting encoded stream 
>128kb? What I mean is a way to produce 2 64kb files which could be 
>somehow "added up" on the decoder to produce a 128kb stream. Is there 
>a name for this kind of thing, or have I just made it up?
>I hope I've made myself clear enough, but if not just say so and 
>I'll try to explain better.

Your question isn't entirely clear. However....
Vorbis has a feature called 'bitrate peeling' (note that there aren't
any tools to do this currently, but the format itself is capable). This
would allow you to encode a 128 kbps stream, and either decode that as-is,
or 'peel' it to lower bitrates. So you could produce (without having to
reencode) a 64 kbps stream from this.

Michael
 

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