[Vorbis] OGG decoding/multi-channel mixing

[Vamsi Mohan Reddy Pulagam]

Hi,

As far as Vorbis/Tremor codes show, I do not see any mixing operations. I 
only see a channel interleave operation. This means that for ex. if I encode 
two songs into an ogg stream like first song into the left and second song 
into the right channel, the decoded output will not be mixed output in both 
channels but interleaved output in respective channels, i.e., I hear first 
song in left and second song in right. So it all depends on how we encode 
the stream.

One thing that could be done is, since we have individual channel outputs we 
can mix them to a single channel and call this a mixed output (in the above 
example after doing this operation we will hear both songs in both channels)

And regarding mixing in frequency domain I am not sure about the feasability 
and complexity involved. But mixing in time domain is much simpler as far as 
I see.

Someone please correct me if I am on the wrong path.

Thank you,
Vamsi

----- Original Message ----- 
From: "Tor-Einar Jarnbjo" <tor-einar at jarnbjo.name>
Cc: <vorbis at xiph.org>
Sent: Wednesday, November 07, 2007 3:21 AM
Subject: Re: [Vorbis] OGG decoding/multi-channel mixing


> Joost Meijles schrieb:
>> Finally is it possible to mix OGG streams without first decoding them to 
>> PCM?
> Perhaps it would be possible to do the mixing in the frequency domain 
> before completing the decoding process by converting to PCM - (i)MDCT, but 
> it would be very difficult with the multiple window sizes used by Vorbis 
> and not make much sense, since the convertion between time domain data 
> (PCM) and frequency domain data is at least theoretically lossless. In any 
> case, the psyco-accoustic model must be applied to the resulting mix when 
> reencoding the data to achieve reasonable compression (rate and quality).
>
> Tor
>
>
>
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