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Re: 1. MP3 or AAC mixing in compressed/coded domain (2)

Mixing two encoded streams is different than editing a single one. 

-----Original Message-----
From: AUDITORY - Research in Auditory Perception
[mailto:AUDITORY@xxxxxxxxxxxxxxx] On Behalf Of Matt Flax
Sent: Monday, March 02, 2009 3:05 PM
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: Re: 1. MP3 or AAC mixing in compressed/coded domain (2)

There are applications which work in the compressed domain ... this is
not a new concept. The reason is that each time you uncompress edit and
re-compress, you loose audio quality. For that reason people have long
been doing it.

Here is an example application :

Further, video editors (such as Sony Vegas) tend to be rather limited in
their audio resolution. In other words, they don't let the editor go
down to the sample for cuts ... normally, the video editors are broken
into blocks of samples which are of a video frame's length in time.
The majority of audio editors do allow to the sample editing. Now, that
said, there may be limitations in editing MPEG encoded audio down to the
sample, as they tend to be block based algorithms.


On Mon, 2009-03-02 at 09:29 -0800, Crockett, Brett wrote:
> Sony Vegas is a DAW as well as video.
> If I understand the question, he's asking about mixing in THE CODED 
> DOMAIN and not doing a decode, mix and re-encode.
> You can't do that easily and there are no commercial mixing solutions 
> available.
> -----Original Message-----
> From: AUDITORY - Research in Auditory Perception 
> [mailto:AUDITORY@xxxxxxxxxxxxxxx] On Behalf Of Lorenzo Picinali
> Sent: Monday, March 02, 2009 2:47 AM
> To: AUDITORY@xxxxxxxxxxxxxxx
> Subject: 1. MP3 or AAC mixing in compressed/coded domain (2)
> Dear All,
> I'm not sure I've understood properly, but it seems to me that Sony 
> Vegas is not a DAW, but a video editing software...
> It is plenty of audio editing and mixing software that can open MP3 or

> AAC (AC3) files, but what they do is they all convert the compressed 
> files in an uncompressed PCM format, and then perform all the mixing 
> and editing operation, and convert them back to the compressed format 
> after the processing. This is fore sure a good method with short 
> files, but having for example a ten ours MP3 stereo recording, on a 
> normal PCM format would be nearly 10 Gb of data, therefore for mixing 
> and editing directly in MP3, in this case, could be a very good idea.
> I'm not aware of any available software that directly mixes compressed

> files, but for the editing you could use http://mpesch3.de1.cc/ , 
> which allows you to cut MP3 files and change the volume...
> A friend of mine has been working on a software for the mixing 
> directly in compressed format (Dr. Giancarlo Vercellesi, you can find 
> online some of his publications), and there are some software 
> prototypes for this, but nothing available yet...
> Yours
> Lorenzo Picinali
> Lorenzo Picinali
> Faculty of Technology
> De Montfort University, The Gateway
> Leicester, LE1 9BH
> lpicinali@xxxxxxxxx
> Tel 0116 207 8051
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