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Re: Use of PCM and Vorbis in the Mobile Profile of SMIL 3.0

From: Jack Jansen <Jack.Jansen@cwi.nl>
Date: Fri, 10 Aug 2007 23:01:39 +0200
Message-Id: <9DC292A8-E2A5-44EA-8867-DF8BC2C834E9@cwi.nl>
Cc: "Philippe Le Hegaret" <plh@w3.org>, www-smil@w3.org, "Dominique Hazael-Massieux" <dom@w3.org>
To: Ivo Emanuel Gonçalves <justivo@gmail.com>

On 10-Aug-2007, at 18:05 , Ivo Emanuel Gonçalves wrote:
>> it *seems* that Vorbis requires more CPU to be decoded than a format
>> like AAC, thus rendering its use in a mobile environment more
>> problematic.
> This is certainly not correct.  Vorbis actually uses less CPU power
> than AAC.  The problem is that our optimizations were directed to the
> ARM platform, which is not what most mobile platforms use.

Are you referring to the fact that mobile platforms often have DSP  
chips or dedicated hardware for audio and video decoding here?  
Because I think that literally all mobile devices I've come across in  
the last couple of years seem to use an ARM for the main CPU...

If you're indeed referring to the use of coprocessors for media  
decoding: would you happen to know how difficult it would be to allow  
vendors to also decode Vorbis on such chips? There's probably a  
qualitative difference in difficulty for a vendor between (1) hiring  
a smart kid to write Vorbis DSP code and (2) getting into  
negotiations with your media chip supplier to get them to support  
Vorbis in the next release.

The distinction interests me, because in the second case the  
inclusion of Vorbis might actually hinder the acceptance of SMIL  
among mobile vendors.

Jack Jansen, <Jack.Jansen@cwi.nl>, http://www.cwi.nl/~jack
If I can't dance I don't want to be part of your revolution -- Emma  
Received on Friday, 10 August 2007 21:02:00 UTC

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