[Ffmpeg-devel] [PATCH] faad decoding error return

Mike Melanson mike
Sun Mar 5 17:07:50 CET 2006

Diego Biurrun wrote:
> On Sun, Mar 05, 2006 at 12:33:55PM +0000, M?ns Rullg?rd wrote:
>>Any volunteers to write a proper AAC codec?
> Now that would be wonderful..
> Maybe we can try out an idea I've been having for a long time and put
> out a bounty for an AAC implementation.  I'm willing to put, say, 50EUR
> where my mouth is, if a few others join in maybe we can motivate
> somebody to finally implement this.
> Also see Mike's writeup about AAC in the wiki:
> http://wiki.multimedia.cx/index.php?title=Understanding_AAC

	I'm glad interest has flared up on this matter again. It may motivate 
it me to complete our real "open" AAC description. As I see it:

* FAAD decodes AAC data
* we have the source code for FAAD
* we can reverse engineer and document the AAC algorithm from FAAD
* we can create a fresh implementation from that new documentation

I have a bunch of notes that I still have not placed into the Wiki. I 
will try to get to that soon. I am woefully underskilled when it comes 
to perceptual audio codecs but I have formulated this rather naive, 
reductionist view of the perceptual audio decoding process:

* decode a bunch of parameters and transform coefficients from bitstream
* run those parameters and coefficients through a series of transforms 
to produce PCM data

The first priority in the documentation-reimplementation process for AAC 
should be what is called the low complexity profile. This is most 
commonly seen in Apple QuickTime files, including iTunes files.

	-Mike Melanson

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