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

Mike Melanson mike
Sun Mar 19 23:27:43 CET 2006

Oded Shimon wrote:
> Just thought I'd give a status report (and brag) - I can (almost) 
> successfully decode a AAC LC file created with faac! Decoder is very much a 
> mess right now, and I'm not gonna bother posting it here cause it will only 
> work with a very strict set of files (and even those not very well), but I 
> can proudly say I've given my decoder a bitstream and got back human 
> listenable audio... To further brag, it is almost 2 times faster than 
> faad2, even though I made no attempt at optimization. But this might change 
> when the deocder is actually complete...

	I'm not too surprised about the speed bump if you are using FFmpeg's 
get_vlc2() facilities. 5 of AAC's 12 VLC tables are implemented in FAAD2 
as tree-based decoders (the scalefactor tree may need to traverse up to 
19 levels). The weirdest part is that this approach is apparently 
recommended by the spec (I gather this from reading the FAAD2 comments 
about some academic paper on optimal AAC VLC decoding).

  *  Optimal huffman decoding for AAC taken from:

	-Mike Melanson

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