[FFmpeg-devel] AAC decoder round 9

madshi dear
Thu Aug 21 09:52:03 CEST 2008

Robert Swain schrieb:
> They were previously OKed. I have committed everything I want to
> commit to trunk, from SoC now and enabled the AAC decoder. I will post
> a news article on ffmpeg.org shortly with the additions since the last
> one.
> I'd like to extend my sincere gratitude to Michael for all his
> reviewing efforts and his perfectionism, to Kostya for all the
> assistance and suggestions he's given me and to anyone else who...
> helped made this possible. Hehehe. :) Thank you very much. If we were
> in closer proximity I would suggest we have a partay. ;)
> Of course, it doesn't end here. I will add myself as the maintainer of
> the AAC decoder files. I intend to fix bugs, continue clean up of bits
> that remain to be tended to that were not of immediate priority and to
> add SBR and PS support.
> Best regards,
> Rob

Congrats!  :-)

I've a few questions, if you don't mind:

(1) How exact is the AAC decoder specification? In other words: Can there
be a difference in audio quality between different decoders (other than 
of course)? Would you say that using your new libav decoder should
deliver similar quality to e.g. Nero's AAC decoder?

(2) Does AAC have a native bitdepth? Or is it similar to AC3/DTS where
the decoder basically outputs floating point? In the latter case: Which
bitdepth output variations does the decoder support? I'm sorry, I'm a
bit out of the loop on where libav stands now in terms of audio bitdepth.
A while ago floating point output was not possible with many decoders.
Maybe that has changed in the meanwhile?

(3) Missing SBR and PS support probably means that the decoder can't
decode some AAC files? Will it abort processing in that case? Or will it
decode with lower quality? (I think I'd prefer aborting.)

(4) Which format does the decoder expect/support? With ADIF/ADTS
headers? Or just the raw data without any headers or something else?

Thank you!

Regards, madshi.

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