[FFmpeg-soc] AAC Encoding - Where we stand, what's left

[Kostya]

On Wed, Jul 08, 2009 at 01:12:20AM -0400, Alex Converse wrote:
[...]
> 
> $ ./ffmpeg_g -i ../../Canyon-5.1-48khz-448kbit.ac3 out.aac
> ...
> $ mp4audec_mc out.aac out.wav 2>&1 | grep WARN | sort | uniq
> WARNING: only long windows are allowed in LFEs (winseq=1)
> WARNING: only long windows are allowed in LFEs (winseq=2)
> WARNING: only long windows are allowed in LFEs (winseq=3)
> WARNING: only sine shaped windows are allowed in LFEs (winshape=1)

At least it decodes...
And I admit that LFE lacks special treatment.

[...]
> >
> > Let's see:
> > bitstream.[ch] - bitstream writing. Of course we have that.
> > channels.[ch] - something related to multichannel. We have that.
> > filbank.c - MDCT. We have that.
> > huffman.[ch] - codebook coding. We have our own methods for coding.
> > tns.[ch] - you have an alternative implementation.
> >
> > What's left there:
> > aacquant.[ch] - we need to port it
> > backpred.[ch] - can be eliminated
> > fft.[ch] - we have one
> > frame.[ch] - nothing important
> > ltp.[ch] - can be eliminated
> > midside.[ch] - M/S coding. We have that already.
> 
> Does our mid/side work? It's not turned on.

Yes, but I still have to find an optimal way to detect it.
And you can enable it by uncommenting search_for_ms entry in coders in
aaccoder.c

> > psychkni.[ch] - we need to port it
> > util.[ch] - useless
> >
> > So, it's two or three useful files from whole bunch.
> >
> 
> One other big thing: Improvements to faac helps many people right now.
> People do (sadly) use faac for things. Improving the lavc encoder
> really only helps you and me until it's fit to merge, and who knows
> when that could be.
> 
> --Alex