[FFmpeg-devel] [PATCH] AAC Encoder, Round 2

[Michael Niedermayer]

On Mon, Aug 25, 2008 at 01:09:54PM +0300, Kostya wrote:
> On Sun, Aug 24, 2008 at 09:27:44PM +0200, Michael Niedermayer wrote:
> > On Sun, Aug 24, 2008 at 09:05:54PM +0300, Kostya wrote:
> > > On Sun, Aug 24, 2008 at 06:45:58PM +0200, Michael Niedermayer wrote:
> [...]
> > > > > 3. Encoder performs windowing and MDCT (and grouping?)
> > > > 
> > > > i dont think grouping can be done at this point, at least not optimally.
> > > 
> > > well, from my POV, you can just merge groups with similar scalefactors after
> > > they are known
> > 
> > well you dont know the scalefactors yet ...
> > besides what is "similar"
>  
> I've seen two empty consequent window groups in a frame sometimes that could be
> merged, otherwise I can't say how to perform grouping.
>  
> > > > > 4. Model calculates perceptual entropy and thresholds
> > > > > 5. Ratecontrol module in encoder uses them to produce final thresholds
> > > > > 5.1 maybe it will call psy model to calculate perceptual distortion for the band
> > > > > 6. Encoder quantizes input with scalefactors
> > > > > 7. Encoder determines and encodes band info and coefficients
> > > > > 8. Fetch next frame and goto step 1 unless it was the last frame
> > > > > 
> > > > > Any ideas/suggestions/patches?
> > > > 
> > > > Iam not sure, this is quite vague
> > > > 
> > > > 
> > > > A few points that are IMO important
> > > > * decissions must NOT be bundled into psy models, that is when we implement
> > > >   3 differnt heuristics to choose the MDCT/window size they must be choosable
> > > >   independant of the remaining unrelated psy model, this also applies to
> > > >   things like stereo attenution coeffs, the way low/highpass cutoff is
> > > >   choosen and so on ...
> > > 
> > > then how? select separate module for each psy step?
> > 
> > not sure i would call it "module" but yes in princple
> > 
> > i was more thinking of 
> > if(avctx->something == something){
> > }else{
> > }
> > though, the struct, function point, ... system seem a little overkill here
> 
> So, should I reduce psy model to filling up Psy3gppBand data and move
> rate control and quantization to encoder?

yes, i think so


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data
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