[FFmpeg-devel] [RFC] AAC Encoder

[Michael Niedermayer]

On Mon, Aug 18, 2008 at 02:05:43PM +0200, Gabriel Bouvigne wrote:
> Michael Niedermayer a ?crit :
> >>            switch(last_window_sequence){
> >>            case ONLY_LONG_SEQUENCE:
> >>                win[ch] = switch_to_eight ? LONG_START_SEQUENCE : ONLY_LONG_SEQUENCE;
> >>                grouping[ch] = 0;
> >>                break;
> >>            case LONG_START_SEQUENCE:
> >>                win[ch] = EIGHT_SHORT_SEQUENCE;
> >>                grouping[ch] = pch->next_grouping[ch];
> >>                break;
> >>            case LONG_STOP_SEQUENCE:
> >>                win[ch] = ONLY_LONG_SEQUENCE;
> >>                grouping[ch] = 0;
> >>                break;
> >>            case EIGHT_SHORT_SEQUENCE:
> >>                win[ch] = switch_to_eight ? EIGHT_SHORT_SEQUENCE : LONG_STOP_SEQUENCE;
> >>                grouping[ch] = switch_to_eight ? pch->next_grouping[ch] : 0;
> >>                break;
> >>            }
> >>            pch->next_grouping[ch] = window_grouping[attack_n];
> > 
> > 
> > this is limited to 9 of 256 possible groupings, not to mention that i have my
> > doubts about the optimality of the highpass based selection.
> 
> For the only 9 possible grouping, I agree that it's not optimal (please 
> remember that the 3gp reference model is provided by Coding Technologies 
> which also need to be able to sell their own encoder).

"remember" requires me to know it first ;)


> Regarding the highpass method, if the highpass freq is properly choosen, 
> it's a method that demonstrated its usefullness. Its main drawback is 
> usually the computation time compared to spectrum-based methods which 
> can often be done using data that is already computed.

And how does one properly choose it?
Is it content dependant, if so i really have my doubts about it being a
good choice as algorithm.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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