[FFmpeg-devel] [PATCH 3/3] aaccoder: Improve IS phase rejection

Claudio Freire klaussfreire at gmail.com
Sat Jul 18 03:57:29 CEST 2015

On Fri, Jul 17, 2015 at 10:32 PM, Rostislav Pehlivanov
<atomnuker at gmail.com> wrote:
> That previous idea discriminated way too many bands for it to be actually
> useful. And it would require special cases for coefficients which 'blow up'
> and have an insane value.
>> What happened to the idea of comparing the energies of the addition
>> and diferrence and deciding on that?
>> It looked better at rejecting these cases than this one when we talked
>> about it.

>From my earlier testing, it's a bit too conservative, and if you make
it even more conservative, it may end up reducing the effectiveness of

But even if not used for avoding I/S, it can be used to pick whether
to invert the phases, where it was clearly more stable.

> This method is naive but it handles spikes better since a single spike in
> one channel will only cause a single phase to switch among a reasonably
> sized number of coefficients summed over.

The spike will be very audible though, and it should be ok if it
dominates. I don't remember any case where it was mistaken when I was

Do you have a sample that exhibits this?

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