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

Gabriel Bouvigne bouvigne
Mon Aug 25 15:22:09 CEST 2008

Michael Niedermayer a ?crit :

>>1. Perform some input filtering (lowpass, highpass, stereo attenuation, whatever)
> Its debateable in how far this should be here or seperate and outside of the
> encoder.

While highpass (mainly in order to remove DC) might belong to a general 
"preprocessing" step, highpass and stereo attenuation, while being 
filtering operations, might/should actually be driven by the encoder 
itself (psymodel or encoder core). So even if right now they are using 
fixed parameters, it might be a good thing to provide provisions within 
the interfaces to set up parameters of those filtering operations per frame.


*stereo attenuation depends of current complexity of input. If the 
encoder is easily able to encode the input, there is no point in 
performing stereo atenuation.

*lowpassing might increase temporal smearing in case of transcients, so 
it might depend on attack detection.

Gabriel Bouvigne
personal page: http://gabriel.mp3-tech.org

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