[Ffmpeg-devel] ac3 encoder

Justin Ruggles jruggle
Mon Apr 18 23:32:09 CEST 2005

I've been playing around with the AC3 encoder in ffmpeg hoping to make 
some improvements.  Right now I've added stereo matrixing for 2-channel 
audio, and I've been experimenting with some different exponent strategy 
algorithms.  I've made an attempt at block switching, but can't figure 
out how to get the short-block mdct to work with fft, so right now it's 
extremely slow doing it the O(n^2) way.  I have plans to try my luck at 
channel coupling as well.

Anyway, I have one question.  Is there anything inherent about ffmpeg 
that requires the encoder to use 16-bit input?  The AC3 format uses 
24-bit resolution internally.  I've reworked the code a bit to use 
floating-point input for my purposes, but I was going to submit some of 
my changes to ffmpeg at some point.  So I'm wondering if using 
floating-point or even 24-bit integer input would integrate with ffmpeg 
or if the 16-bit input is for a particular reason other than the fact 
that it's so common.


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