[FFmpeg-devel] Help needed with ratecontrol

Robert Swain robert.swain
Mon Sep 1 19:59:17 CEST 2008

2008/9/1 Kostya <kostya.shishkov at gmail.com>:
> As you may know, I'm working on AAC encoder.
> Today I've managed to add trellis-based scalefactor quantizer selection.
> While it looks like optimal selection (at least in terms of time spent
> on search :-S, but I'm pretty sure it's optimal except for quantization
> procedure itself), it depends on parameter lambda which I don't know
> how to control.
> Can somebody tell me how to manipulate lambda to achieve desired bitrate?
> I'm not sure I can use ratecontrol.c for that (it's too complex
> and mpegvideo-oriented).

I still maintain that a constant quality mode is important for the
success of a competitive transparent but lossy audio encoder. I don't
really know but I suspect that implementing this would not be too
difficult. However, it is useful if the quality scale is fairly linear
with bit rate which brings the 'issue' back around again.

This is, at least, how most other audio encoders work and offering
constant quality and bit rate methods for rate control seems to be a
good idea. :)


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