[FFmpeg-devel] [PATCH] RoQ video encoder (take 4)

Loren Merritt lorenm
Fri Jun 15 00:09:56 CEST 2007

On Thu, 14 Jun 2007, Eric Lasota wrote:
> By the way, why does the rate control target rate lambda instead of
> total distortion, since base distortion can vary and cause quality to
> shift while lambda remains the same?

Lambda (or equivalently, quantizer) is the only thing that a ratecontrol 
algorithm can decide. Distortion isn't known until after you encode the 
frame. Now, a ratecontrol algorithm could use some heuristic to guess a 
lambda that might provide a given distortion, rather than guess a lambda 
that might provide a given bitrate. The reason no such mode exists is 
that you haven't written it.

--Loren Merritt

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