[MEncoder-users] Fwd: Questions on Mencoder performace

[Jeff Clagg]

On Wed, Jun 07, 2006 at 08:40:43AM -0700, Phil Ehrens wrote:
> Strange. I am getting no blockiness at all. I am using a target
> bitrate of 2400 kbps and seeing actual average bitrates as low
> as 800 kbps for very noisy material. For the very clean material
> with high action the average bitrate is 2400 kbps, and there is
> no blocking at all. Again, this is for 2-pass encodes. For single
> pass the image degrades rapidly above nr=200.
> 
> I wonder why we are seeing such different behaviour? Maybe nr
> interacts badly with some other options or filters? My tests
> are all dvd -> lavc mpeg4 with no resizing, just cropping.

Quick uneducated guess: nr has way less practical effect at higher
quantizers, since higher frequency coefficients were less likely to be
coded anyway (and that is where the noise is).