[FFmpeg-devel] [PATCH]Sanitize VBR setting for libfdk-aac

Michael Niedermayer michaelni at gmx.at
Thu Sep 13 03:24:01 CEST 2012

On Wed, Sep 12, 2012 at 05:50:01PM -0400, Derek Buitenhuis wrote:
> On 12/09/2012 5:33 PM, Carl Eugen Hoyos wrote:
> > This is insane.
> It's a lot more sane than passing through a stupid legacy constant that is related to...
> what is it... MPEG-1/2/4? It has no business here, and only serves to make code
> convoluted, and propagate a cargo culted method of coding from the Bad Old Days (2003?).

The qscale and (global) quality fields are rate distortion coeffs,
normally the letter lambda is used for them.
What they really are is simply a value that says how many bits are
equivalent to a unit change in quality, where quality can be anything
from "PSNR" to some psyco vissual thing in theory.

i suspect using this field for the fdk-aac encoder here is incorrect.
But i must admit i have difficulty matching anything up with
"cargo culted methods of the bad old days".

> However, rather than argue about it, and try and shoehorn it into this option, I think
> a codec private option would be far more sane. The original author agrees. I can send a
> patch for this.

i agree on that part

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Concerning the gods, I have no means of knowing whether they exist or not
or of what sort they may be, because of the obscurity of the subject, and
the brevity of human life -- Protagoras
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