[Ffmpeg-devel] Discrete levels on image quality
jean.mab at bluewin.ch
Tue Jan 30 09:55:48 CET 2007
I want to modify the quality compression of an image while using a
mpeg4 video compression.
Here is what I have done:
c->flags=CODEC_FLAG_QSCALE;// enable quality compression
I found that it's possible to change the quality between 1 (good)
and FF_LAMBDA_MAX (bad) where FF_LAMBDA_MAX =256*128-1.
After some experiments, it seems that there are 29 steps between
these values making changing the quality. These steps are:
That is the reason why these commands are the same:
> picture->quality=100; (Not change image).
> picture->quality=50; (Not change image).
> picture->quality=1; (Not change image).
Does somebody explain me a little more about these steps?
I thought that image->quality changes the quality factor of the
jpeg compression but it doesn't seem to be that.
Does somebody know on which level does this quality act?
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