[Ffmpeg-devel] [PATCH] DV image quality improvement

Rich Felker dalias
Sat Feb 25 23:18:42 CET 2006

On Sat, Feb 25, 2006 at 09:59:32PM +0100, Christian Iversen wrote:
> On Saturday 25 February 2006 21:18, Dan Maas wrote:
> > The attached (very small) patch improves image quality from ffmpeg's
> > DV encoder, increasing PSNR by about 3dB on the BBC's test footage.
> Not at all commenting on the quality of the patch in question (which is 
> probably great), when are "we" (meaning "you" :-) going to stop using PSNR as 
> a quality measure? There is only a quite weak correlation between percieved 
> image quality and PSNR. 
> There are other quality measures available that will give much better results. 
> A difference of 3dB really proves very, very little about how good the result 
> looks. 

Umm, as much as PSNR sucks, 3dB is HUGE. In ffmpeg development, 0.1dB
improvement is even considered fairly good, provided there are no
visual problems. I agree that PSNR in general doesn't say much about
video quality, but once you fix your testing to a particular codec
(and thus a particular type of quantization/error) it's fairly well
correlated with overall quality, at least for single frames. Often
these 0.1-0.2dB improvements come with a perceptible visual
improvement. Rate control makes the whole topic much more complicated
of course, but that's mostly irrelevant with DV which is normally CBR.


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