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