[x264-devel] Re: [PATCH] PSNR averages

[Loren Merritt]

On Mon, 9 Aug 2004, [iso-8859-1] Måns Rullgård wrote:

> BTW, why is it that the PSNR for the U and V planes is considerably
> higher than the Y plane?

Short answer: U and V are compressed less (smaller DCT block size, lower
quantizer)
Rational: U and V are already downsampled to half-resolution in the input
colorspace (I420/YV12), so for a given percieved quality, they need less
distortion.

--Loren Merritt

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