When I measure the PSNR of the separate Y,U,V components, I notice a significantly higher PSNR for the color components whereas I would expect an equal or even slightly less PSNR for the color. Can anybody explain this?
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Actually that's pretty normal - and you see the same thing on the h264 reference encoder. The reason is that the colour components tend to be naturally much more band-limited than the luminance, and so the encoder preserves them more easily - giving the high PSNR.
Since the colour components are so band-limited, if you let the encoder push the bitrate, then you risk the colour being quantised away completely leaving a black and white picture. Since colour components are only 5-10% of the bitrate anyway it's best to err on the side of caution and let the quality be higher.
regards
Thomas
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When I measure the PSNR of the separate Y,U,V components, I notice a significantly higher PSNR for the color components whereas I would expect an equal or even slightly less PSNR for the color. Can anybody explain this?
Actually that's pretty normal - and you see the same thing on the h264 reference encoder. The reason is that the colour components tend to be naturally much more band-limited than the luminance, and so the encoder preserves them more easily - giving the high PSNR.
Since the colour components are so band-limited, if you let the encoder push the bitrate, then you risk the colour being quantised away completely leaving a black and white picture. Since colour components are only 5-10% of the bitrate anyway it's best to err on the side of caution and let the quality be higher.
regards
Thomas
Thanks Thomas, your answer sound plausible. At first sight I expected differently, since the human visual system is less sensitive for color.
Grt,
Egbert Jaspers