[MPlayer-users] PSNR Question Completed!
Struan Bartlett
struan at NewsNow.co.uk
Fri Feb 14 23:26:34 CET 2003
Sorry 'bout my previous incomplete email (sent by a rogue keypress).
I'm comparing the PSNRs generated with different lavcopts when encoding
a 60s chunk of a DVD.
I don't understand why the PSNR *decreases* when I crop the black
borders surrounding the picture. I would have expected that, following
the crop, for a given bitrate the PSNR would increase, as there would be
available more bits per pixel.
-oac copy -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=10000:psnr:vhq:vpass=1
Pos: 60.0s 1500f (99%) 14fps Trem: 0min 19mb A-V:0.040 [2217:448]
Video stream: 2217.400 kbit/s (277174 bps) size: 16619410 bytes 59.960
secs 1500 frames
Audio stream: 448.000 kbit/s (56000 bps) size: 3388000 bytes 60.500 secs
PSNR: Y:48.18, Cb:49.54, Cr:50.71, All:48.73
But:
-oac copy -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=10000:psnr:vpass=1:vhq
-vop crop=720:426:0:74
Pos: 60.0s 1500f (99%) 14fps Trem: 0min 18mb A-V:0.040 [2152:448]
Video stream: 2152.284 kbit/s (269035 bps) size: 16131372 bytes 59.960
secs 1500 frames
Audio stream: 448.000 kbit/s (56000 bps) size: 3388000 bytes 60.500 secs
PSNR: Y:46.54, Cb:48.19, Cr:49.34, All:47.15
Please can anyone explain why this might be?
Struan.
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