[FFmpeg-user] BGR24-YUV420-BGR24 conversion on raw video

[Timo S]

Hello.

I am tring to find an explanation on this peculiarity: 

1) Introduce a raw BGR24 avi video and transcode it to YUV420 using ffmpeg
-i rawinput.avi -vcodec rawvideo -pix_fmt yuv420p output.yuv
2) Transcode it back to BGR24 avi using ffmpeg -s 848x480 -i output.yuv
-vcodec rawvideo -pix_fmt bgr24 raw_decoded.avi
3) Compare PSNR, AbsDiff and UIQ results on the original rawinput.avi and
raw_decoded.avi

Results: Comparative PSNR, AbsDiff and UIQ measurements on Y-components
indicate that the raw_decoded.avi has changed (ie PSNR-Y way less than 100
dB). Change definitely should be expected on U and V components but I did
not expect any change on Y component.

Any ideas?



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