[FFmpeg-trac] #2452(undetermined:new): decoding yuv420p to rgb shifts luminance down

FFmpeg trac at avcodec.org
Sat Aug 3 18:47:52 CEST 2013

#2452: decoding yuv420p to rgb shifts luminance down
             Reporter:  burek        |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
              Version:  unspecified  |  undetermined
             Keywords:               |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0

Comment (by glopes):

 Yes, I didn't check the actual mpeg4 frames (sorry if I wasn't clear).

 What I did check was the raw grayscale pixel intensities of the data
 coming in through the camera ''before it was encoded'' and then compared
 it to the pixel intensities of the reconstructed frames ''after

 So if the previous gray encoder/decoder pair was buggy it's interesting
 why they allowed me to reconstruct the pixel intensities perfectly in the
 first place.

 As to the last question, I just checked and I can find values ranging from
 8-255 without much effort. Not sure if there's absolute zeros in there
 because of lighting conditions, but it definitely looks like I'm full
 range (which doesn't happen with this current version, where pixels
 everywhere from [8-14] get squashed to 0).

 Don't have access to the setup right now, will try to make do. If I manage
 to reproduce anything meaningful about encoder differences, I'll let you
 I'm still learning about pixel format specifications, but I guess what I
 mean to say is that somehow the bytes that were encoded in the file
 contain information about the correct pixel intensities. I just want to
 make sure I can read them back...

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2452#comment:10>
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