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

FFmpeg trac at avcodec.org
Sat Aug 3 16:34:55 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):

 Thanks for the reference. I have to admit I'm not entirely sure I
 understand what the problem was with encoding gray input...

 More importantly, did the fix change anything about the way gray format is

 The video was produced using the AForge framework, which underneath uses
 some version of FFMPEG prior to 2012. I did not reencode the video with
 the new version, nor would I want to, since I have 1.5 years of these
 videos to analyze that just can't be reencoded...

 In my case, it turns out I am absolutely sure that the gray encoding is
 actually correct, since I checked the frame grabber's pixel values myself
 in real-time while the data was coming through precisely to make sure that
 it wasn't an encoder problem, back when I found out about this.

 This decoding issue now places me at risk of either losing data since the
 shift actually reduces precious contrast or having to stop updating FFMPEG
 from now on; neither of them I am particularly fond of...

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2452#comment:7>
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