[FFmpeg-trac] #3625(swscale:closed): Unscaled conversion from yuv420p to gray is slow

[FFmpeg]

#3625: Unscaled conversion from yuv420p to gray is slow
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             Reporter:  andreasg    |                    Owner:
                 Type:  defect      |                   Status:  closed
             Priority:  normal      |                Component:  swscale
              Version:  git-master  |               Resolution:  worksforme
             Keywords:              |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
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Changes (by cehoyos):

 * status:  new => closed
 * resolution:   => worksforme


Comment:

 The original behaviour was buggy (and was fixed), it produced gray output
 both for white and black input.
 There are now at least four possibilities to get the "old" behaviour for a
 "conversion" from yuv420p to gray:
 * Use frame->data[0] instead of involving libswscale at all (this is at
 least a nuance faster than the "old" behaviour)
 * Force yuvj420p as input colour space for libswscale (this option is
 deprecated)
 * Force the needed input color_range when using libswscale
 * Use the extractplanes filter

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Ticket URL: <https://trac.ffmpeg.org/ticket/3625#comment:12>
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