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

FFmpeg trac at avcodec.org
Fri May 9 19:59:28 CEST 2014

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

Comment (by andreasg):

 I verified that the values in frame->data[0] and gray_frame->data[0] are
 the same when considering the respective linesize[0].  Thus, the fast
 version produces correct output.

 As ff_get_unscaled_swscale only sets swscale if it can handle the
 transformation, it might be possible to simplify the test above to the

 if (unscaled && !usesHFilter && !usesVFilter) {

 planarCopyWrapper in swscale_unscaled.c seems to do a fine and fast job in
 this situation.

Ticket URL: <https://trac.ffmpeg.org/ticket/3625#comment:4>
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