[FFmpeg-trac] #5980(avfilter:new): vf_zscale.c missing "allow_approximate_gamma" parameter to libzimg

FFmpeg trac at avcodec.org
Sun Nov 27 01:02:24 EET 2016

#5980: vf_zscale.c missing "allow_approximate_gamma" parameter to libzimg
             Reporter:  lvml      |                     Type:  enhancement
               Status:  new       |                 Priority:  normal
            Component:  avfilter  |                  Version:  git-master
             Keywords:  zscale    |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
 The zscale filter has no option to choose the "allow_approximate_gamma"
 parameter, and by default that parameter is zero, causing excessively slow
 scaling, because for every pixel, transcendent math functions are invoked
 for certain transfer functions.

 IMHO, allow_approximate_gamma = 1 should be the default, it speeds up
 "zscale" by an order of magnitude without visible differences in the
 result, and inserting

 params.allow_approximate_gamma = 1;

 is enough to achieve this.

 Of course, a filter option to control this would be even better.

Ticket URL: <https://trac.ffmpeg.org/ticket/5980>
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