[FFmpeg-trac] #4805(undetermined:new): swscale does not process pixels when only color-matrix differs between input and output

FFmpeg trac at avcodec.org
Wed Aug 26 14:18:23 CEST 2015


#4805: swscale does not process pixels when only color-matrix differs between
input and output
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             Reporter:  rmk          |                    Owner:
                 Type:  enhancement  |                   Status:  new
             Priority:  normal       |                Component:
              Version:  unspecified  |  undetermined
             Keywords:               |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
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Comment (by rmk):

 Replying to [comment:2 heleppkes]:
 > We have the colormatrix filter for this kind of conversions.
 >
 > -vf colormatrix=src=bt709:dst=bt601

 I know but
 - it's GPL (in my case that means I cannot use it),
 - it's very limited as far as pixel format is concerned, compared to
 swscale
 - it's more limited as far as color space support is concerned, compared
 to swscale
 - it seems like a good idea to only do the maintenance for coefficients
 etc. in one place and since the swscale api contract (as well as the
 vf_scale options) seems well-suited for the task, it is probably
 surprising for users to find that the functionality is not in that place
 (although there might be reasons as far as code complexity is concerned,
 that I don't know, not really knowing the impl code)

 I can only guess that the reason the colormatrix filter is there, was that
 someone else ran into this limitation, maybe knew the colormatrix support
 from ffmbc and decided to rather port than tackle the more complex task of
 making swscale support it (which is completely legitimate, of course).

--
Ticket URL: <https://trac.ffmpeg.org/ticket/4805#comment:4>
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