[FFmpeg-trac] #3801(undetermined:new): SWSCALE: Incorrect Values in Full Range Conversion RGB to YCbCr

FFmpeg trac at avcodec.org
Thu Jul 24 20:12:33 CEST 2014

#3801: SWSCALE: Incorrect Values in Full Range Conversion RGB to YCbCr
             Reporter:  troy_s       |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
 Summary of the bug:

 FFMPEG is potentially delivering values that deviate from theoretical
 results in RGB to YCbCr conversions. This case applies to RGB to full
 range YCbCr conversion, using REC.709 coefficients on the input.

 ./ffmpeg -i ~/Documents/FFMPEG\ Color\ Research/ARIB_STD-B28.png -pix_fmt
 yuv444p -vcodec rawvideo -f rawvideo -vf
 ffmpeg version N-64958-gce8e27e Copyright (c) 2000-2014 the FFmpeg
   built on Jul 24 2014 10:54:07 with gcc 4.7 (Ubuntu/Linaro
   configuration: --enable-gpl --enable-libx264 --enable-shared --disable-
 static --enable-pic
   WARNING: library configuration mismatch
   avutil      configuration: --enable-gpl --enable-libx264 --disable-asm
 --enable-shared --disable-static --enable-pic
   avcodec     configuration: --enable-gpl --enable-libx264 --disable-asm
 --enable-shared --disable-static --enable-pic
   avformat    configuration: --enable-gpl --enable-libx264 --disable-asm
 --enable-shared --disable-static --enable-pic
   avdevice    configuration: --enable-gpl --enable-libx264 --disable-asm
 --enable-shared --disable-static --enable-pic
   avfilter    configuration: --enable-gpl --enable-libx264 --disable-asm
 --enable-shared --disable-static --enable-pic
   swscale     configuration: --enable-gpl --enable-libx264 --disable-asm
 --enable-shared --disable-static --enable-pic
   swresample  configuration: --enable-gpl --enable-libx264 --disable-asm
 --enable-shared --disable-static --enable-pic
   postproc    configuration: --enable-gpl --enable-libx264 --disable-asm
 --enable-shared --disable-static --enable-pic
   libavutil      52. 92.101 / 52. 92.101
   libavcodec     55. 69.100 / 55. 69.100
   libavformat    55. 49.100 / 55. 49.100
   libavdevice    55. 13.102 / 55. 13.102
   libavfilter     4. 11.102 /  4. 11.102
   libswscale      2.  6.100 /  2.  6.100
   libswresample   0. 19.100 /  0. 19.100
   libpostproc    52.  3.100 / 52.  3.100
 Input #0, image2, from '/home/aphorism/Documents/FFMPEG Color
   Duration: 00:00:00.04, start: 0.000000, bitrate: N/A
     Stream #0:0: Video: png, rgb24, 1920x1080 [SAR 2835:2835 DAR 16:9], 25
 tbr, 25 tbn, 25 tbc
 Output #0, rawvideo, to 'test-full.yuv':
     encoder         : Lavf55.49.100
     Stream #0:0: Video: rawvideo (444P / 0x50343434), yuv444p, 1920x1080
 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc
       encoder         : Lavc55.69.100 rawvideo
 Stream mapping:
   Stream #0:0 -> #0:0 (png (native) -> rawvideo (native))
 Press [q] to stop, [?] for help
 frame=    1 fps=0.0 q=0.0 Lsize=    6075kB time=00:00:00.04
 video:6075kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.000000%

 The above command delivers the attachment test-full-444-out.png, with Y,
 Cb, and Cr a pure dump of the results into the R, G, and B channels of the
 image. No color transformations have been applied.

 The file ARIB_STD-B28.png is an 8 bit representation of a SMPTE test
 pattern, based off of a 32 bit float version.

 The file ARIB_STD-B28_YCbCr_full.png is a theoretically correct
 transformation of the ARIB_STD-B28.png test pattern into YCbCr using
 REC.709 coefficients. It is based off of a 32 bit EXR input.

 The file test-full-diff.png is a heat-map difference, with red areas
 indicating deviations between the theoretical results and the actual.

 The SMPTE test pattern black set test stripes at the very bottom contain
 one stripe that sources at -2%, and as such, will always be incorrect
 unless float values are provided for input. As such, it is the single bar
 that can be ignored.

 Potentially Related Issues:

Ticket URL: <https://trac.ffmpeg.org/ticket/3801>
FFmpeg <https://ffmpeg.org>
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