[FFmpeg-trac] #10136(swscale:new): Can't convert color range with sws_scale

[FFmpeg]

#10136: Can't convert color range with sws_scale
---------------------------------+--------------------------------------
             Reporter:  diogo.r  |                     Type:  defect
               Status:  new      |                 Priority:  normal
            Component:  swscale  |                  Version:  git-master
             Keywords:           |               Blocked By:
             Blocking:           |  Reproduced by developer:  0
Analyzed by developer:  0        |
---------------------------------+--------------------------------------
 Summary of the bug:
 I'm trying to convert a frame with sws_scale while selecting the color
 range of the input and output, but for some input formats it doesn't work,
 it ignores the color ranges I set. I looked into it and found weird this
 check in 'libswscale/utils.c:1046':

 {{{
     //The srcBpc check is possibly wrong but we seem to lack a definitive
 reference to test this
     //and what we have in ticket 2939 looks better with this check
     if (need_reinit && (c->srcBpc == 8 || !isYUV(c->srcFormat)))
         ff_sws_init_range_convert(c);
 }}}

 I looked at ticket 2939, but didn't find reasoning about why the
 {{{(c->srcBpc == 8 || !isYUV(c->srcFormat)}}} check is necessary.

 How to reproduce:
 {{{


 extern "C"
 {
         #include <libswscale/swscale.h>
 }
 #include "assert.h"

 int main() {
         AVPixelFormat in_pix_fmt = AVPixelFormat::AV_PIX_FMT_YUV420P10LE;
         AVPixelFormat out_pix_fmt = AVPixelFormat::AV_PIX_FMT_YUV420P;
         int width = 32;
         int height = 32;

         SwsContext *sws_ctx = (struct SwsContext*)sws_getContext(
                 width,
                 height,
                 in_pix_fmt,
                 width,
                 height,
                 out_pix_fmt,
                 SWS_BILINEAR,
                 NULL,
                 NULL,
                 NULL
         );

         int *table = NULL;
         int *inv_table = NULL;
         int srcRange = -1;
         int dstRange = -1;
         int brightness = -1;
         int contrast = -1;
         int saturation = -1;

         int res = sws_getColorspaceDetails(
                 sws_ctx,
                 &inv_table,
                 &srcRange,
                 &table,
                 &dstRange,
                 &brightness,
                 &contrast,
                 &saturation
         );
         assert(res == 0);

         printf(
                 R"(
         srcRange        = %d
         dstRange        = %d
         brightness      = %d
         contrast        = %d
         saturation      = %d
         table           = [%d, %d, %d, %d]
         inv_table       = [%d, %d, %d, %d]
 )",
                 srcRange,
                 dstRange,
                 brightness,
                 contrast,
                 saturation,
                 table[0],
                 table[1],
                 table[2],
                 table[3],
                 inv_table[0],
                 inv_table[1],
                 inv_table[2],
                 inv_table[3]
         );

         srcRange = 1;

         res = sws_setColorspaceDetails(
                 sws_ctx,
                 inv_table,
                 srcRange,
                 table,
                 dstRange,
                 brightness,
                 contrast,
                 saturation
         );

         // Do the conversion
         // sws_scale(...)

         assert(res == 0);
         return 0;
 }
 }}}
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10136>
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