meson: bump API for input ICC frame luminance fix

Now input frame.hdr.max_luma is now respected by when frame has ICC
profile. Previously regardless of max_luma value, if ICC profile was
attached, internally max_luma were always replaced by
PL_COLOR_SDR_WHITE. That's no longer the case and you can render SDR at
any requested luminance level, for example when doing SDR->PQ
conversion. There is no behaviour change when input max_luma==0, in
which case default PL_COLOR_SDR_WHITE will be used.

Note that by design we never use ICC reported luminance for SDR content,
as we render by default at PL_COLOR_SDR_WHITE (203) nits or at level
requested in max_luma filed.

This was changed in 50a7571 and
subsequently adjusted in next commits, to avoid SDR->SDR luminance
mismatch.

This API bump is to allow users decide if this fix is present and it
can be used. For example in mpv we need to know if libplecebo will
respect max_luma or use 203 nits.

Author: kasper93

meson.build

@@ -12,6 +12,7 @@ project('libplacebo', ['c', 'cpp'],
     7,
     # API version
     {
+      '371': 'input frame.hdr.max_luma is now respecte when frame has ICC profile',
       '370': 'deprecate pl_avdovi_metadata_supported and pl_avframe_params.map_dovi_force',
       '369': 'add pl_color_decode_args.enhancement_layer',
       '368': 'add pl_shader_decode_color_ex and pl_color_decode_args, deprecate pl_shader_decode_color',

src/colorspace.c

@@ -975,7 +975,7 @@ void pl_color_space_infer_map(struct pl_color_space *src,
     if (unknown_src_luminance && src_is_sdr && dst_is_sdr)
         src->hdr.max_luma = dst->hdr.max_luma;
 
-    // If SDR source has luminance, say from ICC profile, use it for target.
+    // If SDR source has luminance, use it for target.
     if (!unknown_src_luminance && src_is_sdr && dst_is_sdr)
         dst->hdr.max_luma = src->hdr.max_luma;