Add some comments.

diff --git a/src/lib/image.cc b/src/lib/image.cc
index 41582f307b30b23bce02603aad7c9f74bae1f6f0..46c085ff2cf17943b6bd3b2b11d90779fefdfefc 100644 (file)
--- a/src/lib/image.cc
+++ b/src/lib/image.cc
@@ -185,6 +185,18 @@ Image::crop_scale_window (
                SWS_CS_ITU709
        };
 
+       /* The 3rd parameter here is:
+          0 -> source range MPEG (i.e. "video", 16-235)
+          1 -> source range JPEG (i.e. "full", 0-255)
+          And the 5th:
+          0 -> destination range MPEG (i.e. "video", 16-235)
+          1 -> destination range JPEG (i.e. "full", 0-255)
+
+          But remember: sws_setColorspaceDetails ignores
+          these parameters unless the image isYUV or isGray
+          (if it's neither, it uses video range for source
+          and destination).
+       */
        sws_setColorspaceDetails (
                scale_context,
                sws_getCoefficients (lut[yuv_to_rgb]), 0,
@@ -271,6 +283,18 @@ Image::scale (dcp::Size out_size, dcp::YUVToRGB yuv_to_rgb, AVPixelFormat out_fo
                SWS_CS_ITU709
        };
 
+       /* The 3rd parameter here is:
+          0 -> source range MPEG (i.e. "video", 16-235)
+          1 -> source range JPEG (i.e. "full", 0-255)
+          And the 5th:
+          0 -> destination range MPEG (i.e. "video", 16-235)
+          1 -> destination range JPEG (i.e. "full", 0-255)
+
+          But remember: sws_setColorspaceDetails ignores
+          these parameters unless the image isYUV or isGray
+          (if it's neither, it uses video range for source
+          and destination).
+       */
        sws_setColorspaceDetails (
                scale_context,
                sws_getCoefficients (lut[yuv_to_rgb]), 0,