lavu: Document the color properties enumeration values origin

libavutil/pixfmt.h

@@ -313,6 +313,7 @@ enum AVPixelFormat {
 
 /**
   * Chromaticity coordinates of the source primaries.
+  * These values match the ones defined by ISO/IEC 23001-8_2013 § 7.1.
   */
 enum AVColorPrimaries {
     AVCOL_PRI_RESERVED0   = 0,
@@ -336,6 +337,7 @@ enum AVColorPrimaries {
 
 /**
  * Color Transfer Characteristic.
+ * These values match the ones defined by ISO/IEC 23001-8_2013 § 7.2.
  */
 enum AVColorTransferCharacteristic {
     AVCOL_TRC_RESERVED0    = 0,
@@ -364,6 +366,7 @@ enum AVColorTransferCharacteristic {
 
 /**
  * YUV colorspace type.
+ * These values match the ones defined by ISO/IEC 23001-8_2013 § 7.3.
  */
 enum AVColorSpace {
     AVCOL_SPC_RGB         = 0,  ///< order of coefficients is actually GBR, also IEC 61966-2-1 (sRGB)