Address review feedback on mdcv/clli parsing

Fix hex literal formatting in BoxType constants to use '_' separators,
and fix read_mdcv to correctly remap wire order G, B, R to struct
indices R[0], G[1], B[2] per ISO 14496-12.

Author: alastor0325

mp4parse/src/boxes.rs

@@ -123,8 +123,8 @@ box_database!(
     ItemPropertyContainerBox          0x6970_636f, // "ipco"
     ItemPropertyAssociationBox        0x6970_6d61, // "ipma"
     ColourInformationBox              0x636f_6c72, // "colr"
-    MasteringDisplayColourVolumeBox   0x6d646376, // "mdcv"
-    ContentLightLevelBox              0x636c6c69, // "clli"
+    MasteringDisplayColourVolumeBox   0x6d64_6376, // "mdcv"
+    ContentLightLevelBox              0x636c_6c69, // "clli"
     ImageSpatialExtentsProperty       0x6973_7065, // "ispe"
     PixelAspectRatioBox               0x7061_7370, // "pasp"
     PixelInformationBox               0x7069_7869, // "pixi"

mp4parse/src/lib.rs

@@ -1171,8 +1171,8 @@ pub enum VideoCodecSpecific {
 }
 
 /// Mastering display colour volume from an `mdcv` box (ISO 14496-12).
-/// Primary indices are R\[0\], G\[1\], B\[2\]. Raw fixed-point values: divide chromaticity
-/// values by 50000 and luminance values by 10000 to obtain physical units.
+/// Primary indices are R\[0\], G\[1\], B\[2\]. Divide chromaticity values by 50000
+/// and luminance values by 10000 to obtain physical units.
 #[derive(Debug, Clone)]
 pub struct MasteringDisplayColourVolume {
     pub display_primaries_x: [u16; 3],
@@ -3731,8 +3731,12 @@ fn read_pasp<T: Read>(src: &mut BMFFBox<T>) -> Result<PixelAspectRatio> {
 
 /// Parse mastering display colour volume box (ISO 14496-12).
 fn read_mdcv<T: Read>(src: &mut BMFFBox<T>) -> Result<MasteringDisplayColourVolume> {
-    let display_primaries_x = [be_u16(src)?, be_u16(src)?, be_u16(src)?];
-    let display_primaries_y = [be_u16(src)?, be_u16(src)?, be_u16(src)?];
+    // Wire order is G, B, R (per ISO 14496-12); remap to R[0], G[1], B[2].
+    let (gx, gy) = (be_u16(src)?, be_u16(src)?);
+    let (bx, by) = (be_u16(src)?, be_u16(src)?);
+    let (rx, ry) = (be_u16(src)?, be_u16(src)?);
+    let display_primaries_x = [rx, gx, bx];
+    let display_primaries_y = [ry, gy, by];
     let white_point_x = be_u16(src)?;
     let white_point_y = be_u16(src)?;
     let max_display_mastering_luminance = be_u32(src)?;

mp4parse/src/tests.rs

@@ -1392,17 +1392,16 @@ fn read_to_end_oom() {
 
 #[test]
 fn read_mdcv() {
-    // Synthetic mdcv box: 3 primaries (R, G, B) x/y as u16, white point x/y,
-    // max/min luminance as u32. Values chosen to be distinct and easy to verify.
+    // Synthetic mdcv box. Wire order is G, B, R (x then y for each primary),
+    // remapped by read_mdcv to struct indices R[0], G[1], B[2].
     let mut stream = make_box(BoxSize::Auto, b"mdcv", |s| {
-        s // display_primaries_x[0..2] (R, G, B)
-            .B16(35400)
-            .B16(14600)
-            .B16(7500)
-            // display_primaries_y[0..2] (R, G, B)
-            .B16(14600)
-            .B16(59210)
-            .B16(3000)
+        s // Gx, Gy, Bx, By, Rx, Ry (wire order)
+            .B16(14600) // Gx
+            .B16(59210) // Gy
+            .B16(7500) // Bx
+            .B16(3000) // By
+            .B16(35400) // Rx
+            .B16(14600) // Ry
             // white_point_x, white_point_y
             .B16(15635)
             .B16(16450)