From 7c93401f7d76bffce49f1a6b49babc70864c449d Mon Sep 17 00:00:00 2001
From: Alastor Wu <alwu@mozilla.com>
Date: Wed, 3 Jun 2026 14:23:52 -0700
Subject: [PATCH] Accept multiple colr boxes in a video sample entry
MIME-Version: 1.0
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ISO/IEC 14496-12:2015 § 12.1.5.1 permits one or more ColourInformationBoxes
in a VisualSampleEntry and assigns them no normative behaviour; a reader may
keep the first (most accurate) box and ignore the rest. Rejecting a sample
entry that carries a second colr box therefore breaks valid files, such as
the backward-compatible HLG dual-colr signaling convention.

Demote the duplicate-colr case from a hard parse error under Normal strictness
to warn-and-keep-first, rejecting only under Strict. The first box's CICP data
is still surfaced unchanged.
---
 mp4parse/src/lib.rs                           |   6 +++-
 mp4parse_capi/tests/test_colour_info.rs       |  26 ++++++++++++++++++
 .../tests/video_colr_nclx_two_colr.mp4        | Bin 0 -> 1685 bytes
 3 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 mp4parse_capi/tests/video_colr_nclx_two_colr.mp4

diff --git a/mp4parse/src/lib.rs b/mp4parse/src/lib.rs
index 955e902f..6a404556 100644
--- a/mp4parse/src/lib.rs
+++ b/mp4parse/src/lib.rs
@@ -5772,9 +5772,13 @@ fn read_video_sample_entry<T: Read>(
             }
             BoxType::ColourInformationBox => {
                 if colour_info.is_some() {
+                    // ISO/IEC 14496-12:2015 § 12.1.5.1 permits one or more colr boxes
+                    // in a VisualSampleEntry and assigns them no normative behaviour;
+                    // a reader may keep the first (most accurate) and ignore the rest.
+                    // Only reject under Strict.
                     warn!("Multiple colr boxes in video sample entry, keeping first");
                     fail_with_status_if(
-                        strictness != ParseStrictness::Permissive,
+                        strictness == ParseStrictness::Strict,
                         Status::ColrBadQuantityBMFF,
                     )?;
                     skip_box_content(&mut b)?;
diff --git a/mp4parse_capi/tests/test_colour_info.rs b/mp4parse_capi/tests/test_colour_info.rs
index 3d0312d1..eaed00e7 100644
--- a/mp4parse_capi/tests/test_colour_info.rs
+++ b/mp4parse_capi/tests/test_colour_info.rs
@@ -135,6 +135,32 @@ fn video_colr_nclx_rgb_identity_matrix() {
     }
 }
 
+/// Two adjacent nclx colr boxes in one video sample entry (the backward-compatible
+/// HLG signaling convention). ISO/IEC 14496-12:2015 § 12.1.5.1 permits "one or more"
+/// ColourInformationBoxes and assigns them no normative behaviour; the reader keeps the
+/// first (most accurate) box. The parse must succeed and surface the first box (HLG,
+/// transfer=18), not the second (transfer=14).
+#[test]
+fn video_colr_nclx_two_colr() {
+    unsafe {
+        let parser = open_parser("tests/video_colr_nclx_two_colr.mp4");
+
+        let mut video = Mp4parseTrackVideoInfo::default();
+        let rv = mp4parse_get_track_video_info(parser, 0, &mut video);
+        assert_eq!(rv, Mp4parseStatus::Ok);
+
+        assert_eq!(video.sample_info_count, 1);
+        let sample = &*video.sample_info;
+        assert!(sample.has_colour_info);
+        assert_eq!(sample.colour_primaries, 9);
+        assert_eq!(sample.transfer_characteristics, 18); // first box (HLG) wins
+        assert_eq!(sample.matrix_coefficients, 9);
+        assert!(!sample.full_range_flag);
+
+        mp4parse_free(parser);
+    }
+}
+
 /// No colr box: has_colour_info=false, CICP fields are zero
 #[test]
 fn video_no_colr_box() {
diff --git a/mp4parse_capi/tests/video_colr_nclx_two_colr.mp4 b/mp4parse_capi/tests/video_colr_nclx_two_colr.mp4
new file mode 100644
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