From 8469229647468f339bf90ced80459a7b1add5fdd Mon Sep 17 00:00:00 2001
From: Philippe Normand <philn@igalia.com>
Date: Fri, 29 Mar 2024 13:57:31 +0000
Subject: [PATCH] Add API for ChromaLocation information retrieval

---
 src/lib.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index 556b9e7..b3868db 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -729,6 +729,18 @@ impl Picture {
             }
         }
     }
+
+    /// Sample position for subsampled chroma.
+    pub fn chroma_location(&self) -> pixel::ChromaLocation {
+        // According to y4m mapping declared in dav1d's output/y4m2.c and applied from FFmpeg's yuv4mpegdec.c
+        unsafe {
+            match (*self.inner.pic.seq_hdr).chr {
+                DAV1D_CHR_UNKNOWN | DAV1D_CHR_COLOCATED => pixel::ChromaLocation::Center,
+                DAV1D_CHR_VERTICAL => pixel::ChromaLocation::Left,
+                _ => unreachable!(),
+            }
+        }
+    }
 }
 
 static_assertions::assert_impl_all!(Picture: Send, Sync);