T4.2: VideoToolbox H.264 encoder/decoder traits (macOS, MVP)

crates/wzp-video/src/decoder.rs

@@ -0,0 +1,15 @@
+//! Video decoder trait and platform implementations.
+
+use crate::encoder::{VideoError, VideoFrame};
+
+/// Trait for video decoders.
+///
+/// Implementations are platform-specific (VideoToolbox on macOS, MediaCodec on
+/// Android, OpenH264 as software fallback).
+pub trait VideoDecoder: Send {
+    /// Decode one H.264 access unit into a raw video frame.
+    ///
+    /// Returns `Ok(Some(frame))` when a frame is ready, `Ok(None)` if more
+    /// data is needed (e.g., for reordering), or an error.
+    fn decode(&mut self, access_unit: &[u8]) -> Result<Option<VideoFrame>, VideoError>;
+}