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

crates/wzp-video/src/videotoolbox.rs

@@ -0,0 +1,107 @@
+//! Apple VideoToolbox H.264 encoder / decoder (macOS only).
+
+use crate::decoder::VideoDecoder;
+use crate::encoder::{VideoEncoder, VideoError, VideoFrame};
+
+/// macOS VideoToolbox H.264 encoder.
+///
+/// Wraps `VTCompressionSession`.  Minimum viable: API compiles and is
+/// instantiable; full hardware encode/decode lands in a follow-up task.
+pub struct VideoToolboxEncoder {
+    width: u32,
+    height: u32,
+    bitrate_bps: u32,
+    force_keyframe: bool,
+}
+
+impl VideoToolboxEncoder {
+    /// Create a new encoder.
+    ///
+    /// * `width` / `height` — frame dimensions in pixels.
+    /// * `bitrate_bps` — target bitrate in bits per second.
+    pub fn new(width: u32, height: u32, bitrate_bps: u32) -> Result<Self, VideoError> {
+        Ok(Self {
+            width,
+            height,
+            bitrate_bps,
+            force_keyframe: false,
+        })
+    }
+}
+
+impl VideoEncoder for VideoToolboxEncoder {
+    fn encode(&mut self, _frame: &VideoFrame) -> Result<Vec<u8>, VideoError> {
+        // TODO(T4.2-MVP): Wire VTCompressionSession.
+        // For now return an empty AU so the API compiles and callers can
+        // integrate the shape.
+        Ok(Vec::new())
+    }
+
+    fn request_keyframe(&mut self) {
+        self.force_keyframe = true;
+    }
+
+    fn is_keyframe(&self, packet: &[u8]) -> bool {
+        if packet.is_empty() {
+            return false;
+        }
+        let nal_type = packet[0] & 0x1F;
+        // NAL type 5 = IDR slice (keyframe).
+        nal_type == 5
+    }
+}
+
+/// macOS VideoToolbox H.264 decoder.
+///
+/// Wraps `VTDecompressionSession`.  Minimum viable: API compiles and is
+/// instantiable.
+pub struct VideoToolboxDecoder {
+    width: u32,
+    height: u32,
+}
+
+impl VideoToolboxDecoder {
+    /// Create a new decoder.
+    pub fn new(width: u32, height: u32) -> Result<Self, VideoError> {
+        Ok(Self { width, height })
+    }
+}
+
+impl VideoDecoder for VideoToolboxDecoder {
+    fn decode(&mut self, _access_unit: &[u8]) -> Result<Option<VideoFrame>, VideoError> {
+        // TODO(T4.2-MVP): Wire VTDecompressionSession.
+        Ok(None)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn encoder_instantiates() {
+        let enc = VideoToolboxEncoder::new(1280, 720, 2_000_000);
+        assert!(enc.is_ok());
+    }
+
+    #[test]
+    fn decoder_instantiates() {
+        let dec = VideoToolboxDecoder::new(1280, 720);
+        assert!(dec.is_ok());
+    }
+
+    #[test]
+    fn is_keyframe_detects_idr() {
+        let enc = VideoToolboxEncoder::new(1280, 720, 2_000_000).unwrap();
+        assert!(enc.is_keyframe(&[0x65, 0x01, 0x02]));
+        assert!(!enc.is_keyframe(&[0x41, 0x01, 0x02]));
+    }
+
+    #[test]
+    fn request_keyframe_sets_flag() {
+        let mut enc = VideoToolboxEncoder::new(1280, 720, 2_000_000).unwrap();
+        assert!(!enc.force_keyframe);
+        enc.request_keyframe();
+        assert!(enc.force_keyframe);
+    }
+}