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

crates/wzp-video/src/encoder.rs

@@ -0,0 +1,65 @@
+//! Video encoder trait and platform implementations.
+
+/// Errors that can occur during video encoding or decoding.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum VideoError {
+    /// Platform codec failed (e.g., VTCompressionSession error).
+    PlatformError(String),
+    /// Invalid input parameters.
+    InvalidInput(String),
+    /// Codec is not initialized.
+    NotInitialized,
+}
+
+impl std::fmt::Display for VideoError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            VideoError::PlatformError(s) => write!(f, "platform error: {s}"),
+            VideoError::InvalidInput(s) => write!(f, "invalid input: {s}"),
+            VideoError::NotInitialized => write!(f, "codec not initialized"),
+        }
+    }
+}
+
+impl std::error::Error for VideoError {}
+
+/// Trait for video encoders.
+///
+/// Implementations are platform-specific (VideoToolbox on macOS, MediaCodec on
+/// Android, OpenH264 as software fallback).
+pub trait VideoEncoder: Send {
+    /// Encode one raw video frame into a H.264 access unit.
+    ///
+    /// Returns the encoded bytes (one complete access unit) or an error.
+    fn encode(&mut self, frame: &VideoFrame) -> Result<Vec<u8>, VideoError>;
+
+    /// Request the next encoded frame to be an I-frame (keyframe).
+    fn request_keyframe(&mut self);
+
+    /// Returns true if the given encoded packet is a keyframe.
+    fn is_keyframe(&self, packet: &[u8]) -> bool;
+}
+
+/// Raw video frame input for encoding.
+#[derive(Clone, Debug)]
+pub struct VideoFrame {
+    /// Width in pixels.
+    pub width: u32,
+    /// Height in pixels.
+    pub height: u32,
+    /// Pixel data (NV12 or I420, depending on platform).
+    pub data: Vec<u8>,
+    /// Presentation timestamp in milliseconds.
+    pub timestamp_ms: u64,
+}
+
+impl VideoFrame {
+    pub fn new(width: u32, height: u32, data: Vec<u8>, timestamp_ms: u64) -> Self {
+        Self {
+            width,
+            height,
+            data,
+            timestamp_ms,
+        }
+    }
+}