T4.1: wzp-video crate scaffold + H.264 NAL framer + depacketizer

crates/wzp-video/src/lib.rs

@@ -0,0 +1,73 @@
+//! WZP video pipeline — H.264 baseline framer and depacketizer.
+//!
+//! This crate lives alongside `wzp-codec` and handles video-specific
+//! packetization (NAL fragmentation / reassembly).  Platform encoders and
+//! decoders land in T4.2/T4.3.
+
+pub mod depacketizer;
+pub mod framer;
+
+pub use depacketizer::H264Depacketizer;
+pub use framer::{FramedPacket, H264Framer};
+
+#[cfg(test)]
+mod tests {
+    use crate::{H264Depacketizer, H264Framer};
+
+    /// Build a synthetic H.264 access unit (Annex-B, 3-byte start codes):
+    /// - NAL 1: IDR slice (type 5) with 100-byte payload
+    /// - NAL 2: non-IDR slice (type 1) with 50-byte payload
+    fn synthetic_access_unit() -> Vec<u8> {
+        let mut au = Vec::new();
+        au.extend_from_slice(&[0x00, 0x00, 0x01, 0x65]); // IDR start code
+        au.extend_from_slice(&[0xCC; 100]);
+        au.extend_from_slice(&[0x00, 0x00, 0x01, 0x41]); // non-IDR start code
+        au.extend_from_slice(&[0xDD; 50]);
+        au
+    }
+
+    #[test]
+    fn roundtrip_single_nal() {
+        let au = synthetic_access_unit();
+        let framer = H264Framer::new(500);
+        let packets = framer.frame(&au);
+
+        let mut dep = H264Depacketizer::new();
+        let mut result = None;
+        for pkt in &packets {
+            result = dep.push(&pkt.payload, pkt.is_frame_end);
+        }
+
+        assert_eq!(result, Some(au));
+    }
+
+    #[test]
+    fn roundtrip_with_fu_a_fragmentation() {
+        let au = synthetic_access_unit();
+        // Max payload 30 bytes forces the 100-byte NAL into FU-A fragments.
+        let framer = H264Framer::new(30);
+        let packets = framer.frame(&au);
+
+        // The 100-byte NAL (1 header + 100 payload = 101 bytes) will be
+        // fragmented. 30-byte max means 28 bytes of data per fragment
+        // (2 bytes FU-A header).  100 payload bytes → 4 fragments.
+        // The 50-byte NAL (1 + 50 = 51) also fragments → 2 fragments.
+        // Total packets = 4 + 2 = 6.
+        assert_eq!(packets.len(), 6);
+
+        let mut dep = H264Depacketizer::new();
+        let mut result = None;
+        for pkt in &packets {
+            result = dep.push(&pkt.payload, pkt.is_frame_end);
+        }
+
+        assert_eq!(result, Some(au));
+    }
+
+    #[test]
+    fn roundtrip_empty_access_unit() {
+        let framer = H264Framer::new(100);
+        let packets = framer.frame(&[]);
+        assert!(packets.is_empty());
+    }
+}