T1.2: Add MediaType enum

crates/wzp-proto/src/lib.rs

@@ -17,6 +17,7 @@ pub mod codec_id;
 pub mod dred_tuner;
 pub mod error;
 pub mod jitter;
+pub mod media_type;
 pub mod packet;
 pub mod quality;
 pub mod session;
@@ -27,6 +28,7 @@ pub use bandwidth::{BandwidthEstimator, CongestionState};
 pub use codec_id::{CodecId, QualityProfile};
 pub use dred_tuner::{DredTuner, DredTuning};
 pub use error::*;
+pub use media_type::MediaType;
 pub use packet::{
     CallAcceptMode, FRAME_TYPE_FULL, FRAME_TYPE_MINI, HangupReason, MediaHeader, MediaHeaderV1,
     MediaHeaderV2, MediaPacket, MiniFrameContext, MiniHeader, PresenceUser, QualityReport,

crates/wzp-proto/src/media_type.rs

@@ -0,0 +1,51 @@
+use serde::{Deserialize, Serialize};
+
+/// Media stream type carried in a v2 [`MediaHeader`](crate::MediaHeaderV2).
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[repr(u8)]
+pub enum MediaType {
+    Audio = 0,
+    Video = 1,
+    Data = 2,
+    Control = 3,
+}
+
+impl MediaType {
+    pub const fn to_wire(self) -> u8 {
+        self as u8
+    }
+
+    pub const fn from_wire(v: u8) -> Option<Self> {
+        match v {
+            0 => Some(Self::Audio),
+            1 => Some(Self::Video),
+            2 => Some(Self::Data),
+            3 => Some(Self::Control),
+            _ => None,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn media_type_roundtrip() {
+        for mt in [
+            MediaType::Audio,
+            MediaType::Video,
+            MediaType::Data,
+            MediaType::Control,
+        ] {
+            assert_eq!(MediaType::from_wire(mt.to_wire()), Some(mt));
+        }
+    }
+
+    #[test]
+    fn media_type_unknown_rejected() {
+        for v in 4u8..=255 {
+            assert!(MediaType::from_wire(v).is_none(), "v={v}");
+        }
+    }
+}

crates/wzp-proto/src/packet.rs

@@ -1,7 +1,7 @@
 use bytes::{Buf, BufMut, Bytes, BytesMut};
 use serde::{Deserialize, Serialize};
 
-use crate::CodecId;
+use crate::{CodecId, MediaType};
 
 /// 12-byte v1 media packet header for the lossy link.
 ///
@@ -163,9 +163,9 @@ pub type MediaHeader = MediaHeaderV1;
 /// 16-byte v2 media header. See docs/PRD/PRD-wire-format-v2.md.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub struct MediaHeaderV2 {
-    pub version: u8,    // always 2
-    pub flags: u8,      // bit 7 T, bit 6 Q, bit 5 KeyFrame, bit 4 FrameEnd
-    pub media_type: u8, // TODO(T1.2): replace with MediaType
+    pub version: u8, // always 2
+    pub flags: u8,   // bit 7 T, bit 6 Q, bit 5 KeyFrame, bit 4 FrameEnd
+    pub media_type: MediaType,
     pub codec_id: CodecId,
     pub stream_id: u8,
     pub fec_ratio: u8, // 0..200 -> 0.0..2.0
@@ -181,7 +181,7 @@ impl MediaHeaderV2 {
     pub fn write_to(&self, buf: &mut impl BufMut) {
         buf.put_u8(self.version);
         buf.put_u8(self.flags);
-        buf.put_u8(self.media_type);
+        buf.put_u8(self.media_type.to_wire());
         buf.put_u8(self.codec_id.to_wire());
         buf.put_u8(self.stream_id);
         buf.put_u8(self.fec_ratio);
@@ -199,7 +199,7 @@ impl MediaHeaderV2 {
             return None;
         }
         let flags = buf.get_u8();
-        let media_type = buf.get_u8();
+        let media_type = MediaType::from_wire(buf.get_u8())?;
         let codec_id = CodecId::from_wire(buf.get_u8())?;
         let stream_id = buf.get_u8();
         let fec_ratio = buf.get_u8();
@@ -1289,7 +1289,7 @@ mod tests {
         let h = MediaHeaderV2 {
             version: 2,
             flags: MediaHeaderV2::FLAG_QUALITY,
-            media_type: 0, // TODO(T1.2): MediaType::Audio
+            media_type: MediaType::Audio,
             codec_id: CodecId::Opus24k,
             stream_id: 0,
             fec_ratio: 50,