Support different RIDs per direction

src/change/sdp.rs

@@ -1081,8 +1081,14 @@ fn update_media(
         media.set_direction(new_dir);
     }
 
-    for rid in m.rids().iter() {
-        media.expect_rid_rx(*rid);
+    if new_dir.is_sending() {
+        // The other side has declared how it EXPECTING to receive. We must only send
+        // the RIDs declared in the answer.
+        media.set_rid_tx(m.rids().into());
+    }
+    if new_dir.is_receiving() {
+        // The other side has declared what it proposes to send. We are accepting it.
+        media.set_rid_rx(m.rids().into());
     }
 
     // Narrowing/ordering of of PT

src/media/mod.rs

@@ -49,6 +49,11 @@ pub struct Media {
     /// RTP level.
     rids_rx: Rids,
 
+    /// Rid that we can send using the [`Writer`].
+    ///
+    /// RTP level.
+    rids_tx: Rids,
+
     // ========================================= SDP level =========================================
     //
     /// The index of this media line in the Session::media Vec.
@@ -120,8 +125,10 @@ pub struct Media {
 }
 
 #[derive(Debug)]
-/// Config value for [`Media::rids_rx()`]
+/// Config value for [`Media::rids_rx()`] and [`Media::rids_tx()`]
 pub enum Rids {
+    /// No rid is allowed.
+    None,
     /// Any Rid is allowed.
     ///
     /// This is the default value for direct API.
@@ -135,6 +142,7 @@ pub enum Rids {
 impl Rids {
     pub(crate) fn contains(&self, rid: Rid) -> bool {
         match self {
+            Rids::None => false,
             Rids::Any => true,
             Rids::Specific(v) => v.contains(&rid),
         }
@@ -145,6 +153,12 @@ impl Rids {
     }
 }
 
+impl<I: AsRef<[Rid]>> From<I> for Rids {
+    fn from(value: I) -> Self {
+        Rids::Specific(value.as_ref().to_vec())
+    }
+}
+
 #[derive(Debug)]
 pub(crate) struct ToPayload {
     pub pt: Pt,
@@ -200,6 +214,16 @@ impl Media {
         &self.rids_rx
     }
 
+    /// Rids we are can send via the [`Writer`].
+    ///
+    /// By default this is set to [`Rids::None`], which changes to [`Rids::Specific`] via SDP negotiation
+    /// that configures Simulcast where specific rids are expected.
+    ///
+    /// RTP level.
+    pub fn rids_tx(&self) -> &Rids {
+        &self.rids_tx
+    }
+
     pub(crate) fn index(&self) -> usize {
         self.index
     }
@@ -467,6 +491,14 @@ impl Media {
         // Simply remove the depayloader, it will be re-created on the next RTP packet.
         self.depayloaders.remove(&(payload_type, rid));
     }
+
+    pub(crate) fn set_rid_rx(&mut self, rids: Rids) {
+        self.rids_rx = rids;
+    }
+
+    pub(crate) fn set_rid_tx(&mut self, rids: Rids) {
+        self.rids_tx = rids;
+    }
 }
 
 impl Default for Media {
@@ -484,6 +516,7 @@ impl Default for Media {
             dir: Direction::SendRecv,
             simulcast: None,
             rids_rx: Rids::Any,
+            rids_tx: Rids::None,
             payloaders: HashMap::new(),
             depayloaders: HashMap::new(),
             to_payload: VecDeque::default(),