Correctly handle per m-line Absolute Send Time

CHANGELOG.md

@@ -11,6 +11,7 @@
   * Fix RTX stops working after packet loss spike #566
   * Configure RTX ratio cap via `StreamTx::set_rtx_cache` #570
   * Correctly handle per m-line TWCC #573
+  * Correctly handle per m-line Absolute Send Time #575
 
 # 0.6.1
   * Force openssl to be >=0.10.66 #545

src/streams/send.rs

@@ -14,8 +14,8 @@ use crate::media::MediaKind;
 use crate::packet::QueuePriority;
 use crate::packet::QueueSnapshot;
 use crate::packet::QueueState;
-use crate::rtp_::Bitrate;
 use crate::rtp_::{extend_u16, Descriptions, ReportList, Rtcp};
+use crate::rtp_::{Bitrate, Extension};
 use crate::rtp_::{ExtensionMap, ReceptionReport, RtpHeader};
 use crate::rtp_::{ExtensionValues, Frequency, MediaTime, Mid, NackEntry};
 use crate::rtp_::{Pt, Rid, RtcpFb, SenderInfo, SenderReport, Ssrc};
@@ -465,7 +465,11 @@ impl StreamTx {
 
         // These need to match `Extension::is_supported()` so we are sending what we are
         // declaring we support.
-        header.ext_vals.abs_send_time = Some(now);
+
+        // Absolute Send Time might not be enabled for this m-line.
+        if exts.id_of(Extension::AbsoluteSendTime).is_some() {
+            header.ext_vals.abs_send_time = Some(now);
+        }
 
         // TWCC might not be enabled for this m-line.
         if let Some(twcc) = twcc {