feat(video-streamer): add periodic keyframe forcing for improved seekability

crates/video-streamer/src/streamer/mod.rs

@@ -220,8 +220,10 @@ pub fn webm_stream(
                 }
             }
         });
-        // If the oneshot sender is dropped (task panicked), treat as Break
-        rx.blocking_recv().unwrap_or(WhenEofControlFlow::Break)
+        rx.blocking_recv().unwrap_or_else(|_| {
+            warn!("when_eof oneshot sender dropped unexpectedly, treating as shutdown");
+            WhenEofControlFlow::Break
+        })
     }
 
     enum WhenEofControlFlow {

crates/video-streamer/src/streamer/tag_writers.rs

@@ -20,6 +20,10 @@ const VPX_EFLAG_FORCE_KF: u32 = 0x00000001;
 /// - 0 = never skip (disables adaptive skipping effectively)
 const MAX_CONSECUTIVE_FRAME_SKIPS: u32 = 1;
 
+/// Interval in milliseconds at which keyframes are forced in the outgoing stream.
+/// Periodic keyframes improve seekability and resilience to packet loss.
+const KEYFRAME_INTERVAL_MS: u64 = 10_000;
+
 #[cfg(feature = "perf-diagnostics")]
 fn duration_as_millis_u64(duration: Duration) -> u64 {
     u64::try_from(duration.as_millis()).unwrap_or(u64::MAX)
@@ -111,6 +115,7 @@ where
     codec: VpxCodec,
     cut_block_state: CutBlockState,
     last_encoded_abs_time: Option<u64>,
+    last_keyframe_abs_time: Option<u64>,
 
     // Adaptive frame skipping state
     #[cfg(feature = "perf-diagnostics")]
@@ -204,6 +209,7 @@ where
                 codec: config.codec,
                 cut_block_state: CutBlockState::HaventMet,
                 last_encoded_abs_time: None,
+                last_keyframe_abs_time: None,
                 #[cfg(feature = "perf-diagnostics")]
                 stream_start: Instant::now(),
                 processing_time: Duration::ZERO,
@@ -399,6 +405,13 @@ where
         }
     }
 
+    fn should_force_keyframe(&self, abs_time: u64) -> bool {
+        match self.last_keyframe_abs_time {
+            Some(last_kf_time) => abs_time.saturating_sub(last_kf_time) >= KEYFRAME_INTERVAL_MS,
+            None => false,
+        }
+    }
+
     fn should_skip_encode(&self) -> bool {
         // Skip encoding when falling behind real-time. The ratio naturally self-regulates:
         // skipping makes processing faster (decode-only), which pushes ratio back above 1.0,
@@ -484,6 +497,7 @@ where
                 perf_trace!(block_timestamp, "Writing block to output");
                 self.write_block(block)?;
                 self.last_encoded_abs_time = Some(abs_time);
+                self.last_keyframe_abs_time = Some(abs_time);
             }
             CutBlockState::Met {
                 cut_block_absolute_time,
@@ -513,8 +527,10 @@ where
                 );
                 self.frames_since_last_encode = 0;
 
+                let force_keyframe = self.should_force_keyframe(abs_time);
+
                 let duration = self.compute_encode_duration(abs_time);
-                let frame = self.reencode(current_video_block, false, duration)?;
+                let frame = self.reencode(current_video_block, force_keyframe, duration)?;
                 let Some(frame) = frame else {
                     perf_trace!(block_timestamp, "No frame available from encoder - skipping");
                     return Ok(());
@@ -524,10 +540,25 @@ where
                 let frame_size = frame.len();
                 perf_trace!(block_timestamp, frame_size, "Frame available from encoder");
 
-                let timestamp = self.compute_met_timestamp(cut_block_absolute_time, abs_time)?;
-                let block = SimpleBlock::new_uncheked(&frame, 1, timestamp, false, None, false, false);
-                perf_trace!(block_timestamp, "Writing block to output");
-                self.write_block(block)?;
+                if force_keyframe {
+                    // Start a new cluster for the forced keyframe so the stream remains seekable.
+                    let cluster_rel = abs_time - cut_block_absolute_time;
+                    self.maybe_report_realtime_ratio(abs_time, cluster_rel);
+                    self.start_new_cluster(cluster_rel)?;
+                    self.cut_block_state = CutBlockState::Met {
+                        cut_block_absolute_time,
+                        last_cluster_relative_time: cluster_rel,
+                    };
+                    let block = SimpleBlock::new_uncheked(&frame, 1, 0, false, None, false, true);
+                    perf_trace!(block_timestamp, "Writing forced keyframe block to output");
+                    self.write_block(block)?;
+                    self.last_keyframe_abs_time = Some(abs_time);
+                } else {
+                    let timestamp = self.compute_met_timestamp(cut_block_absolute_time, abs_time)?;
+                    let block = SimpleBlock::new_uncheked(&frame, 1, timestamp, false, None, false, false);
+                    perf_trace!(block_timestamp, "Writing block to output");
+                    self.write_block(block)?;
+                }
                 self.last_encoded_abs_time = Some(abs_time);
             }
         }