feat(video-streamer): add codec-aware VP9 keyframe detection for session shadowing by irvingoujAtDevolution · Pull Request #1705 · Devolutions/devolutions-gateway

irvingouj@Devolutions (irvingoujAtDevolution) · 2026-03-10T17:07:50Z

Summary

Add codec-aware VP9 keyframe detection in tag_writers.rs so the streamer correctly identifies keyframes for both VP8 and VP9 codecs during session shadowing
Improve unified shutdown correctness with AbortOnDrop bridge guard and shutdown-reason-aware final messages (Error vs End)
Add warning log when when_eof oneshot sender is dropped unexpectedly

Test plan

Verify VP9 session shadowing correctly detects keyframes and starts playback from the latest keyframe
Verify VP8 session shadowing still works as before (regression check)
Verify shutdown paths: external shutdown, client disconnect, and error conditions all send the correct final message
Verify no hanging tasks on stream exit (AbortOnDrop ensures bridge task cleanup)

🤖 Generated with Claude Code

…ion shadowing The existing keyframe detection only handled VP8 frames. This adds proper VP9 keyframe detection based on the VP9 bitstream specification, supporting all profiles (0-3). The codec type is now threaded through the iterator and block tag layers so keyframe checks use the correct codec-specific logic. Also sets VpxEncoderPreset::BestPerformance for improved re-encoding throughput. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Send Error (not End) to client when shutdown is caused by a stream error - Use AbortOnDrop guard for bridge task to handle early returns/bails - Remove dead UserFriendlyError::UnexpectedEOF variant Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

github-actions · 2026-03-10T17:08:09Z

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Copilot

Pull request overview

Adds periodic, interval-based keyframe forcing during re-encoding so the outgoing WebM stream remains seekable over time (and starts new clusters on forced keyframes), and improves EOF-wait robustness by warning when the when_eof oneshot sender is dropped.

Changes:

Track last forced keyframe time and force a new keyframe every KEYFRAME_INTERVAL_MS, starting a new cluster for that keyframe.
Log a warning and treat EOF-wait as shutdown if the when_eof oneshot sender is unexpectedly dropped.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
crates/video-streamer/src/streamer/tag_writers.rs	Adds interval-based forced keyframes and cluster splitting to improve seekability/resilience.
crates/video-streamer/src/streamer/mod.rs	Adds a warning log when the `when_eof` oneshot sender is dropped unexpectedly.

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Copilot · 2026-03-11T05:22:25Z

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

+/// 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;
+


This PR description mentions adding “codec-aware VP9 keyframe detection in tag_writers.rs”, but the change here introduces periodic forced keyframes (interval-based) rather than keyframe detection. If VP9 detection work is happening elsewhere, consider updating the PR description; otherwise, ensure the intended VP9 keyframe-detection fix is included.

Copilot · 2026-03-11T05:22:25Z

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

@@ -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 {


The new periodic keyframe forcing / cluster-splitting behavior doesn’t appear to be covered by tests. Since this is important for session shadowing correctness, consider adding an integration test (similar to existing webm_stream_* tests) that runs long enough to cross KEYFRAME_INTERVAL_MS and asserts that a new cluster starts and the corresponding SimpleBlock is marked as a keyframe.

Copilot · 2026-03-11T05:22:25Z

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

+                    self.start_new_cluster(cluster_rel)?;
+                    self.cut_block_state = CutBlockState::Met {
+                        cut_block_absolute_time,
+                        last_cluster_relative_time: cluster_rel,
+                    };


In the forced-keyframe path, cut_block_state is updated to Met { .. last_cluster_relative_time: cluster_rel } before start_new_cluster(cluster_rel)? runs. If start_new_cluster fails (e.g., write error), the writer state is mutated even though the new cluster wasn't actually emitted. Consider calling start_new_cluster first and only updating cut_block_state after it succeeds (mirrors the ordering used in compute_met_timestamp).

irvingouj@Devolutions (irvingoujAtDevolution) and others added 4 commits March 10, 2026 12:24

done

f0101ef

fix(video-streamer): log when_eof oneshot sender dropped unexpectedly

29e62f5

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Benoît Cortier (CBenoit) requested a review from Copilot March 11, 2026 05:16

Copilot started reviewing on behalf of Benoît Cortier (CBenoit) March 11, 2026 05:17 View session

Copilot AI reviewed Mar 11, 2026

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feat(video-streamer): add codec-aware VP9 keyframe detection for session shadowing#1705

feat(video-streamer): add codec-aware VP9 keyframe detection for session shadowing#1705
irvingouj@Devolutions (irvingoujAtDevolution) wants to merge 4 commits intomasterfrom
fix/add-keyframe-every-10s

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irvingouj@Devolutions (irvingoujAtDevolution) commented Mar 10, 2026

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