Fixed the Android Robot video feed freezing issue in the Flutter Controller. by harishthakur52 · Pull Request #551 · ob-f/OpenBot

harishthakur52 · 2026-10-09T12:40:33Z

Tested for

Android robot -> Android controller
Android robot -> Ios controller
Android robot -> Web controller

Also tested switching simultaneously between different fragments with real robot.

thias15 · 2026-10-10T05:00:14Z

Thanks for the fix and device testing. Two concerns:

The web and native Android controllers recreate their WebRTC connection on STOP/START, but the robot now reuses its connection without sending a new offer. Could you check that video resumes after toggling controller mode off and on?
SWITCH_CAMERA is now rejected whenever a local preview is active. Could we route it to the preview camera so remote front/back switching still works on Free Roam and Logger?

Please cover both cases in testing.

harishthakur52 · 2026-10-12T07:19:12Z

The robot now sends a fresh offer on every START, and the Flutter controller accepts it. Tested: video comes back after toggling controller mode off and on.
Tested: front/back camera switching works in Free Roam and Logger.

thias15 · 2026-10-16T05:24:03Z

Thanks for addressing both concerns. One remaining edge case: the delayed camera-switch callback can run after closeCall() clears videoCapturer, causing a crash if the controller disconnects or controller mode is turned off during the 300 ms delay. Could you cancel pending switches during cleanup and guard against callbacks from a previous session?

Copilot

🟡 Changes recommended

Preview lifecycle gaps, a signaling race, and incomplete resource disposal leave freezing and reliability issues unresolved.

5 open issues

What changed in this PR

This PR addresses Android robot video freezes by sharing preview frames with WebRTC and refreshing controller connections when video restarts.

Changes:

Shares CameraX preview frames and manages camera handoffs.
Reworks call teardown, restart, and signaling handling.
Serializes Flutter signaling and replaces connections for new offers.

File	Description
controller/flutter/lib/screens/controller.dart	Queues signaling and replaces connections on new offers.
android/robot/src/main/java/org/openbot/app/robot/env/WebRtcServer.java	Adds shared-frame streaming and revises call lifecycle handling.
android/robot/src/main/java/org/openbot/app/robot/env/PhoneController.java	Restarts video when reusing an open connection.
android/robot/src/main/java/org/openbot/app/robot/common/CameraFragment.java	Registers preview ownership and forwards camera frames.

_{Review effort: Balanced}

+            if (peerConnection == null) {
+              // Late message after the call closed. Throwing here would end this subscription.
+              Log.d(TAG, "Ignoring WebRTC event: no active call");
+              return;


    try {
      if (cameraProvider != null) {
        cameraProvider.unbindAll();
+        WebRtcServer.setLocalPreviewActive(this, true, this::switchCameraForController);


  public void onDestroy() {
    super.onDestroy();
    cameraExecutor.shutdown();
+    WebRtcServer.setLocalPreviewActive(this, false, null);


+    mediaStream = null;
+    videoSender = null;
+    audioSender = null;
+    videoTrackFromCamera = null;
+    localAudioTrack = null;


+    // The robot starts a new call with a fresh offer every time it restarts video, so a second
+    // offer belongs to a new call: replace the peer connection instead of renegotiating on it.
+    if (await _peerConnection?.getRemoteDescription() != null) {
+      await _peerConnection?.close();


- Handle start/stop and controller signaling on the main thread so they can't race with closeCall(). - Always resume the local preview after an interrupted camera switch. - Release preview ownership if camera binding fails. - Dispose local stream/tracks and the replaced Flutter peer connection.

thias15 · 2026-10-18T06:26:28Z

Thanks for the fixes! I pushed a follow-up commit for the remaining review points:

Start/stop and signaling now run on the main thread, so they can't race with teardown.
The robot's preview always resumes after an interrupted camera switch.
If camera binding fails, WebRTC falls back to its own camera.
Fixed resource leaks on teardown, on both the robot and the Flutter controller.

Pausing the feed while the robot app is on a settings screen is expected, so I left that as is.

Could you re-test on a device before we merge?

Connect each controller (Android, iOS, web) and check video.
Toggle controller mode off/on a few times.
Switch camera from the controller in Free Roam and Logger.
Disconnect right after connecting, then reconnect.
Switch camera and immediately disconnect; the robot preview should come back.

harishthakur52 · 2026-10-19T07:57:36Z

Thanks for the fixes! I pushed a follow-up commit for the remaining review points:

Start/stop and signaling now run on the main thread, so they can't race with teardown.

The robot's preview always resumes after an interrupted camera switch.

If camera binding fails, WebRTC falls back to its own camera.

Fixed resource leaks on teardown, on both the robot and the Flutter controller.

Pausing the feed while the robot app is on a settings screen is expected, so I left that as is.

Could you re-test on a device before we merge?

Connect each controller (Android, iOS, web) and check video.

Toggle controller mode off/on a few times.

Switch camera from the controller in Free Roam and Logger.

Disconnect right after connecting, then reconnect.

Switch camera and immediately disconnect; the robot preview should come back.

Thanks for the follow-up! Re-tested on device with 403b845 on the Android, iOS and web controllers: all 5 scenarios pass. Video works, controller mode off/on resumes video, camera switch works in Free Roam and Logger, reconnecting works, and the preview comes back after a switch followed by an immediate disconnect.

Agreed on the settings screen pause.

…android/robot-connection

thias15

Tested on device by the author; review comments addressed.

Improve robot to Flutter controller video feed on Android devices

9afa7b2

Fix WebRTC restart and preview camera switch

50dd443

Fix camera switch callback crash on disconnect

5dd330f

thias15 requested a balanced review from Copilot October 18, 2026 05:02

Copilot started reviewing on behalf of thias15 October 18, 2026 05:03

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Copilot AI reviewed Oct 18, 2026

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harishthakur52 added 2 commits October 19, 2026 13:30

Restore mute toggle to mute audio only

78311db

Merge branch 'master' of https://github.com/3dwesupport/OpenBot into …

14d9571

…android/robot-connection

thias15 mentioned this pull request Oct 19, 2026

Remove legacy Android controller and Nearby transport #559

Merged

Format compile_all.py with black

5a6a767

thias15 approved these changes Oct 20, 2026

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thias15 merged commit 379989d into ob-f:master Oct 20, 2026
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Fixed the Android Robot video feed freezing issue in the Flutter Controller. - #551

Fixed the Android Robot video feed freezing issue in the Flutter Controller.#551
thias15 merged 7 commits into
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3dwesupport:android/robot-connection

harishthakur52 commented Oct 9, 2026

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harishthakur52 commented Oct 9, 2026

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