Enable video gUM and try http://mozilla.github.io/webrtc-landing/gum_test.html few times. The camera HAL will be deadlock when preview stopping due to the preview buffer dones't return to camera HAL. I've created a hack according to following analysis from log. I'll discuss with :slee later. ---- 3049 02-05 08:30:50.864 I/PRLog ( 195): 40968[443c6700]: queueBuffer: E ==> camera could already get stop command at this point. 3050 02-05 08:30:50.864 I/PRLog ( 195): 40968[443c6700]: GonkNativeWindow::getCurrentBuffer 3051 02-05 08:30:50.864 I/PRLog ( 195): 40968[443c6700]: android::CameraGraphicBuffer::CameraGraphicBuffer(android::GonkNativeWindow*, uint32_t, uint32_t, mozilla::layers::SurfaceDescriptor):316 : this=45a4f8d0 3052 02-05 08:30:50.864 I/PRLog ( 195): 40968[443c6700]: bool mozilla::DOMCameraPreview::ReceiveFrame(void*, mozilla::ImageFormat, void (*)(mozilla::layers::Image*, void*, uint32_t, uint32_t)):186 : this=448f0420 3053 02-05 08:30:50.864 I/PRLog ( 195): 40968[443c6700]: queueBuffer: X 3054 02-05 08:30:50.864 V/EmulatedCamera_Device( 40): Select: Select, fd -1 3055 02-05 08:30:50.905 I/PRLog ( 195): 41200[43de4980]: dequeueBuffer: E 3056 02-05 08:30:50.905 I/PRLog ( 195): 41200[43de4980]: dequeueBuffer: Try again ==> fail to dequeue because camera received stop command 3057 02-05 08:30:50.944 I/Gecko ( 195): [Child 195] WARNING: nsWindow::GetNativeData not implemented for this type: file /home/alfredo/mozilla/mozilla-central/widget/xpwidgets/PuppetWidget.cpp, line 714 3058 02-05 08:30:50.954 I/Gecko ( 195): [Child 195] WARNING: We don't support transparent content with displayports, force it to be opqaue: file /home/alfredo/mozilla/mozilla-central/layout/base/nsDisplayList.cpp, line 1214 3059 02-05 08:30:51.064 I/PRLog ( 195): 1074414728[40222080]: Listener removed on purpose, mFinished = 1 3060 02-05 08:30:51.064 I/PRLog ( 195): 1074414728[40222080]: Sent recording-window-ended for window 4 (outer 1) 3061 02-05 08:30:51.064 I/PRLog ( 195): 1074414728[40222080]: mozilla::StopPreviewTask::StopPreviewTask(mozilla::CameraControlImpl*):573 : this=45af8fd0 3062 02-05 08:30:51.064 I/PRLog ( 195): 63968[4430ee00]: virtual nsresult mozilla::StopPreviewTask::Run():583 3063 02-05 08:30:51.064 I/PRLog ( 195): 63968[4430ee00]: nsresult mozilla::nsGonkCameraControl::StopPreviewInternal(bool): stopping preview (mDOMPreview=448f0420) 3064 02-05 08:30:51.064 I/PRLog ( 195): 63968[4430ee00]: void android::GonkCameraHardware::StopPreview():322 : this=44d72ac0 3065 02-05 08:30:51.064 V/EmulatedCamera_CallbackNotifier( 40): disableMessage: msg_type = 0x10 3066 02-05 08:30:51.064 V/EmulatedCamera_CallbackNotifier( 40): CAMERA_MSG_PREVIEW_FRAME 3067 02-05 08:30:51.064 V/EmulatedCamera_CallbackNotifier( 40): **** Currently enabled messages: 3068 02-05 08:30:51.064 V/EmulatedCamera_CallbackNotifier( 40): CAMERA_MSG_ERROR 3069 02-05 08:30:51.064 V/EmulatedCamera_CallbackNotifier( 40): CAMERA_MSG_FOCUS 3070 02-05 08:30:51.064 V/EmulatedCamera_CallbackNotifier( 40): CAMERA_MSG_ZOOM 3071 02-05 08:30:51.064 V/EmulatedCamera_CallbackNotifier( 40): CAMERA_MSG_PREVIEW_METADATA 3072 02-05 08:30:51.064 V/EmulatedCamera_Camera( 40): doStopPreview 3073 02-05 08:30:51.064 V/EmulatedCamera_Device( 40): stopDeliveringFrames 3074 02-05 08:30:51.064 V/EmulatedCamera_Device( 40): stopWorkerThread 3075 02-05 08:30:51.064 V/EmulatedCamera_Device( 40): Stopping emulated camera device's worker thread... 3076 02-05 08:30:51.064 V/EmulatedCamera_Device( 40): Requesting to stop worker thread!!! ==> camera HAL waits for buffer returning, but it won't happen.

With help from :slee, here is the patch.