# Device Queue Event This example shows how to use getQueueEvent function in order to be notified when one of the packets from selected streams arrive ## Demo ## Setup Please run the [install script](https://github.com/luxonis/depthai-python/blob/main/examples/install_requirements.py) to download all required dependencies. Please note that this script must be ran from git context, so you have to download the [depthai-python](https://github.com/luxonis/depthai-python) repository first and then run the script ```bash git clone https://github.com/luxonis/depthai-python.git cd depthai-python/examples python3 install_requirements.py ``` For additional information, please follow the [installation guide](https://docs.luxonis.com/software/depthai/manual-install.md). ## Source code #### Python ```python #!/usr/bin/env python3 """ This example demonstrates use of queue events to block a thread until a message arrives to any (of the specified) queue """ import cv2 import depthai as dai # Create pipeline pipeline = dai.Pipeline() # Define sources and outputs camRgb = pipeline.create(dai.node.ColorCamera) camMono = pipeline.create(dai.node.MonoCamera) xoutRgb = pipeline.create(dai.node.XLinkOut) xoutMono = pipeline.create(dai.node.XLinkOut) xoutRgb.setStreamName("rgb") xoutMono.setStreamName("mono") # Properties camRgb.setInterleaved(True) camRgb.setPreviewSize(300, 300) # Linking camRgb.preview.link(xoutRgb.input) camMono.out.link(xoutMono.input) # Connect to device and start pipeline with dai.Device(pipeline) as device: # Clear queue events device.getQueueEvents() while True: # Block until a message arrives to any of the specified queues queueName = device.getQueueEvent(("rgb", "mono")) # Getting that message from queue with name specified by the event # Note: number of events doesn't necessarily match number of messages in queues # because queues can be set to non-blocking (overwriting) behavior message = device.getOutputQueue(queueName).get() # Display arrived frames if type(message) == dai.ImgFrame: cv2.imshow(queueName, message.getCvFrame()) if cv2.waitKey(1) == ord('q'): break ``` #### C++ ```cpp #include // Includes common necessary includes for development using depthai library #include "depthai/depthai.hpp" int main() { // Create pipeline dai::Pipeline pipeline; // Define sources and outputs auto camRgb = pipeline.create(); auto camMono = pipeline.create(); auto xoutRgb = pipeline.create(); auto xoutMono = pipeline.create(); xoutRgb->setStreamName("rgb"); xoutMono->setStreamName("mono"); // Properties camRgb->setInterleaved(true); camRgb->setPreviewSize(300, 300); // Linking camRgb->preview.link(xoutRgb->input); camMono->out.link(xoutMono->input); // Connect to device and start pipeline dai::Device device(pipeline); // Clear queue events device.getQueueEvents(); while(true) { auto ev = device.getQueueEvent(); if(ev == "rgb") { auto rgb = device.getOutputQueue(ev)->get(); cv::imshow("rgb", rgb->getFrame()); } else if(ev == "mono") { auto mono = device.getOutputQueue(ev)->get(); cv::imshow("mono", mono->getFrame()); } int key = cv::waitKey(1); if(key == 'q' || key == 'Q') { return 0; } } return 0; } ``` ## Pipeline ### examples/device_queue_event.pipeline.json ```json { "pipeline": { "connections": [ { "node1Id": 0, "node1Output": "preview", "node1OutputGroup": "", "node2Id": 2, "node2Input": "in", "node2InputGroup": "" }, { "node1Id": 1, "node1Output": "out", "node1OutputGroup": "", "node2Id": 3, "node2Input": "in", "node2InputGroup": "" } ], "globalProperties": { "calibData": null, "cameraTuningBlobSize": null, "cameraTuningBlobUri": "", "leonCssFrequencyHz": 700000000.0, "leonMssFrequencyHz": 700000000.0, "pipelineName": null, "pipelineVersion": null, "sippBufferSize": 18432, "sippDmaBufferSize": 16384, "xlinkChunkSize": -1 }, "nodes": [ [ 0, { "id": 0, "ioInfo": [ [ [ "", "inputConfig" ], { "blocking": false, "group": "", "id": 1, "name": "inputConfig", "queueSize": 8, "type": 3, "waitForMessage": false } ], [ [ "", "raw" ], { "blocking": false, "group": "", "id": 6, "name": "raw", "queueSize": 8, "type": 0, "waitForMessage": false } ], [ [ "", "still" ], { "blocking": false, "group": "", "id": 7, "name": "still", "queueSize": 8, "type": 0, "waitForMessage": false } ], [ [ "", "inputControl" ], { "blocking": true, "group": "", "id": 2, "name": "inputControl", "queueSize": 8, "type": 3, "waitForMessage": false } ], [ [ "", "video" ], { "blocking": false, "group": "", "id": 3, "name": "video", "queueSize": 8, "type": 0, "waitForMessage": false } ], [ [ "", "isp" ], { "blocking": false, "group": "", "id": 4, "name": "isp", "queueSize": 8, "type": 0, "waitForMessage": false } ], [ [ "", "preview" ], { "blocking": false, "group": "", "id": 5, "name": "preview", "queueSize": 8, "type": 0, "waitForMessage": false } ], [ [ "", "frameEvent" ], { "blocking": false, "group": "", "id": 8, "name": "frameEvent", "queueSize": 8, "type": 0, "waitForMessage": false } ] ], "name": "ColorCamera", "properties": { "boardSocket": -1, "cameraName": "", "colorOrder": 0, "fp16": false, "fps": 30.0, "imageOrientation": -1, "initialControl": { "aeLockMode": false, "aeMaxExposureTimeUs": 0, "aeRegion": { "height": 0, "priority": 0, "width": 0, "x": 0, "y": 0 }, "afRegion": { "height": 0, "priority": 0, "width": 0, "x": 0, "y": 0 }, "antiBandingMode": 0, "autoFocusMode": 3, "awbLockMode": false, "awbMode": 0, "brightness": 0, "captureIntent": 0, "chromaDenoise": 0, "cmdMask": 0, "contrast": 0, "controlMode": 0, "effectMode": 0, "expCompensation": 0, "expManual": { "exposureTimeUs": 0, "frameDurationUs": 0, "sensitivityIso": 0 }, "frameSyncMode": 0, "lensPosAutoInfinity": 0, "lensPosAutoMacro": 0, "lensPosition": 0, "lensPositionRaw": 0.0, "lowPowerNumFramesBurst": 0, "lowPowerNumFramesDiscard": 0, "lumaDenoise": 0, "saturation": 0, "sceneMode": 0, "sharpness": 0, "strobeConfig": { "activeLevel": 0, "enable": 0, "gpioNumber": 0 }, "strobeTimings": { "durationUs": 0, "exposureBeginOffsetUs": 0, "exposureEndOffsetUs": 0 }, "wbColorTemp": 0 }, "interleaved": true, "isp3aFps": 0, "ispScale": { "horizDenominator": 0, "horizNumerator": 0, "vertDenominator": 0, "vertNumerator": 0 }, "numFramesPoolIsp": 3, "numFramesPoolPreview": 4, "numFramesPoolRaw": 3, "numFramesPoolStill": 4, "numFramesPoolVideo": 4, "previewHeight": 300, "previewKeepAspectRatio": true, "previewWidth": 300, "rawPacked": null, "resolution": 0, "sensorCropX": -1.0, "sensorCropY": -1.0, "stillHeight": -1, "stillWidth": -1, "videoHeight": -1, "videoWidth": -1 } } ], [ 1, { "id": 1, "ioInfo": [ [ [ "", "inputControl" ], { "blocking": true, "group": "", "id": 9, "name": "inputControl", "queueSize": 8, "type": 3, "waitForMessage": false } ], [ [ "", "out" ], { "blocking": false, "group": "", "id": 10, "name": "out", "queueSize": 8, "type": 0, "waitForMessage": false } ], [ [ "", "raw" ], { "blocking": false, "group": "", "id": 11, "name": "raw", "queueSize": 8, "type": 0, "waitForMessage": false } ], [ [ "", "frameEvent" ], { "blocking": false, "group": "", "id": 12, "name": "frameEvent", "queueSize": 8, "type": 0, "waitForMessage": false } ] ], "name": "MonoCamera", "properties": { "boardSocket": -1, "cameraName": "", "fps": 30.0, "imageOrientation": -1, "initialControl": { "aeLockMode": false, "aeMaxExposureTimeUs": 0, "aeRegion": { "height": 0, "priority": 0, "width": 0, "x": 0, "y": 0 }, "afRegion": { "height": 0, "priority": 0, "width": 0, "x": 0, "y": 0 }, "antiBandingMode": 0, "autoFocusMode": 3, "awbLockMode": false, "awbMode": 0, "brightness": 0, "captureIntent": 0, "chromaDenoise": 0, "cmdMask": 0, "contrast": 0, "controlMode": 0, "effectMode": 0, "expCompensation": 0, "expManual": { "exposureTimeUs": 0, "frameDurationUs": 0, "sensitivityIso": 0 }, "frameSyncMode": 0, "lensPosAutoInfinity": 0, "lensPosAutoMacro": 0, "lensPosition": 0, "lensPositionRaw": 0.0, "lowPowerNumFramesBurst": 0, "lowPowerNumFramesDiscard": 0, "lumaDenoise": 0, "saturation": 0, "sceneMode": 0, "sharpness": 0, "strobeConfig": { "activeLevel": 0, "enable": 0, "gpioNumber": 0 }, "strobeTimings": { "durationUs": 0, "exposureBeginOffsetUs": 0, "exposureEndOffsetUs": 0 }, "wbColorTemp": 0 }, "isp3aFps": 0, "numFramesPool": 3, "numFramesPoolRaw": 3, "rawPacked": null, "resolution": 0 } } ], [ 2, { "id": 2, "ioInfo": [ [ [ "", "in" ], { "blocking": true, "group": "", "id": 13, "name": "in", "queueSize": 8, "type": 3, "waitForMessage": true } ] ], "name": "XLinkOut", "properties": { "maxFpsLimit": -1.0, "metadataOnly": false, "streamName": "rgb" } } ], [ 3, { "id": 3, "ioInfo": [ [ [ "", "in" ], { "blocking": true, "group": "", "id": 14, "name": "in", "queueSize": 8, "type": 3, "waitForMessage": true } ] ], "name": "XLinkOut", "properties": { "maxFpsLimit": -1.0, "metadataOnly": false, "streamName": "mono" } } ] ] } } ``` ### Need assistance? Head over to [Discussion Forum](https://discuss.luxonis.com/) for technical support or any other questions you might have.