5. Configuring applications

The demo config file uses YAML format to define input sources, models, outputs and finally the flows which defines how everything is connected. Config files for out-of-box demos are kept in edgeai-gst-apps/configs folder. The folder contains config files for all the use cases and also multi-input and multi-inference case. The folder also has a template YAML file app_config_template.yaml which has detailed explanation of all the parameters supported in the config file.

Config file is divided in 4 sections:

  1. Inputs

  2. Models

  3. Outputs

  4. Flows

5.1. Inputs

The input section defines a list of supported inputs like camera, video files etc. Their properties like shown below.

    input0:                                                         #Camera Input
        source: /dev/video-usb-cam0                                 #Device file entry of the camera
        format: jpeg                                                #Input data format supported by camera
        width: 1280                                                 #Width and Height of the input
        height: 720
        framerate: 30                                               #Framerate of the source

    input1:                                                         #Video Input
        source: /opt/edgeai-test-data/videos/video0_1280_768.h264   #Video file
        format: h264                                                #File encoding format
        width: 1280
        height: 768
        framerate: 30

    input2:                                                         #Image Input
        source: /opt/edgeai-test-data/videos/images/%04d.jpg        #Sequence of Image files, printf style formatting is used
        width: 1280
        height: 720
        index: 0                                                    #Starting Index (optional)
        framerate: 1

All supported inputs are listed in template config file. Below are the details of most commonly used inputs.

5.1.1. Camera sources (v4l2)

v4l2src GStreamer element is used to capture frames from camera sources which are exposed as v4l2 devices. In Linux, there are many devices which are implemented as v4l2 devices. Not all of them will be camera devices. You need to make sure the correct device is configured for running the demo successfully.

init_script.sh is ran as part of systemd, which detects all cameras connected and prints the detail like below in the console:

/opt/edgeai-gst-apps# ./init_script.sh
USB Camera detected
    device = /dev/video-usb-cam0
    format = jpeg
CSI Camera 0 detected
    device = /dev/video-rpi-cam0
    format = [fmt:SRGGB8_1X8/1920x1080]
    subdev_id = /dev/v4l-rpi-subdev0
    isp_required = yes

script can also be run manually later to get the camera details.

From the above log we can determine that 1 USB camera is connected (/dev/video-usb-cam0), and 1 CSI camera is connected (/dev/video-rpi-cam0) which is IMX219 raw sensor and needs ISP.

Using this method, you can configure correct device for camera capture in the input section of config file.

    source: /dev/video-usb-cam0     #USB Camera
    format: jpeg                    #if connected USB camera supports jpeg
    width: 1280
    height: 720
    framerate: 30

    source: /dev/video-rpi-cam0     #IMX219 raw sensor that needs ISP
    format: rggb                    #ISP will be added in the pipeline
    width: 1920
    height: 1080
    framerate: 30
    subdev-id: /dev/v4l-rpi-subdev0 #needed by ISP to control sensor params via ioctls

Make sure to configure correct format for camera input. jpeg for USB camera that supports MJPEG (Ex. C270 logitech USB camera). auto for CSI camera to allow GStreamer to negotiate the format. rggb for sensor that needs ISP.

5.1.2. Video sources

H.264 and H.265 encoded videos can be provided as input sources to the demos. Sample video files are provided under /opt/edgeai-test-data/videos/

    source: /opt/edgeai-test-data/videos/video0_1280_768.h264
    format: h264
    width: 1280
    height: 768
    framerate: 30

    source: /opt/edgeai-test-data/videos/video0_1920_1088.h264
    format: h264
    width: 1920
    height: 1088
    framerate: 30

Make sure to configure correct format for video input as shown above. By default the format is set to auto which will then use the GStreamer bin decodebin instead.

5.1.3. Image sources

JPEG compressed images can be provided as inputs to the demos. A sample set of images are provided under /opt/edgeai-test-data/images. The names of the files are numbered sequentially and incrementally and the demo plays the files at the fps specified by the user.

    source: /opt/edgeai-test-data/images/%04d.jpg
    width: 1280
    height: 720
    index: 0
    framerate: 1

5.1.4. RTSP sources

H.264 encoded video streams either coming from a RTSP compliant IP camera or via RTSP server running on a remote PC can be provided as inputs to the demo.

    source: rtsp:// # rtsp stream url, replace this with correct url
    width: 1280
    height: 720
    framerate: 30


Usually video streams from any IP camera will be encrypted and cannot be played back directly without a decryption key. We tested RTSP source by setting up an RTSP server on a Ubuntu 18.04 PC by referring to this writeup, Setting up RTSP server on PC

5.2. Models

The model section defines a list of models that are used in the demo. Path to the model directory is a required argument for each model and rest are optional properties specific to given use cases like shown below.

        model_path: /opt/model_zoo/TFL-OD-2020-ssdLite-mobDet-DSP-coco-320x320      #Model Directory
        viz_threshold: 0.6                                                          #Visualization threshold for adding bounding boxes (optional)
        model_path: /opt/model_zoo/ONR-CL-6360-regNetx-200mf
        topN: 5                                                                     #Number of top N classes (optional)
        model_path: /opt/model_zoo/ONR-SS-8610-deeplabv3lite-mobv2-ade20k32-512x512
        alpha: 0.4                                                                  #alpha for blending segmentation mask (optional)

Below are some of the use case specific properties:

  1. viz_threshold: Score threshold to draw the bounding boxes for detected objects in object detection. This can be used to control the number of boxes in the output, increase if there are too many and decrease if there are very few

  2. topN: Number of most probable classes to overlay on image classification output

  3. alpha: This determines the weight of the mask for blending the semantic segmentation output with the input image alpha * mask + (1 - alpha) * image

The content of the model directory and its structure is discussed in detail in Import Custom Models

5.3. Outputs

The output section defines a list of supported outputs.

    output0:                                                         #Display Output
        sink: kmssink
        width: 1920                                                  #Width and Height of the output
        height: 1080
        overlay-perf-type: graph                                     #Overlay performance stat (graph or text default:No overlay)
        connector: 39                                                #Connector ID for kmssink (optional)

    output1:                                                         #Video Output
        sink: /opt/edgeai-test-data/outputs/output_video.mkv         #Output video file
        width: 1920
        height: 1080

    output2:                                                         #Image Output
        sink: /opt/edgeai-test-data/outputs/output_image_%04d.jpg    #Image file name, printf style formatting is used
        width: 1920
        height: 1080

        sink: remote                                                 #Publish output to udp port as jpeg encoded frames
        width: 1920
        height: 1080
        port: 8081                                                   #udp port (default:8081)
        host:                                              #udp host (default:
        encoding: jpeg                                               #encoding type (jpeg or mp4)

All supported outputs are listed in template config file. Below are the details of most commonly used outputs

5.3.1. Display sink (kmssink)

When you have only one display connected to the SK, kmssink will try to use it for displaying the output buffers. In case you have connected multiple display monitors (e.g. Display Port and HDMI), you can select a specific display for kmssink by passing a specific connector ID number. Following command finds out the connected displays available to use.

Note: Run this command to check which display is connected. The first number in each line is the connector-id to be used in the next step.

/opt/edgeai-gst-apps# modetest -M tidss -c | grep connected
39      38      connected       DP-1            530x300         12      38
48      0       disconnected    HDMI-A-1        0x0             0       47

Configure the required connector ID in the output section of the config file.

5.3.2. Video sinks

The post-processed outputs can be encoded in H.264 format and stored on disk. Please specify the location of the video file in the configuration file.

    sink: /opt/edgeai-test-data/outputs/output_video.mkv    #(.mkv or .mp4 or .mov)
    width: 1920
    height: 1080

5.3.3. Image sinks

The post-processed outputs can be stored as JPEG compressed images. Please specify the location of the image files in the configuration file. The images will be named sequentially and incrementally as shown.

    sink: /opt/edgeai-test-data/outputs/output_image_%04d.jpg
    width: 1920
    height: 1080

5.3.4. Remote sinks

Post-processed frames can be encoded as jpeg or h264 frames and send as udp packets to a port. Please specify the sink as remote in the configuration file. The udp port and host to send packets to can be defined. If not, default port is 8081 and host is

    sink: remote
    width: 1920
    height: 1080
    port: 8081
    encoding: jpeg  #(jpeg or h264)

A NodeJS server is provided under /opt/edgeai-gst-apps/scripts/remote_streaming which establishes a node server on the target and listens to the udp port (8081) on localhost ( and can be used to view the frames remotely.

/opt/edgeai-gst-apps# node scripts/remote_streaming/server.js

5.4. Flows

The flows section defines how inputs, models and outputs are connected. Multiple flows can be defined to achieve multi input, multi inference as shown


The format of specifying flows is changed as of 08.05.00 release to enable multiple outputs in the same sub-flow The older config files may not be compatible from this release onwards and should be changed to below format

    # flowname : [input,mode1,output,[mosaic_pos_x,mosaic_pos_y,width,height]]
    flow0: [input0,model0,output0,[160,90,800,450]]
    flow1: [input0,model1,output0,[960,90,800,450]]
    flow2: [input1,model2,output0,[160,540,800,450]]
    flow3: [input1,model3,output0,[960,540,800,450]]

Each flow defined here has exactly 1 input and 1 model. If multiple flows have same input, they are clubbed together internally in the application for optimization. Along with input, models and outputs it is required to define n mosaics which are the position of the inference output in the final output plane. This is needed because multiple inference outputs can be rendered to same output (Ex: Display).

5.5. GStreamer plugins

The edgeai-gst-apps essentially constructs GStreamer pipelines for dataflow. This pipeline is constructed optimally and dynamically based on a pool of specific plugins available on the platform. The defined pool of plugins for different platform can be found in edgeai-gst-apps/configs/gst_plugin_maps.yaml file.

This file contains the plugin used for certain task and the property of plugin (if applicable).

5.5.1. Default GStreamer plugins map for AM62Ax

        element: tiovxdlcolorconvert
            out-pool-size: 4
        element: tiovxcolorconvert
            target: [0,1]
            out-pool-size: 4
        element: tiovxmultiscaler
            target: [0,1]       #[MSC targets to balance loads across]
        element: tiovxdlpreproc
            out-pool-size: 4
        element: tiovxmosaic
        element: tiovxisp
        element: tiovxldc
        element: v4l2h264dec
            capture-io-mode: 5  #[setting the mode for decoder]
        element: v4l2h265dec
        element: v4l2h264enc
    h265enc: null
        element: jpegenc
        target: dsp             #[dsp for c7x offload, arm for no offload]
        core-id: [1]            #[specify list of c7x cores to offload models]