Exercise3.md

Exercise 3 - Add VNC client for GUI and changing the attribute of one of the writer app

Synopsis

In Exercise 3, we will enhance our MXL environment by integrating a VNC client with a lightweight Linux desktop container. This setup provides a graphical interface that allows you to visualize actual video outputs from MXL writer applications in real-time.

You'll learn how to modify attributes of an MXL writer application - specifically changing the overlay text on one of the video flows - and observe these changes immediately through the VNC viewer.

This exercise also showcases the gstreamer clip player plugin (added in PR #22), which enables media transport stream files to be written directly into an MXL domain. Together, these components provide a tangible demonstration of MXL's capabilities through interactive video writer and reader test applications.

   graph
      direction LR
         subgraph Node/Host
            subgraph docker_writer_1 [docker]
                  direction LR
                  gstreamer_writer_1[Gstreamer writer]
                  mxl_sdk_writer_1[MXL SDK]
                  gstreamer_writer_1 --> mxl_sdk_writer_1
            end
             
             subgraph docker_writer_2 [docker]
                  direction LR
                  gstreamer_writer_2[Gstreamer clip-player]
                  mxl_sdk_writer_2[MXL SDK]
                  gstreamer_writer_2 --> mxl_sdk_writer_2
            end

            subgraph docker_reader_1 [docker]
                  direction LR
                  gstreamer_reader_1[Gstreamer Reader]
                  mxl_sdk_reader_1[MXL SDK]
                  mxl_sdk_reader_1 --> gstreamer_reader_1
            end

            subgraph docker_reader_2 [docker]
               direction LR
               gstreamer_reader_2[WebRTC Player]
               mxl_sdk_reader_2[MXL SDK]
               mxl_sdk_reader_2 --> gstreamer_reader_2
            end

            tmpfs([tmpfs<br>/Volumes/mxl/domain_1])

            mxl_sdk_writer_1 --> tmpfs
            mxl_sdk_writer_2 --> tmpfs
            tmpfs --> mxl_sdk_reader_1
            tmpfs --> mxl_sdk_reader_2
         end

         %% Styling
         linkStyle default stroke:black,stroke-width:2px
         style docker_writer_1 fill:#cce6ff,color:black,stroke:#333,stroke-width:3px
         style docker_writer_2 fill:#cce6ff,color:black,stroke:#333,stroke-width:3px
         style docker_reader_1 fill:#cce6ff,color:black,stroke:#333,stroke-width:3px
         style docker_reader_2 fill:#cce6ff,color:black,stroke:#333,stroke-width:3px
         style gstreamer_writer_1 fill:#66b3ff,color:black,stroke:#333,stroke-width:2px
         style gstreamer_writer_2 fill:#66b3ff,color:black,stroke:#333,stroke-width:2px
         style gstreamer_reader_1 fill:#66b3ff,color:black,stroke:#333,stroke-width:2px
         style gstreamer_reader_2 fill:#66b3ff,color:black,stroke:#333,stroke-width:2px
         style mxl_sdk_writer_1 fill:#007bff,color:white,stroke:#333,stroke-width:2px
         style mxl_sdk_writer_2 fill:#007bff,color:white,stroke:#333,stroke-width:2px
         style mxl_sdk_reader_1 fill:#007bff,color:white,stroke:#333,stroke-width:2px
         style mxl_sdk_reader_2 fill:#007bff,color:white,stroke:#333,stroke-width:2px
         style tmpfs fill:#ffe0b3,color:black,stroke:#333,stroke-width:2px

Steps

1. Go to exercise 3 folder

   cd ~/mxl-hands-on/docker/exercise-3
   

2. Identify the mxl domain with a domain_def.json in to allow the webRTC player application to discover mxl flows in the domain.

   cp ./data/domain_def.json /Volumes/mxl/domain_1
   

3. Look at the docker-compose.yaml file and notice the addition of the mxl2webrtc and mediamtx containers. These containers are there to give you access to a web application that will convert mxl flow into webrtc and display them in your browser.

   cat docker-compose.yaml
   

4. Start the containers

   docker compose up -d # For linux based system
   

   ./start-mac.sh # For mac based system
   

5. Use the WebRTC player application to look at the newly created mxl flows. You can reach the webRTC player in your browser with the following information:

App	URL	API Swagger Page
MXL to WebRTC	http://localhost:9601	http://localhost:9601/docs

With what you learned so far, can you look at all mxl flows?

When you are done experimenting, do not forget to shutdown your containers.

docker compose down # For linux based system

./stop-mac.sh # For mac based system

Extra information for Exercise 3

Exercise 3 is transitioning from theoretical understanding and command-line inspection to direct visual confirmation of MXL's functionality. It also introduces the concept of dynamically influencing media flows, a key aspect of real-time broadcast and production environments.

Exploring mxl-gst-testsrc and mxl-gst-sink

• mxl-gst-testsrc (Writer): This is the GStreamer-based application used by your MXL writers to generate video and audio. In this exercise, you're interacting with the -t parameter.
  • The -t (text overlay) parameter allows you to add a customizable text string directly onto the video frames generated by the videotestsrc.
• mxl-gst-sink (Reader/Viewer): This application acts as an MXL reader and uses GStreamer to display the video.
  • It takes the -d (domain) and -v (video flow ID) or -a(audio flow ID) parameters to specify which MXL domain to connect to and which specific flow to consume.
  • It translates the MXL grains (V210 format in this case) into a displayable video stream.

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