Modify the Flow

Our Goal

In the previous section, we deployed a flow that takes input from a webcam. Now let's say we want to modify the flow to take input from a video file instead and make sure that our flow can stop itself when the video file has no more frames to read. To achieve this, we will need to:

1. Replace the Webcam Input node with a Server Media Input node and configure it to read from a video file
2. Update the input reference in the Webcam General Detection node to use the output from the Server Media Input node
3. Redeploy the flow and see the changes in action!

Select the Node

To add a new Server Media Input node:

• Click the button in the top-left corner to open the node selector
• Click on I/O to expand the category
• Drag and drop the Server Media Input node onto the canvas

Rewire the Flow

Let's replace the Webcam Input node with the new Server Media Input node we just added. To do that we:

• Select the Webcam Input node by clicking it
• Delete the node by clicking the Delete key on your keyboard (or press and hold the button on the node)
• Move the Server Media Input node to the position where the Webcam Input node was
• Connect the Time Interval Trigger node to the Server Media Input node by dragging from the output handle of the Time Interval Trigger node to the input handle of the Server Media Input node
• Connect the Server Media Input node to the General Detection node
• Connect the Server Media Input node (Error port) to the Stop node

Configure the Nodes

Specify the Video File Path

Now we need to configure the Server Media Input node to read from a video file. To do that:

• Click on the button on the Server Media Input node
• Under the Path to Media field, click on the button to browse the video file you want to use as input
  • Double-click the folder to open it, once you find the video file, select it (this highlights the file)
  • Click Select in the bottom-right corner of the file browser dialog
• Click Apply to save the changes
• Close the configuration dialog by clicking close (the x button in the top-right corner of the dialog or anywhere outside the dialog)

Update the Input Reference

Because we have replaced the Webcam Input node with a Server Media Input node, we also need to update the input reference in the Webcam General Detection node to use the output from the Server Media Input node instead. To do that:

• Click on the button on the Webcam General Detection node to open the configuration dialog
• You will see a warning under the Input Image field indicating that the input reference is broken.
• Click on it, navigate to the Server Media Input node
• Select frameOut output from the Server Media Input node as the new input reference
• Click Apply to save the changes

Auto Stopping Logic

As you might have noticed, we have connected the Error port of the Server Media Input node to the Stop node. This is because when the Server Media Input node reaches the end of the video file, it will output an error indicating that there are no more frames to read, and by connecting it to the Stop node, we can make sure that our deployment can stop itself when the video file has no more frames to read.

Save the Project

It's always a good practice to save your project after making changes. To save the project:

• Click on the button in the top-left corner of the app to open the main menu, or use Ctrl + S (or Cmd + S on Mac).
• Click on Save Project As..., or use Ctrl + Shift + S (or Cmd + Shift + S on Mac) to save the project with a new name
• Navigate to the folder where you want to save the project, enter a new name for the project, and click Save.

Save as is a good way to keep the original project intact and have a new project with the modifications you just made.

Redeploy the Flow

Awesome! Now we have successfully modified the flow to take input from a video file, with the logic to stop the flow when the video file has no more frames to read, and saved the modified flow as a new project.

Now let's deploy the flow again by clicking on the Deploy () button.

Navigate to the Dashboard page, and you should see the Image Frame widget showing the detected objects from the video file in real-time. Once the flow reaches the end of the video file, it will automatically stop and you will see that the status indicator in the bottom-left corner of the app changes from green (running) to grey (not deployed).

Shutdown Nara

To safely shutdown Nara:

• Make sure to stop any running flows by clicking the Stop () button in the Flows page.
• Navigate to the options page by clicking on the Options icon on the navigation bar.
• In the top-right corner of the General options page, click on Shutdown Nara button to shut down the app.
• Once Nara is shutdown, it will navigate to the login page. Note that you will not be able to access the app at all after it is shutdown until you start Nara again.

What's Next?

If you want to continue exploring and learning more about Nara, you can check out the Basic Course which will give you a comprehensive introduction to Nara's features and how to use them effectively.