Solving the MJPEG Video Stream Update Issue in SwiftUI

Discover how to fix the issue of image updates in your SwiftUI application when streaming `MJPEG` video by ensuring proper use of `ObservableObject`.
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This video is based on the question https://stackoverflow.com/q/69640090/ asked by the user 'gotnull' ( https://stackoverflow.com/u/264802/ ) and on the answer https://stackoverflow.com/a/69640882/ provided by the user 'Scott Thompson' ( https://stackoverflow.com/u/415303/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting MJPEG Video Stream Updates in SwiftUI

When developing applications using SwiftUI, streaming video can be a formidable challenge, particularly when ensuring that the video feed updates correctly in the user interface. A common issue that developers encounter is that the images within the viewer do not refresh as frames are received from the stream. This guide addresses this problem, specifically pertaining to the use of the MJPEG video stream and how to achieve real-time updates within your SwiftUI views.

Understanding the Problem

In our current implementation, the streaming video is set up with a class MJPEGStream, which utilizes an observable object for SwiftUI to watch for changes in the data. However, the issue arises because even though the video stream is functioning correctly (confirmed via a web browser) and the frames are received successfully, the Image in MpegView does not get updated. This occurs because of how the observable properties are set up in the MJPEGStream and MJPEGStreamLib classes.

Key Observations:

The property stream in MJPEGStream points to an instance of MJPEGStreamLib.

The only time this property changes is upon the initial creation of MpegView, which means even if the underlying object is updated with new images, the pointer remains unchanged—thus, the view does not re-render.

Proposed Solution

To fix the issue of the image not updating in the view, we need to modify the structure of our observable objects and properties. Here are the steps to achieve this:

1. Refactor MJPEGStreamLib to be Observable

We want to allow the MJPEGStreamLib class to notify SwiftUI of changes. This can be achieved by making it conform to the ObservableObject protocol and marking the image property as @ Published. Here’s how to do it:

Update MJPEGStreamLib Class

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2. Modify MJPEGStream Class

You can keep MJPEGStream as is, but you need to ensure when you access the image in MpegView, you reference the image from MJPEGStreamLib correctly.

3. Adjust Your SwiftUI View

In your MpegView, since mjpegStream is now referencing the observable and the image is published, you should be able to render the image properly when it updates.

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Summary

By changing the implementation of the MJPEGStreamLib to be an ObservableObject and marking the image property with @ Published, you enable the SwiftUI view system to properly respond to the changes in the image as frames are received from the stream. This ensures that every new image from the video feed is displayed accurately on the screen, giving users a seamless streaming experience.

This slight adjustment in your class architecture goes a long way to making your SwiftUI application not just functional but also responsive and user-friendly.

Now that you're equipped to handle MJPEG streaming updates in SwiftUI, enjoy building your application!

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