Paella 7 can fail is there is no default Image set

[mliradelc]

Hi,

We found this bug in Opencast*, but after research. I found that the code in paella core also is affected over this potential error.

*Live streaming is not load in Paella 7 because there is no default preview image.

What is the error,

If the media doesn't have videoPreviewand videoPreviewPortrait and is not set in config.json a default value (defaultVideoPreviewPortrait and defaultVideoPreview) paella will fail to load the media.

The potential error is here:

paella-core/src/js/Paella.js

Lines 96 to 100 in a3ef034

	function buildPreview() {
	const preview = (this.videoManifest?.metadata?.preview && resolveResourcePath(this, this.videoManifest?.metadata?.preview)) || this.defaultVideoPreview;
	const previewPortrait = (this.videoManifest?.metadata?.previewPortrait && resolveResourcePath(this, this.videoManifest?.metadata?.previewPortrait)) || this.defaultVideoPreviewPortrait;
	this._previewContainer = new PreviewContainer(this, this._containerElement, preview, previewPortrait);
	}

Suggested fixes:

1. Add a catch to continue with the player load even if the preview image are not available.
2. Add a function to generate a preview SVG file if there is manifest data (Title, author, etc).

I think the two suggestions can be implemented simultaneously. What are your thoughts?

[ferserc1]

As stated in the documentation, this is not a bug, it is the normal behaviour. It is mandatory to always have a preview image, because due to browser security settings, autoplay may not be available, even for live videos.

The first solution you propose is not feasible, because if the browser blocks autoplay, in some situations it can cause usability problems.

As for the second solution, I don't understand why you find this option better than simply defining a default image in the configuration, as the solution you propose also depends on having metadata available, whereas the default preview image always works.

If you are still interested in implementing the second option, you could do so without modifying paella-core, by overriding some of the initialisation functions to provide a data URL in the defaultVideoPreview and defaultVideoPreviewPortrait fields. It is easy to generate an image from text using an HTML Canvas, from which you can get a data URL that you could place in these fields.