Add Listen Mode sample and update samples.json with new entry

[sebastianpiq]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @sebastianpiq, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new sample application that showcases a 'Listen Mode' for alternative media presentations within a DASH stream. This mode allows for flexible insertion of alternative content into a live stream, initially without a fixed duration. The key innovation is the ability to later send a status update to the manifest, dynamically adding a maxDuration attribute to the ReplacePresentation event, which then signals the player to return to the original content. This provides a powerful mechanism for managing dynamic content insertions in live streaming scenarios.

Highlights

• New Sample: Listen Mode for Alternative MPD: Introduces a new sample demonstrating a 'Listen Mode' for alternative media presentations, allowing for dynamic insertion and removal of alternative content in a live DASH stream.
• Dynamic Manifest Modification: The sample showcases how to dynamically modify the Media Presentation Description (MPD) using a response interceptor to insert and update ReplacePresentation events.
• Flexible Content Insertion: Demonstrates the ability to insert alternative content without an initial maxDuration, and then later update the event with a maxDuration (or maxDuration="0") to signal the player to return to the original stream.

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[gemini-code-assist]

Code Review

This pull request introduces a 'Listen Mode' sample for Alternative Media Presentations, which is a valuable addition. The implementation effectively uses a manifest response interceptor to dynamically manage events. My review includes suggestions for improving robustness and maintainability, such as adding input validation for user-provided values, ensuring unique event IDs, removing unused code, and refactoring duplicated logic for event creation. These changes will make the sample more resilient and easier to maintain.

[gemini-code-assist]

The value from the timeOffset input is parsed with parseInt without validation. If a user enters non-numeric text (e.g., 'abc'), parseInt will return NaN. This NaN value is then used to calculate presentationTime, which also becomes NaN, causing the event logic to fail. You should validate the parsed value to ensure it's a number and handle the invalid input case gracefully.

Suggested change

	const timeOffset = parseInt(document.getElementById('timeOffset').value);
	const timeOffset = parseInt(document.getElementById('timeOffset').value, 10);
	if (isNaN(timeOffset)) {
	showStatus('Invalid Time Offset. Please enter a valid number.', 'danger');
	return;
	}

[gemini-code-assist]

The constant DEFAULT_MAX_DURATION is defined but never used in the script. It can be safely removed to improve code clarity.

[gemini-code-assist]

The logic for creating the alternative MPD event is duplicated in updateManifestViewer() (which builds an XML string for display) and addManifestResponseInterceptor() (which builds DOM elements to inject into the manifest). This can lead to inconsistencies if one is updated and the other is not.

Consider refactoring this into a single function that creates the event structure as DOM elements. addManifestResponseInterceptor can then directly use these elements, and updateManifestViewer can serialize and highlight them. This would centralize the event creation logic and improve maintainability.

[gemini-code-assist]

The manifestUrl parameter is passed to the addManifestResponseInterceptor function but it is not used within the function. It can be removed from the function signature and from the call at line 343 to simplify the code.

Suggested change

	function addManifestResponseInterceptor(manifestUrl) {
	function addManifestResponseInterceptor() {

[gemini-code-assist]

The eventId is always assigned the value 0. If the player is reloaded by clicking the button again, a new event will be created with the same ID. While this might work in this specific sample because the old event stream is removed before adding a new one, it's better practice to ensure unique event IDs per the DASH-IF specification. Consider incrementing eventId after each use to guarantee uniqueness.

Suggested change

	id: eventId,
	id: eventId++,