Console error due to reading field from null

[lamflam]

Environment

• [] The MPD passes the DASH-IF Conformance Tool on https://conformance.dashif.org/
• [] The stream has correct Access-Control-Allow-Origin headers (CORS)
• [] There are no network errors such as 404s in the browser console when trying to play the stream
• [] The issue observed is not mentioned on https://github.com/Dash-Industry-Forum/dash.js/wiki/FAQ
• [] The issue occurs in the latest reference client on http://reference.dashif.org/dash.js/ and not just on my page

• Link to playable MPD file: N/A
• Dash.js version: 4.1.0
• Browser name/version: Chrome Version 94.0.4606.81 (Official Build) (x86_64)
• OS name/version: Mac OS/X

Steps to reproduce

1. Please provide clear steps to reproduce your problem
2. If the bug is intermittent, give a rough frequency if possible

Observed behavior

The player works, but seeing errors in the console.

Console output

Uncaught TypeError: Cannot read properties of null (reading 'end')

Expected behavior

This shouldn't error.

On this line, DVRWindow.end is used but two lines above it can explicitly be set to null. I'm not sure what the expected behavior here is exactly (whether or not null is truly valid) but if so the seek should probably be made conditional on DVRWindow having a value.

dash.js/src/streaming/controllers/PlaybackController.js

Lines 182 to 184 in ef00170

	const DVRWindow = DVRMetrics ? DVRMetrics.range : null;
	seek(DVRWindow.end - mediaPlayerModel.getLiveDelay(), true, false);

[dsilhavy]

@lamflam Thanks for pointing this out. I am curious how you were able to to trigger this error. Are you playing in low latency mode? Can you share the structure of your MPD, for instance is there a timeShiftBufferDepth parameter? Any specific settings you are using?

[dsilhavy]

Issue is addressed in #3789

[lamflam]

Awesome, thanks @dsilhavy!

Yes I am using low latency mode, here are my settings:

{
    streaming: {
        lowLatencyEnabled: true,
        delay: {
            liveDelay: 1.5,
        },
        liveCatchup: {
            enabled: true,
            playbackBufferMin: 0.5,
            mode: 'liveCatchupModeLoLP',
            minDrift: 0.05,
            playbackRate: 0.2,
            latencyThreshold: 30,
        },
    },
}

It actually only seemed to happen when I switch from the one stream to another, never on the first attempt to play a stream. When switching streams, I call reset() on the MediaPlayer and then call initialize() again with the new stream details to start playback. Everything works very well, I just happened to notice the error in the console and when I dug in I noticed that the explicit null reference.

Thanks again for the quick fix! dash.js is an incredible tool :)

[lamflam]

Also, should I close this or do you generally keep it open until it makes it into a public release?

[dsilhavy]

@lamflam Thanks for the feedback, probably the function is called while the switch to the next stream is performed. Please close this issue then, the fix will be part of the next release 4.1.1