Live Thumbnails in multi-period not displayed as expected

[nicoweilelemental]

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:
  Time+timeline https://d24rwxnt7vw9qb.cloudfront.net/out/v1/6ba06d17f65b4e1cbd1238eaa05c02c1/index.mpd
  Number+timeline https://d24rwxnt7vw9qb.cloudfront.net/out/v1/ee565ea510cb4b4d8df5f48918c3d6dc/index.mpd
• Dash.js version: 4.1.1
• Browser name/version: Chrome 94
• OS name/version: Win10

Steps to reproduce

Just play back one of the two streams and mouseover the seekbar (starting on the live edge as thumbnails in multi-period are initialized only for the last period, for the moment).

Observed behavior

Only one image thumbnail is displayed per period, when moving the cursor over the seekbar.

Console output

No error displayed in the console.

Expected behavior

One image should be displayed every 4 second, when moving the cursor over the seekbar.

Everything is working fine with single period manifests, all image thumbnails are displayed.
Sample single period streams:
Number+duration https://d10gktn8v7end7.cloudfront.net/out/v1/6ee19df3afa24fe190a8ae16c2c88560/index.mpd
Time+timeline https://d10gktn8v7end7.cloudfront.net/out/v1/8c72b60a855c45a0add0864f7ed18404/index.mpd
Number+timeline https://d10gktn8v7end7.cloudfront.net/out/v1/cda20dc2e5e54aee931750c3fa76119c/index.mpd

[dsilhavy]

Thanks for reporting, this requires a redesign of the Thumbnail logic in dash.js. Instead of having an individual ThumbnailController per period we need a global ThumbnailController for the complete stream.

Right now the ThumbnailControllers are initialized once a period is started. This is why thumbnails are only shown for periods that have been played at least once.

[nicoweilelemental]

There is an additional level of problem here, on top of the single ThumbnailController question: in the last period, only one thumbnail is displayed despite moving the cursor above the seekbar, while in the single period steams we can see a discrete thumbnail every 4s, as expected.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. However, it might still be relevant so please leave a short comment if it should remain open. Otherwise the issue will be closed automatically after two weeks. Thank you for your contributions.

[dsilhavy]

unstale

[stale]

This issue has been automatically marked as stale because it has not had recent activity. However, it might still be relevant so please leave a short comment if it should remain open. Otherwise the issue will be closed automatically after two weeks. Thank you for your contributions.

[nicoweilelemental]

unstale

[stale]

This issue has been automatically marked as stale because it has not had recent activity. However, it might still be relevant so please leave a short comment if it should remain open. Otherwise the issue will be closed automatically after two weeks. Thank you for your contributions.

[dsilhavy]

unstale