Reference Player with LL Mode is not playing on the live edge

[huseyinunified]

• The MPD passes the DASH-IF Conformance Tool on https://conformance.dashif.org/
  No, result is below;
  Start MPD validation

====================

Line:Col[14:31]:cvc-complex-type.2.4.a: Invalid content was found starting with element 'ServiceDescription'. One of '{"urn:mpeg:dash:schema:mpd:2011":ProgramInformation, "urn:mpeg:dash:schema:mpd:2011":BaseURL, "urn:mpeg:dash:schema:mpd:2011":Location, "urn:mpeg:dash:schema:mpd:2011":Period}' is expected.

MPD validation not successful - DASH is not valid!

• 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: https://live.unified-streaming.com/scte35/scte35.isml/.mpd
• Dash.js version: 3.0.1 and 3.0.0
• Browser name/version: Firefox 71 and Chrome Version 79.0.3945.88 (Official Build) (64-bit)
• OS name/version: macOS Mojave 10.14.6

Steps to reproduce

1. Use the Reference Player version 3.0.0 and enable Low Latency Mode from the options.
2. Use the Reference Player version 3.0.1, no need to change the default settings.
3. Load the manifest file

Observed behaviour

1. When LL Mode is enabled stream does not start from the live edge. It goes an earlier point of the archive. But if you remove the LL Mode Option and load the manifest again, it starts playing from the live edge.
2. The stream has ServiceDescription which works with LL Mode without need the LL Mode option is checked. So behavior is the same, it starts playing some point in the past. But there is no chance to take it back like 3.0.0. So 3.0.1 never starts playing on the live edge.

[thehusmin]

Hi,

Could you please provide an update about the status and why it is unassigned?

Thanks!

[dsilhavy]

Hi @thehusmin ,
the developer who was looking into this is not longer working on dash.js. We will try to look into it in one of the next sprints.

[dsilhavy]

@thehusmin : In your MPD the @minBufferTime is set to 10seconds while the target latency is set to 2seconds and your minimum latency is 1second. I think @minBufferTime should be equal or less than your minimum latency.

[dsilhavy]

@thehusmin I made some changes to the segment request logic, can you please check against the latest nightly build: https://reference.dashif.org/dash.js/nightly/samples/dash-if-reference-player/index.html

[thehusmin]

Hi @dsilhavy, I've checked the stream and start time looks correct.

But the stream does not play as expected that it's having glitches. I tested the same stream with version 3.0.3 and it plays without glitches.

[dsilhavy]

@thehusmin In my tests the glitches are caused by the target latency. The maximum latency is set to 6sec which seems to result in frequent buffer underruns. 3.0.3 plays 300seconds behind live edge, so the buffer is never empty.

[dsilhavy]

@thehusmin Do you confirm that the changes in the nightly player fix the problem? As described before, low latency playback results in small buffer and potential buffer underruns.

[dsilhavy]

Problem with starttime has been fixed in #3217