Fatal playback failure due to phantom media segment request

[romsil]

Have you read the FAQ and checked for duplicate open issues?
Yes

What version of Shaka Player are you using?
3.2.0

Can you reproduce the issue with our latest release version?
Yes

Can you reproduce the issue with the latest code from master?
Yes

Are you using the demo app or your own custom app?
Custom app.

If custom app, can you reproduce the issue using our demo app?
I believe so. It is difficult to reproduce the issue since it only happens on certain ads on our player.

What browser and OS are you using?
Chrome, macOS

For embedded devices (smart TVs, etc.), what model and firmware version are you using?
N/A

What are the manifest and license server URIs?
Our manifest URIs are short-lived, so I am pasting the period declaration instead:

<Period duration="PT30.720000S" id="a-2">
      <AssetIdentifier schemeIdUri="urn:com:uplynk:ad-asset-id" value="d4bfa4522c044a968fc4f2a0d944340f" />
      <AdaptationSet audioSamplingRate="48000" contentType="audio" group="1" lang="en" mimeType="audio/mp4" segmentAlignment="true" startWithSAP="1">
         <Role schemeIdUri="urn:mpeg:dash:role:2011" value="main" />
         <Representation bandwidth="127878" codecs="mp4a.40.5" id="v0">
            <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2" />
            <BaseURL>https://RedactedCDNUrl/slices/d4b/4f59ea65df184a2580ad8fc80d3eaa32/d4bfa4522c044a968fc4f2a0d944340f/</BaseURL>
            <SegmentTemplate duration="184320" initialization="https://RedactedCDNUrl/slices/d4b/4f59ea65df184a2580ad8fc80d3eaa32/d4bfa4522c044a968fc4f2a0d944340f/TK_init.mp4" media="TK_$Number%08d$.m4f" startNumber="0" timescale="90000" />
         </Representation>
      </AdaptationSet>

See notes below on our investigation results.

What configuration are you using? What is the output of player.getConfiguration()?
Mostly default. See attached screenshot for player.getConfiguration() output:

What did you do?
I just let the asset play until it reaches the ad period.

What did you expect to happen?
Playback will continue with no fatal error.

What actually happened?
Shaka makes a network request to media segment TK_00000015.m4f.
Based on the period declaration for the audio Adaptation Set, the media segments from TK_00000000.m4f to TK_00000014.m4f should have been enough. See attached screenshot of my computation.

We investigated the issue and we think this is caused by small floating points being ceiled in Shaka. We have patched Shaka below to fix the issue.

--- a/lib/dash/segment_template.js
+++ b/lib/dash/segment_template.js
@@ -345,7 +345,7 @@ shaka.dash.SegmentTemplate = class {
       // In period-relative positions (0-based).
       const availablePeriodPositions = [
         Math.ceil(availablePeriodTimes[0] / segmentDuration),
-        Math.ceil(availablePeriodTimes[1] / segmentDuration) - 1,
+        Math.ceil((availablePeriodTimes[1] / segmentDuration).toFixed(10)) - 1,
       ];

It's a small one-line fix but it's causing playback failure.

[michellezhuogg]

Hello @romsil , thank you for finding the root cause! Would you like to send us a Pull Request?

[romsil]

@michellezhuogg Yes. I'm now looking into https://github.com/google/shaka-player/blob/master/CONTRIBUTING.md :)

[romsil]

@michellezhuogg I just submitted the pull request: #3721

Thank you.

[romsil]

Just an addendum:

Before the fix above, the actual values that we get on Chrome are:

availablePeriodTimes[1] = 30.720000000000027,
segmentDuration = 2.048,
availablePeriodTimes[1] / segmentDuration = 15.000000000000012
Math.ceil(availablePeriodTimes[1] / segmentDuration) = 16

After the fix, we get:

Math.ceil(availablePeriodTimes[1] / segmentDuration).toFixed(10) = 15

[michellezhuogg]

Thank you!

[boredom2]

Hi there,

as Shaka v3.3 is now initially released, this Problem here would be our biggest issue.
As far as I can see, this has not been included in the 3.3 Release, right?
When can we expect this to be merged into a Release?

Thank you very much and btw - Happy New Year :)

[joeyparrish]

This issue has not been fixed yet. The fix in PR #3721 was not merged due to some debate that was never resolved. I'll give it another look now.