ContentSteering promise is resolved too late for fetching of dash initialisation segment

[gmcgarry]

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

If the problem is related to FairPlay, have you read the tutorial?

No

What version of Shaka Player are you using?

Git Commit SHA: d5eab12

Can you reproduce the issue with our latest release version?
YEs.

Can you reproduce the issue with the latest code from main?
Yes.

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

If custom app, can you reproduce the issue using our demo app?
Yes.

What browser and OS are you using?
Safari on MacOS, Chrome on WIndows11

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

What are the manifest and license server URIs?

https://chromium.dolby.link/content_steering/manifest.mpd

What configuration are you using? What is the output of player.getNonDefaultConfiguration()?

{
    \"drm\": {
        \"advanced\": {
            \"com.widevine.alpha\": {
                \"distinctiveIdentifierRequired\": false,
                \"persistentStateRequired\": false,
                \"sessionType\": \"\",
                \"serverCertificateUri\": \"\",
                \"individualizationServer\": \"\"
            },
            \"com.microsoft.playready\": {
                \"distinctiveIdentifierRequired\": false,
                \"persistentStateRequired\": false,
                \"sessionType\": \"\",
                \"serverCertificateUri\": \"\",
                \"individualizationServer\": \"\"
            },
            \"com.microsoft.playready.recommendation\": {
                \"distinctiveIdentifierRequired\": false,
                \"persistentStateRequired\": false,
                \"sessionType\": \"\",
                \"serverCertificateUri\": \"\",
                \"individualizationServer\": \"\"
            },
            \"com.apple.fps\": {
                \"distinctiveIdentifierRequired\": false,
                \"persistentStateRequired\": false,
                \"sessionType\": \"\",
                \"serverCertificateUri\": \"https://ott.dolby.com/OnDelKits/fairplay.cer\",
                \"individualizationServer\": \"\"
            },
            \"org.w3.clearkey\": {
                \"distinctiveIdentifierRequired\": false,
                \"persistentStateRequired\": false,
                \"sessionType\": \"\",
                \"serverCertificateUri\": \"\",
                \"individualizationServer\": \"\"
            }
        },
        \"keySystemsMapping\": {
            \"com.microsoft.playready\": \"com.microsoft.playready.recommendation\"
        }
    },
    \"preferredAudioLanguage\": \"en-AU\",
    \"preferredTextLanguage\": \"en-AU\",
    \"preferredVideoCodecs\": [
        \"dvh1\",
        \"dvhe\"
    ]
}

What did you do?

https://shaka-player-demo.appspot.com/demo/#audiolang=en-AU;textlang=en-AU;uilang=en-AU;assetBase64=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;panel=HOME;build=uncompiled

What did you expect to happen?
This manifest contains a ContentSteering element with an out-of-service defaultServiceLocation, but also contains queryBeforeStart=true. The expected behaviour is that the player will fetch the content-steering response and update the list of service locations and priorities before attempting to fetch the initialisation segment.

What actually happened?

The segment uris for the initialisation segment is constructed before the promise to fetch the content-steering response is resolved. So the initialisation segment is fetched from the out-of-service default service location.
Additionally, timed-out fetches are not causing re-tries on the updated service locations. To be fair, failover may work if the fetches of the initialisation segment received 4xx responses rather than no response. I didn't check.

Are you planning to send a PR to fix it?

The solution is to resolve contentSteeringPromise before passing getBaseUris to DashParser.parsePeriods_().

diff --git a/lib/dash/dash_parser.js b/lib/dash/dash_parser.js
index 66443c343..e92ed2300 100644
--- a/lib/dash/dash_parser.js
+++ b/lib/dash/dash_parser.js
@@ -771,6 +771,8 @@ shaka.dash.DashParser = class {
       urlParams: () => '',
     };
 
+    await contentSteeringPromise;
+
     this.gapCount_ = 0;
     const periodsAndDuration = this.parsePeriods_(
         context, getBaseUris, mpd, /* newPeriod= */ false);
@@ -794,8 +796,6 @@ shaka.dash.DashParser = class {
       presentationTimeline.assertIsValid();
     }
 
-    await contentSteeringPromise;
-
     if (this.isLowLatency_ && this.lowLatencyMode_) {
       const presentationDelay = suggestedPresentationDelay != null ?
           suggestedPresentationDelay : this.config_.defaultPresentationDelay;