Content Steering - Pathway Cloning with the same BASE-ID and ID

[burak-kara]

When the pathway cloning is applied with the same BASE-ID and ID, the player fails to select the newly synthesized (from a Pathway Clone object) BaseURL as there are multiple BaseURLs with the same serviceLocation value.

Here, assuming that using the same BASE-ID and ID aligns with the spec https://www.etsi.org/deliver/etsi_ts/103900_103999/103998/01.01.01_60/ts_103998v010101p.pdf.

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: https://www.content-steering.com/bbb/playlist_steering_cloudfront_https.mpd
• Dash.js version: 5.0.1
• Browser name/version: Google Chrome / Version 133.0.6943.141 (Official Build) (64-bit)
• OS name/version: Windows 11 Enterprise / 24H2

Steps to reproduce

• The player requests a DASH Steering Manifest from Steering Server.
• Steering Server includes PATHWAY-CLONES in the DASH Steering Manifest. It uses an existing Service Location identifier for BASE-ID and ID in the Pathway Clone object. Example DASH Steering Manifest response below

{
    "VERSION": 1,
    "TTL": 300,
    "RELOAD-URI": "http://steering-server.com/dash.dscm",
    "PATHWAY-PRIORITY": [
        "cdn-a",
        "cdn-b"
    ],
    "PATHWAY-CLONES": [
        {
            "BASE-ID": "cdn-a",
            "ID": "cdn-a",
            "URI-REPLACEMENT": {
                "HOST": "content.cdn-a.com",
                "PARAMS": {
                    "param": "param"
                }
            }
        }
    ]
}

Observed behavior

• The player applies the pathway cloning and appends the newly synthesized BaseURL to the target BaseURLs list. Then, the available BaseURL list becomes as follows

[
    {
        "url": "content.cdn-a.com",
        "serviceLocation": "cdn-a",
        ...
        "queryParams": {}
    },
    {
        "url": "content.cdn-b.com",
        "serviceLocation": "cdn-b",
        .....
        "queryParams": {}
    },
    {
        "url": "content.cdn-a.com",
        "serviceLocation": "cdn-a",
        ...
        "queryParams": {
            "param": "param"
        }
    },
]

• Later, on

  dash.js/src/streaming/utils/baseUrlResolution/ContentSteeringSelector.js

  Line 85 in f288ab0

  function _findexIndexOfServiceLocation(pathwayPriority = [], baseUrls = []) {

  the player selects the first BaseURL that is extracted from the manifest, not the newly synthesized one.
• The reason is that the player searches for the first occurrence of the elements of PATHWAY-PRIORITY list in the available BaseURLs list.
• It matches pathway-id and serviceLocation values.

Expected behavior

It should select the newly synthesized (from a Pathway Clone object) BaseURL. For this, the player should insert the newly created BaseURL (synthesized BaseURLs) to the beginning of available BaseURLs. Possible fix on

dash.js/src/streaming/models/BaseURLTreeModel.js

Line 128 in f288ab0

targetBaseUrls = targetBaseUrls.concat(synthesizedBaseUrls)

synthesizedBaseUrls= synthesizedBaseUrls.concat(targetBaseUrls)

to have

[
    {
        "url": "content.cdn-a.com",
        "serviceLocation": "cdn-a",
        ...
        "queryParams": {
            "param": "param"
        }
    },
    {
        "url": "content.cdn-a.com",
        "serviceLocation": "cdn-a",
        ...
        "queryParams": {}
    },
    {
        "url": "content.cdn-b.com",
        "serviceLocation": "cdn-b",
        .....
        "queryParams": {}
    },
]

Another fix might be replacing the existing BaseURL in the targetBaseUrls with the newly synthesized one if they have the same serviceLocation.

[dsilhavy]

I would like to check this with DASH-IF. From my understanding, you have two elements with the same serviceLocation now. As you wrote, I think the most reasonable approach would be to replace the existing BaseURL with the newly synthesized one. I want to make sure that this is standard conform, though:

  "BASE-ID": "cdn-a",
  "ID": "cdn-a",

[dsilhavy]

@burak-kara Do you have a reference stream with PATHWAY-CLONES to reproduce the behavior. For the sample stream you pasted above, I don't get any PATHWAY-CLONES.

I think there is also an issue in dash.js with PATHWAY-CLONES and VoD content in general. The available BaseURLs are only updated after a manifest refresh, but not after a new response from the steering server. This means the approach described above would work one time if queryBeforeStart is set to true. For subsequent updates from the steering server the new synthesized elements will probably be missing. Need to validate this with a teststream. If this is confirmed, we can also fix this as part of this PR/issue.

[burak-kara]

Hi @dsilhavy , unfortunately, I don't have a public content steering server deployment that applies the pathway cloning. Sorry for the inconvenience.

I will try to expose a public endpoint so we can validate, but this may take a week or so. In the meantime, I am also testing this with a live profile.

[dsilhavy]

@burak-kara Thanks. I will try to set up a local teststream for validation. Can you please check against #4706. I haven't merged this PR yet, but it should address the two issues you and I described above.

[burak-kara]

Hi @dsilhavy , thank you! LGTM