CMCD reporting sample players shows the CMCD version field even though it's not sent (CMCD_DATA_GENERATED event is misleading)

[mgreve-akamai]

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: Irrelevant
• Dash.js version: Newest nightly on Aug 25, 2021 (https://reference.dashif.org/dash.js/nightly/dist/dash.all.debug.js)
• Browser name/version: Irrelevant
• OS name/version: Irrelevant

Steps to reproduce

• Play the stream on the CMCD sample page: https://reference.dashif.org/dash.js/nightly/samples/advanced/cmcd.html

Observed behavior

The player shows the CMCD version field in the text area on the page, but dash.js is not sending the field as part of requests (as expected).

Expected behavior

I would expect the textarea on the page to show the fields that are sent on the request, and not be misleading. Hence, it should not show the version (v) field.

FYI - it is correct behaviour to omit the version field if it's 1.

Quote from the spec: "The version of this specification used for
interpreting the defined key names and values. If
this key is omitted, the client and server MUST
interpret the values as being defined by version 1.
Client SHOULD omit this field if the version is 1. "

Link to spec: https://cdn.cta.tech/cta/media/media/resources/standards/pdfs/cta-5004-final.pdf

[mgreve-akamai]

I believe this happens because the CMCD_DATA_GENERATED event contains misleading data. The dash.js code modifies the CMCD request in _buildFinalString (e.g. by removing the version field if the value is 1), but the event contains also the data before modification from _getCmcdData.

` if (settings.get().streaming.cmcd && settings.get().streaming.cmcd.enabled) {
const cmcdData = _getCmcdData(request);
const finalPayloadString = _buildFinalString(cmcdData);

            eventBus.trigger(MetricsReportingEvents.CMCD_DATA_GENERATED, {
                url: request.url,
                mediaType: request.mediaType,
                cmcdData,
                cmcdString: finalPayloadString
            });`

Source: https://github.com/Dash-Industry-Forum/dash.js/blob/development/src/streaming/models/CmcdModel.js

[dsilhavy]

Fixed in #3745