Re: [mediacapture-main] Should we revisit and document getUserMedia() track order? (#1028)

Just for fun, I found the git commit that added getTracks().

commit 1149581cc2c4dd236470b7a661f1850cf091c7a4
Author: Adam Bergkvist <adam.bergkvist@ericsson.com>
Date:   Wed Jun 4 10:15:19 2014 +0200

    Bug 25860: make sure we have a bug to have a getTracks that gives you all the tracks

The very first instantiation of this function had the "order is user agent defined and doesn't have to be stable" language.
I can't find any mailing list discussion on this topic, but this is the kind of language we ended up with when there was no consensus on a rule to impose. Someone with the patience to search the 2014 meeting minutes may find more.

The Chrome implementation (https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/modules/mediastream/media_stream.cc;drc=5b1ceafef667af5fa64c3002e9427ddf01e105a1;l=291) is *literally* "first take all the audio tracks, and then all the video tracks" - due to a Blink reformat, I can't see its history beyond 2016, but it's been unchanged since that time.

"User needs come before the needs of web page authors, which come before the needs of user agent implementors, which come before the needs of specification writers, which come before theoretical purity."

For Chrome-as-a-product, changing this behavior risks hurting users (those using software that was working fine on earlier versions, and may no longer be maintained, but suddenly stops working). In addition, changing the spec harms web page authors that actually believe the spec to reflect realilty until the time such a behavior change can be agreed to and experimented with to the degree that one can have evidence of absence of harm rather than absence of evidence of harm.

For Chrome, no benefit has been demonstrated. A "theoretical purity" argument carries very little weight.


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Received on Wednesday, 26 February 2025 07:39:10 UTC