It looks like about 1.2% of Nightly users aren't getting H264: https://telemetry.mozilla.org/new-pipeline/dist.html#!cumulative=0&end_date=2022-05-01&include_spill=0&keys=__none__!__none__!__none__&max_channel_version=nightly%252F101&measure=WEBRTC_H264_ENABLED&min_channel_version=nightly%252F101&processType=*&product=Firefox&sanitize=1&sort_by_value=0&sort_keys=submissions&start_date=2022-04-28&table=0&trim=1&use_submission_date=0

on Windows 7 that jumps to 9.25% of users.

Re-stating what we said on chat.m.o here:

• This might well be because those users are on Windows N or Windows KN. Those version don't have codecs shipped with the OS by default, and a special package has to be installed (the "Media Feature Pack"). We have some code to detect this but it isn't hooked up to telemetry.
• Those versions are (respectively) for the Europeean and South Korean market, we might be able to confirm or infirm this suspicion by looking at the locales.

(In reply to Paul Adenot (:padenot) from comment #1)

Re-stating what we said on chat.m.o here:

• This might well be because those users are on Windows N or Windows KN. Those version don't have codecs shipped with the OS by default, and a special package has to be installed (the "Media Feature Pack"). We have some code to detect this but it isn't hooked up to telemetry.

Just to clarify on this bit -- Is Media Feature Pack a hard requirement for OpenH264 to work? And if so, which aspects of OpenH264 require it?

Asking folks to install the Media Pack just to make a WebRTC call seems burdensome, so it seems worth exploring if it can be removed as a dependency entirely...

The Media Feature Pack should not be needed for OpenH264 to work.

(In reply to Jeff Muizelaar [:jrmuizel] from comment #3)

The Media Feature Pack should not be needed for OpenH264 to work.

If the media pack isn't needed, what is the the significance or takeaway from this statement from :padenot above?

This might well be because those users are on Windows N or Windows KN. Those version don't have codecs shipped with the OS by default, and a special package has to be installed (the "Media Feature Pack"). We have some code to detect this but it isn't hooked up to telemetry.

It was a hypothesis. We don't have any evidence to suggest it's true.