1367950 - Don't throttle playback unless the network is "fast", rather than unless we've hit "canplaythrough"

Status: RESOLVED FIXED

(Core :: Audio/Video: Playback, enhancement, P1)

Description

[Chris Pearce [:cpearce (Not reading bugmail)]]

I'm not satisfied with the work in 1364001, so I'm taking it upon myself to satisfy myself.

My concern is that people with slow connections will suffer from "buffering anxiety", and will in fact want to buffer the entire resource, irrespective of the "canplaythrough" state. i.e., they won't want the download to stop part way through once we've downloaded enough that our canplaythrough logic thinks the remaining part of the file can be played without needing to stop to buffer. Users on slow connections are more likely to want to download the entire resource, even if that may not be strictly necessary.

That is certainly what I have wanted in the past when I have had trouble with a slow connection.

So I think we should change so that we only throttle the download when we hit the readahead limit on desktop only when the connection is fast enough that the user is unlikely to have buffering anxiety. I don't think we should use the canplaythrough logic to gate throttling.

Also, we should not be changing the behaviour of Firefox for Android here; on Android the calculus is different as typically data connections are metered and battery life is also an issue. So we should revert to the old behaviour of throttling when the readahead limit is hit irrespective of the network speed/canplaythrough state on mobile.

Comment 1

[Chris Pearce [:cpearce (Not reading bugmail)]]

Attachment: Bug 1367950 - Only throttle download of src=url video if the download is 'fast' on desktop.

Our canplaythrough logic is opaque to the users, so I expect that our recent
change to throttle when we hit the readahead limit would be confusing to users;
those on a slow connection would want their media to prebuffer, and not expect
the download to stop part way through.  They would think that Firefox had
stalled at an arbitrary point for some unknown reason, i.e., they'd think
Firefox was broken. So I think we're better to instead only throttle if the
network is good enough that the user probably doesn't worry about the download
not keeping up with playback.

We should restore the previous behaviour on mobile of throttling when the
download reached the readaheadd limit regardless of canplaythrough or network
speed, as the calculus is different on mobile; the user may also be concerned
about battery life, or hitting their data cap. And often the faster the
cellular network is, the more expensive data on it is.

So this patch changes us to throttle when we reach the readahead limit only if
the network is fast, where fast is defined as being able to stream at twice the
rate estimated to be required to playback without stalling.

It also adds a pref to revert to the old behaviour of not considering the
network speed, which we enable on mobile to restore it to its previous
behaviour.

Review commit: https://reviewboard.mozilla.org/r/143054/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/143054/

Comment 2

[JW Wang [:jwwang] [:jw_wang]]

Comment on attachment 8871573 [details]
Bug 1367950 - Only throttle download of src=url video if the download is 'fast' on desktop.

https://reviewboard.mozilla.org/r/143054/#review146804

It is hard to assume the user intention for best user experience. Without throttling, we will bring bug 1347174 back where user on slow connection will wait for the entire file to be buffered which however will never happen due to the limited cache size and all bandwidth in the end is wasted in downloading and discarding data (see bug 1347174 comment 10 for the detail). We need to figure out a way to solve bug 1347174 correctly.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/b597ea8f9bb4
Only throttle download of src=url video if the download is 'fast' on desktop. r=jwwang

Comment 4

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/b597ea8f9bb4