1246292 - Mismatch between playback speed shown and actual playback speed

Status: RESOLVED INVALID

(Webtools Graveyard :: Air Mozilla, defect)

Description

[Gene Wood [:gene]]

There seems to be a bug where the playback of a recorded air mozilla recording can end up in a state where the playback speed and the displayed rabbit playback speed do not match. This mismatch is often reproducible but not 100% consistent so it may take some fiddling with to reproduce the problem

First a baseline :

Start a video
set speed to 1x
watch for 15 seconds
change to a different tab in Firefox and continue listening to the video playing in the other tab
stay in the new non-air-mozilla tab for 30 seconds
change back to the air mozilla tab and the video will still be playing at 1x

This is to be expected and not very exciting.

Now, try this with a speed change

Start a video
set speed to 1.5x
watch for 15 seconds
change to a different tab in Firefox and continue listening to the video playing in the other tab
stay in the new non-air-mozilla tab for 30 seconds
At some point the speed of playback will return to 1x which you'll be able to hear as the audio will go back to a normal speed. You won't be able to see it because you'll be in a different tab
change back to the air mozilla tab and the video will still be playing at 1x but the selector at the bottom of the page will still say 1.5x
change the speed from 1.5x to 1x and you'll find that the video is now actually playing at a speed slower than 1x (e.g. 0.5x)

The behavior is also complicated by the fact that it appears that some of your speed selection is captured in the cached video content in that if you set the speed to 1x, skip the video back a minute and play it the video will continue playing at 0.5x (1x displayed). I don't fully understand what's going on here but wanted to mention that there's some stickiness to the behavior that I'm guessing relates to caching.

The video that I saw this in is

https://air.mozilla.org/mozlando-opening-session/

Comment 1

[Peter Bengtsson [:peterbe]]

Interesting. And annoying. 
We use JWPlayer6 to play html5 videos but the change of playback speed is "beyond" JWPlayer and a native html5 effect we apply on the underlying <video> element.

But it's certainly stinky that the playback rate "suddenly" changes in a tab you're not clicking on things in :(
That sounds like a Firefox core media bug. 

What we can start with is correct the UX so that if it happens the little iconography matches up at least. I just found out there's a `ratechanged` event we can listen to. 
https://developer.mozilla.org/en-US/Apps/Build/Audio_and_video_delivery/WebAudio_playbackRate_explained

Comment 2

[Peter Bengtsson [:peterbe]]

Attachment: Link to Github pull-request: https://github.com/mozilla/airmozilla/pull/615

This patch will only very partially "solve" the problem. 

It used to be that that highlighting (which rate you current play at) was based on where you clicked. Now, instead, there's an event handler that determines that. So the clicking will only *set* the rate and not worry about reflecting that. 

Also, I tried several times and I could not reproduce the spontaneous change-of-rate in Fx 46.0a2 (Dev edition). So we'll have to keep an eye on it.

Comment 3

[[github robot]]

Commits pushed to master at https://github.com/mozilla/airmozilla

https://github.com/mozilla/airmozilla/commit/da29f7db63e642e400f274bf50b7f88933b6e22a
bug 1246292 - update playbackrate by event

https://github.com/mozilla/airmozilla/commit/3b530a70b685ce529960694ea4a3cd97cf75dc40
Merge pull request #615 from peterbe/bug-1246292-update-playbackrate-by-event

bug 1246292 - update playbackrate by event

Comment 4

[Peter Bengtsson [:peterbe]]

Have you ever seen this happen since?
By the way, we recently switch to JWPLayer 7 which is vastly different from JW Player 6 which we had before.

Comment 5

[Gene Wood [:gene]]

I haven't watched an airmo recording since unfortunately.

Comment 6

[Andy Kochendorfer]

Platform deprecated.