871431 - [A/V] Background music playback is jittered while browsing

Status: RESOLVED FIXED

(Firefox OS Graveyard :: General, defect, P1)

Description

[leo.bugzilla.gecko]

Start music application -> play any mp3 file -> home button -> start browser -> visit any url -> zooming while it loads web page

Then BGM is jittered.
If you visit the page that has lot of media, it can easily reproduced.

Build ID : 20130503155504
Gaia : 5cbb19e4bb78a7ad879fbe4b9a841e1c35714f5c
Gecko : 950b402b6188bb2f3ce3176e620ed5249719d720

Comment 1

[Lukas Blakk [:lsblakk] use ?needinfo]

Adding qawanted to add this to test plans - trying to listen to music while browsing the web on media-heavy sites.

Comment 2

[Deepa Subramanian]

There is jittering experienced when visiting any url and zoomed while the web page still loading. 
Also, the user is also unable to increase the volume when a headset is used for listening to songs. 

Reproduces 3/8 times on Leo 
Build ID: 20130510070207
Gecko: http://hg.mozilla.org/releases/mozilla-b2g18/rev/2aba3b5ac1c2
Gaia: fcaa90923894211c19b3544b5cb16eb0db5a6286

Comment 3

[David Flanagan [:djf]]

This is not related to the Video app so changing the component.

Deepa: you should probably report the headphone issue as a separate bug.

Leo: What does BGM mean?

Comment 4

[Deepa Subramanian]

> Deepa: you should probably report the headphone issue as a separate bug.
David there is a bug on it already. https://bugzilla.mozilla.org/show_bug.cgi?id=870894

Comment 5

[leo.bugzilla.gecko]

(In reply to David Flanagan [:djf] from comment #3)

> Leo: What does BGM mean?

Sorry, for confusing.
BGM means Back Ground Music.
(Start music application -> play any mp3 file -> home button)

Comment 6

[leo.bugzilla.gecko]

According to my investigation, audio flinger cannot receive any audio buffer to be rendered.
If you check the log, you can find log line like below.
05-09 17:10:05.050 V/AudioFlinger(  893): getNextBuffer() no more data for track 4097 on thread 0x191f248

At that point, CPU usage is over 80% (B2G + plugin container)

Comment 7

[Marco Chen [:mchen]]

Hi,

I found some info related to this issue.

  1. music app in background on playing will be on BACKGROUND_PERCEIVABLE priority.
  2. BACKGROUND_PERCEIVABLE priority will get nice value 10.
  3. B2G process and browser app is under foreground priority and nice value will be 0 & 1

It seems to that B2G process & browser are busy on rendering action and occupy much cpu slots, then the remaining cpu slot is not enough for music app even rendering may occupy 80% but their's high nice value take the cpu slot from music app when it trys to do decoding.

If I set music app to nice value 1 then this bug is gone.

Comment 8

[Justin Lebar (not reading bugmail)]

> If I set music app to nice value 1 then this bug is gone.

What's the highest niceness value you can set the music app to without causing this bug?

We're faced with some hard trade-offs here, because if we increase the priority of the music app, we're decreasing the smoothness of scrolling and other operations in the foreground app.  But I'd be up for giving the music app more CPU.

Comment 9

[Marco Chen [:mchen]]

(In reply to Justin Lebar [:jlebar] from comment #8)
> What's the highest niceness value you can set the music app to without
> causing this bug?
> 

After the testing, set background_perceivable to 7 can avoid this issue but 8.

Hi Leo,

May be you can have a test on your side? Thanks.

http://mxr.mozilla.org/mozilla-central/source/b2g/app/b2g.js#596

Comment 10

[leo.bugzilla.gecko]

(In reply to Marco Chen [:mchen] from comment #9)
> After the testing, set background_perceivable to 7 can avoid this issue but
> 8.
> 
> Hi Leo,
> 
> May be you can have a test on your side? Thanks.
> 

When it's 8, I got some jittering 1~2 times for 15 minutes web surfing.
However the jittering is for a moment. So it doesn't bother me.

Comment 11

[Marco Chen [:mchen]]

(In reply to leo.bugzilla.gecko from comment #10)
> (In reply to Marco Chen [:mchen] from comment #9)
> When it's 8, I got some jittering 1~2 times for 15 minutes web surfing.

Yes, the nice value 8 will still have jitter issue but 7 can avoid it at all on this test case.

Comment 12

[Marco Chen [:mchen]]

Attachment: Modify_Nice_To_7 v1

Based on comment 8, the nice value 7 can avoid this issue so have a patch on this change.

Could you review it or any other suggestion?
Thanks.

Comment 13

[Justin Lebar (not reading bugmail)]

Comment on attachment 749715 [details] [diff] [review]
Modify_Nice_To_7 v1

Okay, this sounds fine.

Comment 14

[Marco Chen [:mchen]]

https://tbpl.mozilla.org/?tree=Try&rev=c626b42ce39f

Comment 15

[Marco Chen [:mchen]]

Attachment: Modify_Nice_To_7 Checkin Version

Add reviewer and approval for leo.

Comment 16

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/projects/birch/rev/8e524063308f

Comment 17

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/8e524063308f

Comment 18

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-b2g18/rev/66f95939ca61

Comment 19

[Marco Chen [:mchen]]

Bug Description:
  When user scrolls the screen on a big page then user will hear audio is jitter.

User Impact:
  When this bug is happened, it degrades user experience on music playback.

Side Effect:
  To raise the nice of background perceivable process may affect the performance of foreground process. But currently foreground's nice value (1) is still more bigger then background perceivable (7).

Comment 20

[Jason Smith [:jsmith]]

This is currently a leo+. This still stands as a wontfix unless this gets a tef+. If you want consideration for tef, please nom.

If it's possible to reproduce this on 1.01, then set this to affected. If we don't know, then we need to nom and set to ?.

Comment 21

[Marco Chen [:mchen]]

Bug Description:
  When user scrolls the screen on a big page in the browser then user will hear audio played by music app in the background is jitter.

User Impact:
  When this bug is happened, it degrades user experience on music playback.

Side Effect:
  To raise the nice of background perceivable process may affect the performance of foreground process. But currently foreground's nice value (1) is still more bigger then background perceivable (7).

Comment 22

[Alex Keybl [:akeybl]]

Daniel - no strong opinion here, up to you.

Comment 23

[Daniel Coloma:dcoloma]

Not blocking, changing process priority at this stage seems to me very risky