I have seen cases when ScriptProcessorNode is causing delays of several (2-3 is quite typical) seconds. To trigger this behavior I set up a ScriptProcessorNode early on in the lifetime of a page, while there's still a lot of other stuff going on on the main thread. I put in some logging in my build to analyse this (logging just before mLatency is increased at [1]): First we see the huge delay that causes us to start dropping frames. > ##### 0x120ef8700 mLatency=0,00000, latency=0,00039 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=-0,00542, latency=2,23579 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=2,22457, latency=0,00068 bufferDuration=0,00580 It starts to catch up. > ##### 0x120ef8700 mLatency=2,21944, latency=0,00122 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=2,21485, latency=0,00059 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=2,20964, latency=0,00046 bufferDuration=0,00580 Eventually we finish dropping frames, but it is prematurely; mLatency is at ~0.5. > ##### 0x120ef8700 mLatency=0,50814, latency=0,00047 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=0,50281, latency=0,00047 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=0,00000, latency=0,00050 bufferDuration=0,00580 We're still catching up with the original latency after the reset. > ##### 0x120ef8700 mLatency=-0,00531, latency=0,00047 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=-0,01064, latency=0,00962 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=-0,00683, latency=0,00050 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=-0,01213, latency=0,00053 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=-0,01740, latency=0,00060 bufferDuration=0,00580 And stabilize at ~ -0.45. This means ~ 0.45 seconds delay for the user. > ##### 0x120ef8700 mLatency=-0,44514, latency=0,00049 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=-0,45045, latency=0,01121 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=-0,44505, latency=0,00048 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=-0,45037, latency=0,01132 bufferDuration=0,00580 > ##### 0x120ef8700 mLatency=-0,44485, latency=0,00051 bufferDuration=0,00580 What happens is: * Huge delay on main thread * Start dropping frames in ScriptProcessorNode.cpp since mLatency > MAX_LATENCY_S * The change from bug 932621 is trigger happy and makes us stop dropping frames prematurely. * The input keeps catching up (causing a delay since we're not dropping the output anymore), but mLatency was reset so mLatency is now going negative - putting the frame dropping logic out of play. [1] https://dxr.mozilla.org/mozilla-central/source/dom/media/webaudio/ScriptProcessorNode.cpp#145

Do you have any clever ideas on how to fix this Paul? Could we perhaps see in the output queue how much has (not) been consumed and thus more reliably know how big the latency is?

(In reply to Andreas Pehrson [:pehrsons] (Telenor) from comment #1) > Could we perhaps see in the output queue how much has (not) been consumed > and thus more reliably know how big the latency is? We could. I have a patch that simplifies the fram-dropping-algorithm a whole lot. I hope there are no holes in it ;-)

/r/7425 - Bug 1157137 - Fix WebAudio ScriptProcessorNode sometimes gaining high latency. r=padenot Pull down this commit: hg pull -r d183fc9db2a5712cc452c341507058ceaf5fa6b5 https://reviewboard-hg.mozilla.org/gecko/

There. Anyone else that should review as well?

Try push: https://treeherder.mozilla.org/#/jobs?repo=try&revision=2f770b09eafd

Try is happy. Some unexpected Android M-6 failures caused me some confusion but they're for 4.3 which is apparently not tested on m-i or m-c.

Comment on attachment 8595901 [details] MozReview Request: bz://1157137/pehrsons https://reviewboard.mozilla.org/r/7423/#review6257

This has been an issue for me for over a year in Firefox on Mac OS X Test url would be my js gba emulator: http://jsemu.github.io/gba/ Pick a game and you'll notice the delay can sometimes be up to a full second, and it's unstable on what buffer level it softens to.

(In reply to Grant Galitz from comment #8) > This has been an issue for me for over a year in Firefox on Mac OS X > > Test url would be my js gba emulator: http://jsemu.github.io/gba/ > Pick a game and you'll notice the delay can sometimes be up to a full > second, and it's unstable on what buffer level it softens to. I tried on my local build of nightly debug with the patch. There were so many things going on on main thread that it was like playing in slow motion more or less (and audio constantly breaking up to that). That could be in part due my debug build perhaps. But good news, no delay! :-)