Bug 208233

Summary: Audio crackling in WebRTC calls on iOS using Cisco Meeting WebRTC app
Product: WebKit Reporter: mawojtcz
Component: WebRTCAssignee: Nobody <webkit-unassigned>
Status: RESOLVED CONFIGURATION CHANGED    
Severity: Critical CC: milen.yordanov, webkit-bug-importer, willwoo, youennf
Priority: P2 Keywords: InRadar
Version: Safari 13   
Hardware: iPhone / iPad   
OS: iOS 13   

Description mawojtcz 2020-02-26 03:16:58 PST 
When joining calls using Cisco Meeting WebRTC app in Safari on iPhones the user can hear audio crackling. The crackling is heard on different iPhone models (for example: 7s, XR) and different iOS versions (both 12.x and 13.x)

Here at Cisco, we have created a temporary account in our product that should allow you to replicate the issue we are seeing. I can provide you a link to it if you message me privately, as we don't want this link to be available in public.

We've done some initial investigation on this and these are our findings:
- Audio plays fine in our product without any crackling in Chrome and Firefox on Windows and MacOS as well as Safari on MacOS and Chrome on Android
- The issue is intermittent. Sometimes the audio may work fine for a long period of time and on another occasion the crackling will be very frequent. It seems that the probability of crackling gets higher with longer time since the phone's reboot or when more apps have been used. Once it starts, it seems to be worse when the app is doing some UI transitions etc.
- When we capture the network traffic and recreate the audio from the pcap file, we don't hear the crackling in the resultant wav file
- When we've modified our werbtc app to not do any video encoding and decoding, we could still hear the audio crackling
- Audio crackling can be heard also when we tried other audio codecs
Comment 1 Radar WebKit Bug Importer 2020-02-26 05:26:27 PST 
<rdar://problem/59802870>
Comment 2 youenn fablet 2020-04-17 09:53:17 PDT 
bug 210107, bug 209969, bug 210052, and bug 210180 are helping reducing the audio crackling according our testing.
If the device is doing intensive processing, there might still be some audio drop outs. This might also happen when page is scrolling, given the WebRTC audio thread priority is the same as the scrolling one.

Closing the bug based on above bugs being fixed.
Comment 3 youenn fablet 2020-05-19 04:17:52 PDT 
https://bugs.webkit.org/show_bug.cgi?id=211720 will also help removing audio crackling when piping a media stream into WebAudio.
Comment 4 youenn fablet 2020-05-20 10:48:39 PDT 
https://bugs.webkit.org/show_bug.cgi?id=212132 is another one that will help in case web audio is used to analyse media streams