Bug 190963 – On mobile Safari, mp3 audio spikes in volume after resuming from paused state

• Status: NEW
• Component: Web Audio

I have a tag that I have loaded an mp3 into. When I play the mp3 when it is in paused state, the volume on iPad spikes much louder for a few seconds before returning to its prior volume level. The issue occurs in this sequence:

var sound = $("#AudioElement")[0];
sound.src = url;
sound.load();

// Later
sound.pause();

// Later
sound.play();

I have reproduced this on iOS 11.2.5, 12.0, and 12.1.

The mp3s are encoded at 64Kbps/44100Hz in CBR formatting.

I think 1 of two things is happening here:

1. The audio when first played is being muted by Safari for some reason, and resuming the audio from paused state causes the volume to spike up to the global volume control for the device. IE, volume is spiking to what its supposed to be before being muted again by Safari.

or 

2. The volume is not being muted by Safari on first play, and the spike in volume is just abnormal.

[Radar WebKit Bug Importer]

<rdar://problem/45656195>

Jer Noble, I've noticed you've been assigned to this case as well. You can use the same login to the demo account I got for you in the other bug (190644) to reproduce. Select the same assessment from the menu and click the pause button in the lower left.

If possible, could I an update on this ticket, please?

I have tried a few workarounds to this issue, re-encoding the MP3s to different sample and bit rates. Here are the set of encodings I've tried (sample rate/bit rate):
20Kbps/11025
24Kbps/22050
32Kbps/22050
48Kbps/41000
56Kbps/44100
64Kbps/44100
80Kbps/44100
96Kbps/44100
112Kbps/44100
128Kbps/44100

I have also tried wavs encoded at 44100 bit rate. 

None of these resolved the issue. I am at loss for what else I can do different. And advice or help would be greatly appreciated.