Web Audio API weirdness on iOS

I told you about how I’m using the Web Audio API on The Session to generate synthesised audio of each tune setting. I also said:

Except for some weirdness on iOS that I had to fix.

Here’s that weirdness…

Let me start by saying that this isn’t anything to do with requiring a user interaction (the Web Audio API insists on some kind of user interaction to prevent developers from having auto-playing sound on websites). All of my code related to the Web Audio API is inside a click event handler. This is a different kind of weirdness.

First of all, I noticed that if you pressed play on the audio player when your iOS device is on mute, then you don’t hear any audio. Seems logical, right? Except if using the same device, still set to mute, you press play on a video or audio element, the sound plays just fine. You can confirm this by going to Huffduffer and pressing play on any of the audio elements there, even when your iOS device is set on mute.

So it seems that iOS has different criteria for the Web Audio API than it does for audio or video. Except it isn’t quite that straightforward.

On some pages of The Session, as well as the audio player for tunes (using the Web Audio API) there are also embedded YouTube videos (using the video element). Press play on the audio player; no sound. Press play on the YouTube video; you get sound. Now go back to the audio player and suddenly you do get sound!

It’s almost like playing a video or audio element “kicks” the browser into realising it should be playing the sound from the Web Audio API too.

This was happening on iOS devices set to mute, but I was also getting reports of it happening on devices with the sound on. But it’s that annoyingly intermittent kind of bug that’s really hard to reproduce consistently. Sometimes the sound doesn’t play. Sometimes it does.

Following my theory that the browser needs a “kick” to get into the right frame of mind for the Web Audio API, I resorted to a messy little hack.

In the event handler for the audio player, I generate the “kick” by playing a second of silence using the JavaScript equivalent of the audio element:

var audio = new Audio('1-second-of-silence.mp3');
audio.play();

I’m not proud of that. It’s so hacky that I’ve even wrapped the code in some user-agent sniffing on the server, and I never do user-agent sniffing!

Still, if you ever find yourself getting weird but inconsistent behaviour on iOS using the Web Audio API, this nasty little hack could help.

Update: Time to remove this workaround. Mobile Safari has been updated.

abc to SVG | CSS-Tricks

Aw, this is so nice! Chris points to the way that The Session generates sheet music from abc text:

The SVG conversion is made possible entirely in JavaScript by an open source library. That’s the progressive enhancement part. Store and ship the basic format, and let the browser enhance the experience, if it can (it can).

Here’s another way of thinking of it: I was contacted by a blind user of The Session who hadn’t come across abc notation before. Once they realised how it worked, they said it was like having alt text for sheet music! 🤯

WebKit Features in Safari 17.4 | WebKit

It’s a shame that the newest Safari release is overshadowed by Apple’s shenanigans and subsequent U-turn because there’s some great stuff in there.

I really like what they’re doing with web apps added to the dock:

Safari adds support for the shortcuts manifest member on macOS Sonoma. This gives you a mechanism in the manifest file for defining custom menu commands that will appear in the File menu and the Dock context menu.

Web Push on iOS - 1 year anniversary - Webventures

Web Push on iOS is nearing its one year anniversary. It’s still mostly useless.

Sad, but true. And here’s why:

On iOS, for a website to be able to ask the user to grant the push notification permission, it needs to be installed to the home screen.

No other browser on any of the other platforms requires you to install a website for it to be able to send push notifications.

Apple is within their rights to withhold Web Push to installed apps. One could argue it’s not even an unreasonable policy - if Apple made installing a web app at least moderately straightforward. As it is, they have buried it and hidden important functionality behind it.

I really, really hope that the Safari team are reading this.

The Biggest Thing from WWDC 2022 - Webventures

Web Push on iOS will change the “we need to build a native app” decision.

I agree.

Push notifications are definitely not the sole reason to go native, but in my experience, it’s one of the first things clients ask for. They may very well be the thing that pushes your client over the edge and forces them, you and the entire project to accept the logic of the app store model.

Introducing Opportunities & Experiments: Taking the Guesswork out of Performance - WebPageTest Blog

WebPageTest just got even better! Now you can mimic the results of what would’ve previously required actually shipping, like adding third-party scripts, switching from a client-rendered to a server-rendered architecture and other changes that could potentially have a big effect on performance. Now you can run an experiment to get the results before actual implementation.