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This is very, very cool; it's a thing I've been looking for on my backburner for several years. It's a very interesting problem.

There are a ton of directions I can think about you taking it in.

The household application: this one is already pretty directly applicable. Have a bunch of wireless speakers and you should be able to make it sound really good from anywhere, yes? You would probably want support for static configurations, and there's a good chance each client isn't going to be able to run the full suite, but the server can probably still figure out what to send to each client based on timing data.

Relatedly, it would be nice to have a sense of "facing" for the point on the virtual grid and adjust 5.1 channels accordingly, automatically (especially left/right). [Oh, maybe this is already implicit in the grid - "up" is "forward"?]

The party application: this would be a cool trick that would take a lot more work. What if each device could locate itself in actual space automatically and figure out its sync accordingly as it moved? This might not be possible purely with software - especially with just the browser's access to sensors related to high-accuracy location based on, for example, wi-fi sources. However, it would be utterly magical to be able to install an app, join a host, and let your phone join a mob of other phones as individual speakers in everyone's pockets at a party and have positional audio "just work." The "wow" factor would be off the charts.

On a related note, it could be interesting to add a "jukebox" front-end - some way for clients to submit and negotiate tracks for the play queue.

Another idea - account for copper and optical cabling. The latency issue isn't restricted to the clocks that you can see. Adjusting audio timing for long audio cable runs matters a lot in large areas (say, a stadium or performance hall) but it can still matter in house-sized settings, too, depending on how speakers are wired. For a laptop speaker, there's no practical offset between the clock's time and the time as which sound plays, but if the audio output is connected to a cable run, it would be nice - and probably not very hard - to add some static timing offset for the physical layer associated with a particular output (or even channel). It might even be worth it to be able to calculate it for the user. (This speaker is 300 feet away from its output through X meters of copper; figure out my additional latency offset for me.)

I primarily built this for group in-person listening, and that's what the spatial audio controls are for. But what is interesting is that since it only requires the browser, it works across the internet as well. You can guarantee that you and someone else are listening to the same thing even across an ocean.

Someone brought up the idea of an internet radio, which I thought was cool. If you could see a list of all the rooms people are in and tune it to exactly what they're jamming to.

Have you seen snapcast? That's currently my go-to audio sync solution for running whole house audio. Always open to alternatives, but so far nothing beats the performance and accessibility

This looks really cool, congrats!

Just to share a couple of similar/related projects in case useful for reference:

http://strobe.audio multi-room audio in Elixir

https://www.panaudia.com multi-user spatial audio mixing in Rust

If you do RTP with pulseaudio you can know the latency of all devices and have it synced by design - no extra software needed, device agnostic. If it somehow runs linux it will "just work".

This works insanely well. What is your intended use for this? Multi room playback? Listening to music with friends?

How does it deal with the audio ring buffers on the various devices? Does it just try to start them all at the same time, or does it take into account the sample position within the buffer?

Could have used this 25 years ago when I was working in a large room with ~100 other people. Every friday an mp3 was distributed and then at the same time we all started playing it signaling that the workday has ended and the friday bar was open. Fun times.

Watch out of patent problems. There was a major dust up between Sonos and Google over audio sync technology. Disclaimer: I've worked for both companies, but not on that

Impressively accurate - Android phone in Firefox <-> Chrome on OSX == basically perfect to my ear. That's super cool, thanks for sharing!

I wonder if the technique could be adapted to work without the WebSocket server, and instead have the devices coordinate the clock offsets using peer-to-peer WebRTC connections.

It's a really intereseting vibe when you play on multiple machines. Sometimes you can notice a slight off-ness which gives this reverb effect.

This is really cool, thanks for sharing. I've got a couple of pseudo-radio stations on https://ambiph.one/ which are very roughly synchronised for all users but it's based on their device clock so it can get a couple of seconds out of sync very easily. Looking forward to picking through your code to see if there are any techniques I can borrow!

It's not open source until you pick a license. Since there is no license in this repository, it is at best source-available.

Any plans to integrate this with Apple Music or Spotify? I would assume your algorithm would work only with files uploaded to the site, but curious if you had plans to attempt something with Apple Music/Spotify

Very very cool idea, but this is a bummer: "Optimized for Chrome on macOS. Unstable for other platforms..."

Once that changes (at the very least, the macOS part), I can't wait to play with it!

have you considered using webtransport?

When I was developing Glicol (https://glicol.org/) sync, the main challenge is network jitter. Had to give it up eventually.

Furthermore, have you factored in the synchronization as perceived by the listener?

Also, it seems system-level differences, particularly in audio output latency across various OS and hardware setups, would need to be considered.

What I mean is, the variation in inherent audio output latency between different systems (e.g., Mac vs. Windows, different hardware) could easily exceed 10ms in itself.

Unfortunately the w3c webtiming community group has closed. It'd be amazing to have the browser better able to keep time in sync across devices.

https://www.w3.org/community/webtiming/

https://github.com/webtiming/timingobject

Very cool! As someone who doesn't know much about the topic, I'm surprised that "millisecond-level accuracy" is enough. I would have imagined that you need to be accurate down to some fairly small multiple of the sample rate to avoid phasing effects.

Do you have any interesting insight into that question?

Great solution based on websocket!.

My Vision: A web based VLC-type webplayer (capable of VLC level features) with support to distribute Audio channels over connect devices.

Here me out: - Mac as display(Movies screen) - iPad as a Center channel - 4 iPhones as LR and rear channels, (and something for LFE).

Is it Practical? sound cool in my head. What do you guys think??

Can this deal with latency from browser to actual output device?

(As an egregious example, AirPlay 2 has excellent audio sync but latency that is a good fraction of a second or even worse. A browser might be playing through AirPlay.)

This is the most impressive demo I've ever seen - no app download, no account sign up, no crap, just works instantly. Well done.

Works pretty good. There is noticeable desync when one device is plugged into speakers though (at least on windows). It'd be great if you had some way to get a specific device's audio lag or at least let us edit that aspect.

This is very very cool! Love it, interface, demo, no need to download anything. Impressive.

Are you already doing latency compensation? You could measure the latency, if one host will become a master and then you could compensate that by delaying the playback of the master a little bit.

Cool, keep it up!

For anyone who's curious, Airfoil (a paid app) can play simultaneously from a Mac to a variety of devices:

https://rogueamoeba.com/airfoil/mac/

Glad to see that one scene from Rainbows End/the thing I had to tell every Best Buy customer was impossible FINALLY become a reality. P3 All-Out Attack time. Kudos.

How do you handle different playback devices having small clock speed differences between them?

I did something similar with pulseaudio about 15 years ago, had an old thinkpad running Debian, and then multicast activated on my source. Worked surprisingly well!

hello! the app looks very polished and I'm sure there's a lot of usecases of this for everyone else, but for me I wanted to ask whether this can be used to sync playlist progress of your offline library (its flac ofc) across devices? its something I have not found a solution for at all, other than some Plex thingy which is paid, and if you're synchronizing for millisecond accuracy it should work for simply keeping track of the shuffle order of the playlist and last played song (I. e. the position in the ordered playlist)?

This has been popping up in various feeds of mine since yesterday (Mon 4/28)

Although I know nothing about NTP or networking really I appreciate the use of Boring Old Tech for making this awesome software

TIL what NTP is. Interesting to read about how the underlying algorithm works, and that they had pretty good accuracy 40 years ago.

Really cool but issues for me when uploading mixes (MP3's about 90 mins long, 150MB). They never make it to the playlists

Pretty cool, just the fact it works instantly in the browser with nothing to download is actually kinda wild to me tbh.

Interesting idea.

Have you thought about integrating support for timecode? Dante support also might bring your software to professional venues.

Does this resync periodically? (I mean not only when a new track starts)

The sync was so seamless I didn't even realize it was playing from my own device at first

Cool! I'd swap the 'search music' (cobalt.tools) button with the 'upload audio' button

i've been wanting to make this for so long! it's crazy that it's done completely in the browser

That's cool!

Last I heard safari was buggy and behind on web audio - did you run into any issues there?

Love it, this is impressive and very smart, no need for mic!

how does it achieve millisecond-accurate multi-device audio synchronization across browsers?

Your css is broken in that it doesn't take into account the url/menu bar on phones.

Yes it's a super annoying problem. You should change the css so that the url bar is always visible, and have a separate full screen button.

Very cool, but lacks volume controls.

Good demo!

This is very cool.

Very cool!

this looks so cool!

awesome!

Nice idea, but this project is currently written in Typescript, so I view it as a prototype at best.