[Bug]: Key transpose over web app client is not supported

[dsillman2000]

Before reporting

• I'm on the latest release and the issue still happens.
• I searched existing issues and didn't find a duplicate.

What happened?

When hosting StemDeck over network, clients are not able to transpose audio +- semitones.

On the host machine, the transpose feature works exactly as advertised. Clients which try to use the global key transpose see greyed out "+" / "-" controls. Clients which hover over the "K" transpose track button see a tooltip which says "Transpose needs Web Audio."

Steps to reproduce

1. Open Stem Deck and host over network.
2. Connect to Stem Deck server from a client machine.
3. Upload any audio / select any audio from Youtube.
4. After processing completes, try to use the global key semitone controls or hover over the "K" button on non-drummer tracks.

Operating system

macOS (Apple Silicon)

StemDeck version

v0.16.1

How did you install it?

macOS DMG

Logs / screenshots

This issue appears both with the "install-with-DMG-then-host" workflow as well as the "clone-build-then-host" workflow from the README.

[thcp]

Thanks for the detailed report, and for spelling out both workflows. That saved me a lot of guessing.

You found a real problem, though the cause is not quite the one the app claimed. The pitch stage is built on AudioWorklet, and browsers only hand that API to a secure context. https:// and localhost count. A plain http://192.168.x.x does not, so a client opening StemDeck over the network is never given the API at all and the pitch stage cannot be built. That is why it works on the host and nowhere else.

I measured it rather than assuming, serving one page three ways:

http://127.0.0.1:8777/     secureContext=true   audioWorklet=true
http://localhost:8777/     secureContext=true   audioWorklet=true
http://192.168.1.14:8777/  secureContext=false  audioWorklet=false

So the greying out is correct. What was wrong is everything the app said about it, and that part I have fixed:

• The lane tooltip said "Transpose needs Web Audio". Web Audio was working fine. It now says transpose is not available over a network connection, which is the truth.
• The global key control said nothing at all. Three dead buttons still offering to transpose up a semitone. It explains itself now.
• Speed was the one nobody noticed. Without the pitch stage the audio is resampled instead, so changing speed also changes the key, and the control gave no sign of it. It says so now.

What I have not fixed is the capability. Transpose still will not work for a network client, because no change inside the page can grant an API the browser withholds.

There are ways around it if you need transpose from another machine today. The simplest is to make the client's origin localhost with an ssh tunnel: ssh -N -L 8000:localhost:8000 user@host, then open http://localhost:8000 on the client. tailscale serve also works and gives you real HTTPS with no certificate warnings. Both are in the README troubleshooting section now. I deliberately kept them out of the tooltip, because answering a musician with port forwarding is not much of an answer.

There is a real fix available and I have opened #558 for it. createScriptProcessor is not secure-context gated, so a fallback path could make transpose work over a plain LAN IP with no certificate at all. It is a bigger piece of work than it sounds, since it runs on the main thread and would have to take over tempo as well as pitch, so I want to prototype it before promising anything. The measurements are all in that issue.

Let me know if the tunnel gets you going in the meantime.

Disclaimer: This answer was generated with help of AI because main dev is juggling hard between other tasks.