搜尋 Mozilla 技術支援網站

防止技術支援詐騙。我們絕對不會要求您撥打電話或發送簡訊,或是提供個人資訊。請用「回報濫用」功能回報可疑的行為。

Learn More

How to select camera?

  • 3 回覆
  • 2 有這個問題
  • 46 次檢視
  • 最近回覆由 UniQMG

more options

On Firefox 90 on Ubuntu 20.04, when a site asks for camera and microphone permissions, it’s not possible to select any device anymore. It just shows the default camera and the default microphone.

Earlier Firefox releases used to show a selection list for the camera and also another one for the microphone.

My default camera is the one built into the laptop and I would like to use an external one that has adequate picture quality.

Can you please help selecting a camera with the new Firefox?

所有回覆 (3)

more options

What site or app are you trying to use the camera for? Can you do it in Chrome?

由 jonzn4SUSE 於 修改

more options

You are right, it doesn’t have the same behaviour on all sites. It doesn’t work on Nextcloud Talk.

Is it something that the website controls or is it a setting in my browser that is specific to a site?

more options

I was having the same issue and looked into it. A website using the `getUserMedia` API can force a specific device to be requested, which removes the ability to select a device from the permission prompt.

For example:

   // Forces the permission prompt for a specific device
   var id = (await navigator.mediaDevices.enumerateDevices())[0].deviceId;
   await navigator.mediaDevices.getUserMedia({ video: { deviceId: { exact: id } } });
   // Allows you to pick a specific device
   await navigator.mediaDevices.getUserMedia({ video: true });

I wrote up a userscript that defeats this. You can load it with any userscript manager (such as tampermonkey). May also run into issues with CSPs on some sites, copy-and-pasting it into devtools also works.

 // ==UserScript==
 // @name         Force allow camera choice
 // @version      1.0
 // @author       UniQMG
 // @match        *://*/*
 // @run-at      document-start
 // @grant       unsafeWindow
 // ==/UserScript==
 (() => {
     let original = window.navigator.mediaDevices.getUserMedia;
     original = original.bind(window.navigator.mediaDevices);
     window.navigator.mediaDevices.getUserMedia = (constraints) => {
         for (let devtype of Object.values(constraints))
             for (let key of Object.keys(devtype))
                 if (devtype[key].exact)
                     devtype[key] = devtype[key].exact;
         console.log("Fixed device request", constraints);
         original(constraints);
     }
 })();