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javascriptc++webrtc

How is the value of MediaDeviceInfo.deviceId calculated in Webrtc?

I am wondering how is the value of MediaDeviceInfo.deviceId calculated in Webrtc?

MediaDeviceInfo.deviceId is a property used in web APIs of Webrtc.

I have found a document MediaDeviceInfo, but still cannot get the answer. Is it directly from the uuid of the connected Media Devices?

I guess there may be some calculations in native codes, but I am not familiar with its native codes.

Solution

  • You can find the Chrome implementation here: https://source.chromium.org/chromium/chromium/src/+/main:content/browser/renderer_host/media/media_stream_manager.cc;l=1653;drc=917850e016efe08e27c61eaa03e6fc27200e5be1

    It is a hmac of the device id with a per-origin salt that has the same lifetime as cookies (for privacy reasons). This hides any device uuid.