After reading the link you provided I noticed that we can also provide an mjpeg.

Depending on what your test requirements - this may be sufficient for you. As a terminal command with ffmpeg installed:

ffmpeg -i oldfile.mp4 newfile.mjpeg

then I tested by running Google Chrome from the terminal using:

google-chrome --use-fake-device-for-media-stream --use-file-for-fake-video-capture=newfile.mjpeg

After navigating to Tracking JS I could see the video being played back.

I hope that works for you!

If someone ever needs to mock a video dynamically, this is what I've used (forked from here)

await page.evaluate(() => {        const video = document.createElement("video");        video.setAttribute('id', 'video-mock');        video.setAttribute("src", 'https://woolyss.com/f/spring-vp9-vorbis.webm');        video.setAttribute("crossorigin", "anonymous");        video.setAttribute("controls", "");        video.oncanplay = () => {            const stream = video.captureStream();            navigator.mediaDevices.getUserMedia = () => Promise.resolve(stream);        };        document.querySelector("body").appendChild(video);    });

• the key is to return Promise.resolve(stream)
• oncanplay is better than onplay because it is triggered after the video is playable

This flags are still necessary:

'--use-fake-ui-for-media-stream','--use-fake-device-for-media-stream',

In the end, with this script different camera mocks are possible for every page - especially useful when using browserless!

Mocked/Fake Raw Video (2021)

Use y4m if you want raw frames without Chrome having to run a decoder:

ffmpeg -i original.avi -pix_fmt yuv420p video-for-chrome.y4m

Then, start Chrome:

chrome.exe --user-fake-device-for-media-stream --use-file-for-fake-video-capture=video-for-chrome.y4m

Note: There is no longer any reason to have to modify your y4m file's header. Chrome has since been fixed.

This method uses less CPU, but will take up a good deal of hard drive space for the raw video. Keep your video file short. Chrome will loop it.