Desktop Window Image Degradation

This is a desktop window composed through ManyCam and viewed as a participant in Zoom.


This is the same window shared directly by zoom.

I emphasize that both screengrabs are from the participant’s computer - i.e. apples to apples with respect to network performance etc.

The top image isn’t really usable, especially since I’d ideally like to shrink the font size in the editor.

This might be the same issue as: Degraded powerpoint quality when using Manycam

This image degradation is an instadeath with respect to using ManyCam for what I intended it for - instruction. May I submit that this degradation be the first thing to be remedied in the next release? Please?

In fairness, I am making a supposition that Zoom is sharing windows as images. It would be their advantage if they shared windows via a dedicated encoding scheme or perhaps motion jpg or other scheme better suited to screenshares. Manycam wouldn’t have access to this encoding.

Hi @Perry_Kivolowitz,

The reason of low quality is downscaling. Zoom takes from ManyCam the resotion that it wants and that resolution is low, tupically 720p or even less if you don’t check HD in Zoom (you can check what Zoom takes by right-clicking on big blue button). No matter what resolution is taken in ManyCam, if Zoom asks ManyCam to provide 720p it should do it by downscaling your video feed to 720p. ManyCam can’t force Zoom to take real resolution as Zoom suppose that web-cam provides human video, not windows. Even though ManyCam uses box sampling for scaling there is no solution to scale 4K to 720p and keep everything crisp (FIXME). The only solution is capturing 1:1 what Zoom takes, e.g. capture 720p of desktop area in ManyCam. I think that Zoom captures and transfers desktop differently that web-camera, but again we can’t force Zoom to do anything.
Good news is that we are working on video overlay feature that will render your web-cam feed over entire screen (with removed background), so zoom can capture you over the entire screen.

I submit the easiest to implement first pass at improvement would be to replace the box scaling with something more sophisticated. I say this is easiest because I assume your scaler is encapsulated in a function so that changing it in one place will change it for all places.

Zoom’s perfect knowledge of what it is doing gives it the advantage as we both pointed out. I’ll go so far as to guess that when zoom is sharing a window, they’re using a VNC-style encoding.

Here’s an idea that requires NO changes on your part (the best kind). Would you consider creating a FAQ article detailing how to tune desktop screen resolution / ManyCam settings to Zoom settings so as to reduce scaling (at the highest resolution possible)?

Open the Zoom settings and go to the tab called “statistics”. There you can see how much downscaling is done for your video signal and for your screen sharing signal.

Once you did that, keep that settings window open.

Now choose your normal webcam (not Manycam) as your video camera in Zoom. Then share your Manycam in Zoom as a screen share, using Zoom’s menu called “share / advanced / content from second camera / Manycam”.

Now the image of your webcam should be broadcast in downscaled quality but your Manycam signal should be broadcast much better than that.

What do you see in the statistics page of Zoom that you left open? Is your shared screen signal downscaled or not?

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Hello @mattes3 - I’m having the same issue as @Perry_Kivolowitz - I followed your advice from 9 Sep and noted that Send resolution is 640x360 and Receive resolution is half of that (320x180) - see attached - when I select ManyCam as my camera in Zoom - which is clearly extremely poor. At all times, clicking the big blue button on ManyCam, I can see that the send resolution is 1280x720 per my settings.

Q: What is causing Zoom to downgrade this by half when I use ManyCam?

Yet, when I Share Screen in Zoom, the resolution is a very pleasing 1920 x 1080 for both me and my meeting participants.

FYI, I note that when I use my desktop HD camera only, the Zoom Statistics still show 640x 360. and yet HD is enabled in the settings.

What to do?