Stopping audio feedback when sharing a video in Zoom

Working on a trial in federal court right now, and assisting with the courtroom electronic presentation. When doing the a/v setup, I learned a valuable lesson about how to prevent feedback. I had my laptop connected to speakers and monitors with a VGA cable fed through a HDMI converter to my laptop and separate audio cable - VGA will not transmit an audio signal.

I needed to confirm that I would be able to share a PowerPoint presentation in a Zoom session with a witness testifying remotely. Initially, when I tried to play a video clip in the PowerPoint I got very loud feedback - sort of like someone banging an industrial metal drum. The IT staff for the court helped me to discover a solution to the problem.

The first step was to mute both the mic and video on Zoom.

You can still play audio through the Share Screen function even if your mic for Zoom is muted.

The next step was to adjust the audio mixer for Windows so that only the feed for the 'headphones' - the port where the audio line was connected - and the sound for PowerPoint was enabled. System sounds, sound for Zoom itself, and sounds for all other applications were all muted.

. . . scroll back and forward in the Volume mixer to find other applications you may need to mute.

Finally when sharing the PowerPoint in the Zoom session be sure to click the option to share sound and optimize video.

Experiencing too much lag? Use a faster cable.

A display screen's refresh rate reflects how many times per second the image can be updated. So a display with a 240 Hz refresh rate will refresh the image 240 times per second. The higher the refresh rate the less lag you'll experience and the smoother your connection will be. You'll need the right cable to take advantage of a monitor's maximum refresh rate.

A Thunderbolt cable can support up to 40 GBs per second. USB-C only 10 gbps and HDMI 2.0 18 GBs per second, but HDMI 2.1 48 GBs per second.

HDMI cable maximum length

When setting up a courtroom for an electronic presentation, you might think that having a very long HDMI cable would work to your advantage. It could give you more flexibility about where you position your tech table from the inputs for the audio-visual system. There are certainly a lot of very long HDMI cables available of 50 feet,

100 feet . . .

. . . and longer

But with HDMI cables, longer is not necessarily better. HDMI cables may be active or passive. A passive HDMI cable will allow signals to be sent in both directions. An active HDMI cable only allows data to go in one direction, and will include a processor. An active HDMI cable will get power from the device it is connected to. At a length of more than 25 or 50 feet a passive HDMI cable will no longer transmit video and document images with maximum speed and clarity.

More sophisticated audio-visual systems may route an HDMI signal from a computer with Cat 5 or Cat 6 network cables and then pass through to an HDMI cable for a display in order to prevent significant lag over long distances.