Video Grabbing Issues

This page collects known issues and workarounds for common issues with video grabbing at various conferences. Here we try to collect different issues that we've encountered, and workarounds if we are aware of any that have helped us in the past. Please add useful URLs to the end of this article.

Hardware Issues

Symptom: VGA projector loses keeps losing contact with laptop every once in a while

Cause: Typically, VGA projectors run on a 20m+ cable. Especially when used with a passive HDMI-to-VGA adapter, the SNR in the cable degrades to a point where the projector loses sync

Workarounds: Try to replace or shorten the VGA portion of the connection. Try an active HDMI-to-VGA adapter. The connectivity of the projector should be part of your location scouting checklist.

Symptom: HDMI-connected projector shows pixel noise in an otherwise clear picture

Cause: 1) Refresh rate / interlaced vs progressive. 2) Cable running too long, 3) Badly insulated / damaged cable

Fix/Workaround: Check projector for supported resolutions. Try to add an active, mediating device (e.g. Tronsmart, Dr. HDMI) in the cable pathway to the projector, ideally midways if you suspect cabling issues.

Software Issues

macOS

Symptom: HDMI-connected projector shows black and white pixel noise

Symptom: HDMI-connected projector shows green screen for a second, then gets disconnected.

Windows

Linux

Issues to be Investigated

When do Windows and OS X enable HDCP? What ways are there to make sure there are no HDCP issues during a presentation when no video content is shown?

https://www.macworld.com/article/3042537/streaming-services/how-to-fix-hdcp-errors-with-external-monitors-in-os-x.html

https://www.macworld.com/article/3116414/macs/oops-you-cant-play-most-protected-digital-video-on-an-external-mac-monitor.html