First you just need to insert your background image or video and add a green screen video footage you shot, or you can just insert one copyright free footage from YouTube (just make sure you have the rights to use that footage). To learn how to insert video on your PowerPoint, watch this tutorial
Then edit the Alt Text of the green screen footage and insert %%GREENSCREEN% text in it. If you want to mute the Youtube video, add %%MUTE% in the Alt text.
If your footage is using Blue screen instead of Green Screen, change the text to %%BLUESCREEN%
Now the sky's the limit ! You already have the tool to create professional looking videos !
Update : For youtube videos, the start settings is no longer supported by PowerPoint. Instead, you can use the Alt text to indicate when to start or end the green screen sequence. Use the timing in seconds of the video you want to insert.
For example to start the video at the 15 seconds mark, add the following command (with a space) after the %%GREENSCREEN% text:
This supports decimal seconds, to start at 5.7 seconds add the following text:
To end the video before the end of the Youtube video, you can also use the Alt text. To end the video at the 52 seconds mark, simply add:
IF you want to end the video 10 seconds before the end of the video, use the following syntax:
If you want to mute the Youtube green screen videos, insert the following text: