How do I publish an output with a larger screen size?

I publish PowerPoint presentations and capture them on my screen using Camtasia in order produce them as MP4 videos.  The current screen size of the web presentation does not allow me to capture the web video in Camtasia at a size that would allow me to convert my web video into a high-definition MP4 video.  Currently, my presentations are posted on blackboard and stream at a quality 360p but I would like the video to stream at 720p or above.

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