iMovie: extremely large file size for static picture with sound
I have an m4a file that is 93.5 MB large, and a PNG image file that is 98 KB large. I want to make a video that is the length of the m4a file, with the image shown statically. That is all fine, but exporting yields about 1 GB for quality "High". I don't whether quality refers to sound, video, or both, but I do know that I want the quality to be that of the m4a and PNG file.
How do I get a resonable export file size? It doesn't make sense the export file is 10 times the original data. It cannot increase the quality, and it doesn't make sense if the export format duplicates the data 10 times.
How do I get a resonable file size, apart from changing the settings in the export dialog?
MacBook, macOS 11.4