@beardalaxy Have you met our lord and savior ffmpeg? Codec choice and bitrate are the most important aspects to consider when encoding audio or video. Newer codecs (such as AV1, H265, VP9, etc. for video) generally have better performance in quality per bit but have smaller hardware decoder support which could make the video choppy or unplayable on low performance devices. When targeting specific file sizes, it’s best to encode with a target bitrate using two-pass encoding instead of a target quality.

There’s also the question of quality vs size. You can encode a feature length movie into 16 megabytes, but it’s debatable if a movie of that quality would even be enjoyable to watch.

This calculator is useful for getting ballpark numbers on what bitrate to choose for video/audio files of a specific length to get a specific file size. If you’re working with a hard limit you might have to play around with them and other settings (framerate, resolution, audio channels, etc.) to squeeze the most out of it.

The attached file is encoded in VP9 and Opus in a webm container. It was encoded with a target of 16mb and overshot it by 0.2mb, and the frame rate had to be sacrificed, dropping down to 10 fps from 23.98. The total bitrate came out to be 27 kb/s (I think the audio was targeting 7 kb/s, so the video is around 18 kb/s), much less than the 1181 kb/s (972 + 195 kb/s) of the mpeg4 and mp3 avi original.