[bavell]

Interesting! Thanks for running mediainfo on them to compare.

When encoding videos there's a "speed" parameter that basically tells the encoder to spend more CPU time compressing the frames. It results in a smaller output size while maintaining the same level of quality but takes much longer to encode. I'm sure that's part of what YT is doing here, an initial quick encode to get the video live then another pass to reduce filesize for long term storage. Good find!

I'm guessing that the perceived higher quality in the smaller file is because the encoder was able to find a more accurate way to represent those frames with the same or fewer number of bits since it has more time to search for the optimal encoding.