A 4 min 1080p30fps video taken with my phone camera is 518MB, While a 12 min 1080p30fps video ripped from youtube is 341MB, both are using mp4 h.264 as codec and the youtube one isnt of lower quality, so why this big difference?
Compression. YouTube videos usually have low bitrate too.
Well yes, they have a lower bitrate, but why same quality as a bigger bitrate video? Same resolution, codec, frame rate…