DreamScape wrote: Tue Jan 06, 2026 4:33 pm
Moonee wrote: Tue Jan 06, 2026 3:56 pm
To be honest, I don't understand a single meaning of h265, h264 etc.
Videos are not a slide show of images because the file size would be too large. It's also wasteful because two adjacent frames in a video are typically very similar. So an algorithm is used by your computer to calculate the next image in the sequence instead of directly storing the entire image. h264 is older and has wider compatibility. h265 is newer, more efficient (so smaller file size), but also requires more CPU power to crunch the numbers to calculate the next image, which can cause the video to stutter on older computers.
BTW, this is why archiving a video in a win rar or 7zip file doesn't shrink the file very much at all. Modern video files are already highly compressed so archival compression doesn't add much.
A totally uncompressed video file would typically be about 35x bigger than the h264 file. Or 50x more than the h265 - and still look good on a big TV at normal viewing distance. There's dozens of ways that the video is made smaller. But the main way is breakng the picture into 8x8 pixels (for colour and luminance). Taking an average of them. Then reading the data in diagonal lines to minimise the difference, then RLE (run-length-encoding it -if the data is 0,1,1,1,1,1,1,1,0 then it can be said to be, 0,7x1,0 ). Storing the colour information at quarter the resolution of the luminance (greyscale). That's just part of the stuff for jpeg / the still image part of mp4. Then you have all the stuff about endencoding only the difference between frames before and after. And all of it with controls so you can vary the encoding quality. The technology behind it is insane. And the fact it does this complex maths for about 70million pixels a second!
Understanding the basics explains why scenes getting brighter / darker (everything is changing), lots of movement - eg water, fireworks, explosions, require massively more data than static scenes and why blurry video with less noise requires less data, also why clean stuff like CGI compresses well.
Some people think h265 does miracles, but you can only save 20-30% more than h264. I play stuff through a TV that won't handle h265 off a USB / HDD. I really love that 99% of the stuff posted here is still H264. Saves me re-encoding back to H264!
