Proxy file bigger than source video!

[Durga_swaroop_Perla]

Hi, I have a 1080p, 60 FPS screen recording of about 10 mins with a file size of 50 MB.

Shotcut had a problem playing it in real time and so I created a proxy for it.
But the proxy file, 360p one, came to be 500 MB. That’s just insane. Isn’t proxy supposed to be a smaller file for keeping the access fast?

How will it work in this case?

[Austin]

@Durga_swaroop_Perla

Isn’t proxy supposed to be a smaller file for keeping the access fast?

No.

Access is slow on the original file because compression is heavy and it takes lots of CPU to unpack it.

Access will be fast on the proxy file because the compression was unpacked in advance with the trade-off being a larger file on disk. Your hard drive should have no problem keeping up with the needed data rate, so it’s a good trade-off to keep CPU usage lower.

This is pretty much the same logic as your other question:

Edit Friendly clips are too big

Adding to what @DRM said, the size increases because the source file uses IPB compression. That means one frame is fully described, and then the next 120 or so frames are described as differences from the base rather than being independently described. Since differences are usually minor, this saves a lot of space. So, to view frame 40, the base frame would have to be read and then the 39 differences after it applied to reconstruct frame 40. That’s why editing IPB video is slow. The conversion …

[Durga_swaroop_Perla]

Then how are proxy files different than Edit friendly files?

[Austin]

Good question. The high edit-speed goal and the methods to get that speed are the same. The difference is the quality target.

Edit-Friendly tries to be as true to the original as possible. It is a permanent substitute for the original file. It will have the same resolution as the original.

Proxy is much lower in resolution so there is less data to process during editing. It doesn’t even joke about looking as good as the original. It also uses a lossy codec that throws away much more color information than the edit-friendly versions as an additional way of saving disk space.

Edit-Friendly is used for the final export. Proxy is not. Hence, they have different quality targets for different jobs.

[Durga_swaroop_Perla]

Thank you. It’s clear now.