TLDR: Curtail losslessly compresses photos without losing date/time metadata. What program like Curtail can do the same with video’s (preferably with MKV support)?
Curtail is FOSS Software for Linux that I’ve found extremely helpful. It’s designed to bulk losslessly compress your images and photos without losing the date & time metadata in them. I’ve found this really helpful for skimming down the overall storage-use of my photo’s.
But the thing that takes the most space on my PC is video’s. You see, I record all of my videogame gameplay and store them on a hard drive. This takes many hundreds of gigabytes of space and is ever-increasing; and compressing them without losing any quality while retaining the date & time metadata is invaluable to me.
I’d love a program that functionally acts the same as curtail, but losslessly compresses each individual frame of a video rather than a photo. Curtail doesn’t provide this, so does anybody know of any programs I can use that do this? MKV support is preferable, as that is how I store my video’s, but still tell me about it even if it doesn’t support MKV.
“Lossless” has a specific meaning, that you haven’t lost any data, perceptible or not. The original can be recreated down to the exact 1s and 0s. “Lossy” compression generally means “data is lost but it’s worth it and still does the job” which is what it sounds like you’re looking for.
With images, sometimes if technology has advanced, you can find ways to apply even more compression without any more data loss, but that’s less common in video. People can choose to keep raw photos with all the information that the sensor got when the photo was taken, but a “raw” uncompressed video would be preposterously huge, so video codecs have to throw out a lot more data than photo formats do. It’s fine because videos keep moving, you don’t stare at a single frame for more than a fraction of a second anyway. But that doesn’t leave much room for improvement without throwing out even more, and going from one lossy algorithm to another has the downside of the new algorithm not knowing what’s “good” visual data from the original and what’s just compression noise from the first lossy algorithm, so it will attempt to preserve junk while also adding its own. You can always give it a try and see what happens, of course, but there are limits before it starts looking glitchy and bad.
I know that lossy normally lessens the image quality in the compression process, but Curtail has two options:
Lossless mode: Compresses the file by removing unnecesary data that does not affect image quality; thus reducing file size. Lossy mode: Compresses the file much further by lowering the visual quality of the image; thus reducing the file size but looking a bit worse.
After using the lossless mode, I’ve personally done very thorough image comparisons to see if there was any discernible difference between the original file and the compressed file. I could not find any visual difference.
In Curtails own words on their site “It supports both lossless and lossy compression modes with an option to whether keep or not metadata of images.”
Curtail is a wrapper around tools like pngquant, jpgoptim and oxipng. In lossless mode it optimizes and reorders e.g the compression tables. I know of no tool that does that for video data and I am not even sure that is feasable. Video is not stored as a simple sequence of images.