No, movies and music files are already compressed, so compressing them further won't gain anything. In fact it will actually increase the file size because compressed files require some overhead. So even winrar won't help, though it might be convenient to have one big file with everything in it (you can even break it up into multiple part files.)
this post was submitted on 16 Mar 2025
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TV shows and movies are already compressed. If you try to compress something that's already compressed, it typically ends up bigger if anything.
Have you tried compressing it again?
Why does it get bigger? I've wondered that for a while now.
I would think that compressing something that's already compressed would still compress it further but at diminishing returns.
Once the files are added to the zip folder your also adding information about the files so they can be removed.
Ohhh you know that makes sense. So, basically, what you're saying is this?
[Files] = [Files]
[Compressed Archive] = [Files] + [Archive Metadata]
If you can sacrifice quality, you can encode the videos at a lower bitrate, but that is lossy compression, not lossless. Also, if your videos are in h.264 codec, then transcoding them to h.265 and preserving the quality may be a way to get the files smaller. You would use a tool meant for video, like Handbrake for this, and not winrar or other generic compression tool.
As most have said, doubling up compression won't usually get you much.
However, video compression is usually designed to facilitate performance of sequential reads because videos are typically played beginning to end, so theoretically there may be ways to compress them more if you're willing to make sacrifices there.
I doubt RAR is the way to do it, though. It just hasn't been designed for this kind of data.
Maybe there's a video compression format out there designed specifically for archival storage, but I'm not aware of it.
ISO won't get you any further compression, that's for sure.
You could certainly test this out yourself and let us know if you get any space savings.
If I use winrar to compress 80gb of tv and movies.
You haven't gained anything by doing so since video is already compressed. Compressing data that is already compressed will usually make it slightly larger - or if you're lucky maybe you'll save like 1 megabyte space, not really anything worth the trouble.
Then can I compress it further by making it an iso?
ISO is not compression.
Iso is a container format; it’s a 1:1 mapping to how the bits are stored on disk with a header at the start describing the structure. Bin/cue separates the header into a separate file and can include data structured in ways that don’t comply with the ISO-9660 standard.
WinRAR is a compression/decompression program. It supports multiple archive types and compression formats.
Depending on the type of data you are compressing and whether you want lossless or lossy compression, you’ll want to select a different compression algorithm.
Depending on how you plan to use the files, you’ll want to use a different archive format.
Assuming you use the rar archive format, you still have a lot of options to consider. Should the data be encrypted or not? Should the directory structure be encrypted or not? Do you want parity files and segmented archives, so that if one of the parts gets corrupted (or goes missing), you can still extract the original data in a lossless way?
Beyond all that and selecting the compression algorithm that best compresses the type of structured data you’re storing, the general rule is that if you’ve got lots of data, using the largest dictionary and the largest compression window you can will result in the best compression.
So the dictionary is essentially a code book that says “when I see data x, represent it with data y in the file”. The compression window is how much of your original data is loaded into memory at any given time for the dictionary to look at and compress.
[edit] if you’ve got video, the best compression format commonly available today is H.265. This is a lossy compression format, meaning you’ll never be able to precisely recreate the original file. But it’s close enough not to matter at the right compression settings.
And if you’re using H.265, the best container format to stick it in is an MPEG-4 archive (typically with a .mp4 extension).
The result is a highly compressed and structured file. Loading chunks into memory for rar compression will usually result in a larger file, because the data is already compressed in a structured manner that a general compression algorithm can’t match… meaning that you’d get the input of xxxxx resulting in output of yyyyyy.
Well, it's sort of possible to compress large things into small sizes. But I don't think it would work for this situation.
There are things called ".zip bombs". Where an otherwise small file, when unpacked, can take up a large amount of space.
A famous example of a zip bomb is titled 42.zip, which is a zip file of unknown authorship consisting of 42 kilobytes of compressed data, containing five layers of nested zip files in sets of 16, each bottom-layer archive containing a 4.3-gigabyte file for a total of 4.5 petabytes of uncompressed data.
Zip bombs wouldn't apply here, from what I understand to create those you'd have to start with uncompressed data. The typical example is using a bunch of zeroes as the starting point, not only is that compressible but the compression algorithm will look for redundancies in the data to increase the compression efficiency (a bunch of zeroes would have tons of redundancy).
Stackoverflow has a good discussion on it https://stackoverflow.com/questions/1459673/how-does-one-make-a-zip-bomb
Just buy another hard drive, damn.
To get the maximum compression out of video you should use a video codec like av1 or hevc. WinRAR wont compress video well at all and making it an ISO is also pointless.
I would suggest checking out handbrake for a good user friendly video compression tool.
For lossless compression, things other then video/audio, you should movr to 7zip over winRAR.
Bottom line, winrar isn't the tool to compress video files. In short it's more complex, but zipping, raring etc... those methods are all the ideal way to compress executables, word documents etc... In short, most likely your video files are already compressed as much as they can be without loss of quality. However if you were to attempt to make them smaller, most likely you'd use something like handbrake or some other video codec converter to actually try to shrink them.
The short answer is no.
You can do an easy experiment to see this using image files. Grab a random JPG file and open it in a graphics program and save it as a BMP format image.
JPG is already compressed, and BMP is absolutely not compressed. Then try compressing each image. You’ll find that the JPG doesn’t get much smaller, or might even be a bit bigger when compressed. Now do the same with the BMP - that one makes for a smaller RAR!
The main issue here is that compression is about removing empty space in a file (it’s a weak analogy but bear with me). If the file itself already had some kind of compression (basically every AVI or MP4 or MKV you download probably is already compressed), then there’s already a lot less empty space inside the file. RAR doesn’t have much empty space left to work with, so it can’t really reduce the file size any more.
It’s worth doing some testing on a single movie to see how this all works. You’ll probably find that it’s best to just leave the files exactly the way they are. No RAR. No ISO. No tricks. The gains simply aren’t there.
If you’re looking to save on some disk space with your movies, you’d get a lot farther by just deleting one movie you don’t really want that badly. The amount of space you get back from that will exceed your compression gains. It also means you don’t have to go and uncompressed the movies every time you want to watch one.
Put the data inside a mini-blackhole and activate Future Gadget #8 PhoneWave (name subject to change)