7-zip tricks?

Does anyone have any tips on how to get the best file compression with 7-zip? I have a lot of backed up media on external drives that I want to archive so I can fit more in, but I'm having no luck whatsoever with 7-zip. Even using Ultra compression, I inevitably end up with archives that are either A) the same size or B) even bigger. I've tried single part and multi part archives. I'm just not getting it =/

 

Any chance you're trying to compress lossless audio and wav's?

 

No, mostly just avi and mkv files.

 

use winrar much better compression

 

I don't have any tips (sorry) but it's quite common that compressing BLOB type files (MP3, Video, Executables) end up either not compressing much at all or actually creating larger files due to the overhead involved with adding the zip info file overhead. The best type of files to compress are txt files or other types of raw dat files such as database dumps that involve english language ASCII characters. Large XML files and large database dumps compress particularly well.

Video and image data is already dense and massively compressed (using MPEG encoding etc.), the only way to reduce size is by encoding it at a lower frame rate and accepting lower quality, which takes work to go through each file and do.

You can read more here:

http://en.wikipedia.org/wiki/Data_compression

If anyone comes up with a way to compress video more effectively, you can run to the U.S. Patent Office and immediately claim a patent and probably buy your retirement home right after that as every software company will be running to you offering you millions of dollars for the patent

 

WinRAR FTW d00d

 

Here's the trick to get up to 60% compression on almost any type of file.

1) get magic iso and compress your data as dvd images with uif compression (chooose high compression setting). That's about 50% compression. The best part about this is that you can have on-the-fly decompression which means you don't have to decompress before you can use the data.
2) Then use 7zip to compress the dvd image with LZMA or UPX with 16-32M dictionary size in solid archive format. Winrar with 4096K dictionary size with solid archieve works just as well, but much faster.
3) Repeat step 1 and 2 to get more compression.

 

what you suggest is against all laws of compression

lossy compressed movie and audio data normally can't really get compressed much. that's just the way it is. if you follow the rule of jackluo you reach at one point 1 bit. and 1 bit can't represent your movie/music data

 

Bingo! Assuming your files are already using lossy compression, there's nothing you can do with lossless compression (such as 7-Zip) that will shrink it further.

You could transcode the compressed files to a lower-bitrate lossy compression, but you will suffer further (and irreversible) quality loss in the process.

 

1) This thread is about 7zip.

2) This thread is about file compression, not $29 in wallet compression.

3) Media files are usually very compressed already, so it's not likely to get good compression out of zipping/rarring/whatevering them anyway. Even if WinRAR could compress a particular file "better", to get more than a fraction of 1% would be asking a lot.

 

It's impossible to reach 1bit with my method. There's an overhead to my method. My guess the minimum file size is less 1% of the original file.

Compressed movies, audio, zip, rar, 7z, uif all compress file differently, but they also have similarilties.

Movie compression use "repeated" pixles on each keyframe to "reconstruct" the movie and of course with other more advanced techniques. Thus you're able to get more than 99% compression ratio is some circumstances.

Advanced and modern audio codec are pretty efficient. E.g. WMA 10 Professional codec can compress audio file by at least 90% and still maintain the quality*. Average people won't notice the difference between PCM audio stream and a properly compressed WMA 10 Professional. Other competing codecs are AAC-HC (forgot the spelling). Other losses codec such as FLAC, MP3 lossless, WMA 9.2 lossless, AAC lossless can achieve about 50-80% compression ratio without losing any quality.

Zip, Rar, 7z all make use of "dictionaries". Dictionaries are basically a lookup table of some number values. Eg 001 = 00000000000011111111111, 010 = 01010101010101010....etc. They typically achieve about 10-90% compression ratio depending on what you're compressing. E.g. a notepad text file will probably result in a 90% compression ratio using 7z UPX or LZMA compression method while a h.264 movie will probably get 1% compression ratio.

UIF and other types of disk image compression uses a different type of "dictionary" type of compression. Instead of compressing the files, magic turns those files into a disk image (typically known as .iso file) then compress the .iso file itself. .ISO file represent each bit (0s and 1s) on a disk (cd/dvd/bd/hdvd...etc). UIF file is optimized to compress disk image thus it usually achieve about 40-60% compression ratio.

With a combination of different type of compression method, you'll be able to shrink a very large file into a small one (usually above 50% compression ratio).

Of course, there are many other types of compression methods, and their result may vary.

The most common one that most people will use, but never realize that hey're using is NTFS compression. You get anywhere from 1% to as much as 80% compression ratio.

Here's one more "less obvious" and "almost nobody knows about" compression method.
Say if all of your files are 4Kbit in size and your HDD cluster size is the default 4Mbit, you can compress your file by over 1000% (i think i did my math right) by formatting your hdd with 4Kbit cluster.

Of coruse, the above are all lossless compression method. There are also tonnes of lossess methods.

E.g. you can delete all the " data" or "journaling" on ntfs file. E.g. last access dates, ussage rights...etc.