Compression decreases the size of data.

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13
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2answers
5k views

How does file compression work?

So, I realised today I take file compression for granted. The ability to bundle a few files together into one, and have it come out smaller than any of them, is something I just accept as a fact, but ...
-1
votes
1answer
88 views

What 7zip settings to compress very large partition image?

I have 77 GB big partition backup image in single file and I'd like to compress it quickly. It should compress very well even on worst settings, but choosing GZIP with "Fastest" setting takes about ~1 ...
0
votes
2answers
104 views

Merging many .rar files in one .rar file

I have about 200GB of rar part files (all .rar) that I would like to merge into 1 single .rar file. I'm trying to perform this in Windows. How would one go about merging many a rar file without ...
20
votes
4answers
2k views

Can Double Zipping Cause Problems?

I have a directory that I have been storing a ton of files in. Among the 10ish types of files there are also .zips of other directories. In my personal experience I vaguely remember issues when ...
34
votes
5answers
3k views

Why is a 7zipped file larger than the raw file? [duplicate]

Possible Duplicate: Why doesn't ZIP Compression compress anything? I tried 7zipping an .exe file but it actually became larger. Is this the expected result?
19
votes
2answers
12k views

Is zip's encryption really bad? [closed]

The standard advice for many years regarding compression and encryption has been that the encryption strength of zip is bad. Is this really the case in this day and age? I read this article about ...
3
votes
0answers
43 views

Compressed file with a header containing all files within it, at the beginning of the file

I have noticed that most files resulting from a compression / archive process do not have a list of the files contained at the beginning of the resulting file, but rather at the end of it. For ...
1
vote
0answers
33 views

Store disc images on a hard drive

I'm cleaning up around my computer (A Win7 ultimate machine), and part of my plan is to rip all my program CDs and store them on a dedicated 1TB hard drive. My initial plan was to simply dump the ...
1
vote
0answers
176 views

How to unpack a compressed executable without knowing the compression algorithm

I'm not sure if this question was asked. I searched for it and could not find it. How can I unpack a compressed executable without knowing what compression algorithm was used to compress it? For ...
0
votes
1answer
2k views

Unpack NSIS executable

I am trying to decompress a NSIS executable. With the GUI version of 7zip I am able to do this and the exe is listed as: Type = Nsis Method = LZMA:25 Solid = + With the command line version 7za I ...
0
votes
0answers
35 views

Improve seeking precision for wma encoded in ffmpeg

Compressed audio formats (like compressed video) have trouble doing precise seeking. Is there something in the ffmpeg encode settings that I can change to make the resulting audio file allow more ...
3
votes
1answer
51 views

Is there any solution/utilities to compress and upload a large file simultenously?

Upload a large file via broadband connection takes time. Compress the file using max. compression ratio before upload also consume time. Is there any solution that may compress and upload file to ...
1
vote
2answers
302 views

How can I search for files that are either compressed or uncompressed in Windows Explorer?

I know that Windows explorer can colorize the NTFS compression state of a file, in both the regular and search views. How can I specifically filter/search for files that are compressed or ...
0
votes
0answers
18 views

Compress whole internet session on all apps [duplicate]

As my main internet connection, I am currently using the USB tethering feature of my Android phone. My question is this: Can I compress my whole internet session in all apps (not only in Opera using ...
1
vote
0answers
81 views

Compress 1 TB file collection into standalone archives each size no more than 2GB

I have about 1TB data stored in two drives and I need to compress and encrypt them into independent archives each size must be smaller than 2GB. Exception may be files that are larger than 2GB. Is ...
0
votes
2answers
217 views

How can I achieve the maximum zip compression? [closed]

I would like to make a "standard" zip file which contain .jpg images. Which software and switches / options should I use to achieve the maximum compression ratio? I mean maybe I can make a solid ...
1
vote
0answers
107 views

Improve slow NAS Ethernet transfer speeds: On-The-Fly Ethernet Compression with SAMBA?

Hardware: Pogoplug E02 (ARMv5te, Marvell Kirkwood 1.2GHz, 256m RAM) Software: ArchLinux, MDADM RAID 5 array, Ext4, SAMBA server This setup delivers file transfers to my Windows clients at ~21MB/s ...
1
vote
2answers
282 views

NTFS compressed folders: is it possible to tweak compression ratio?

As it seems, Windows compresses the NTFS compressed folders with the lowest compression ratio possible. While this maybe good for increasing speed and decreasing CPU load, for the files that are ...
7
votes
5answers
3k views

Whatever happened to compressed read/write filesystems?

Back in the 90s, my home computer was an Acorn Archimedes. It had on it a piece of software called ArcFS, which allowed you to create compressed archives, a bit like zip files. Unlike zip files, they ...
1
vote
2answers
324 views

Compressing multiple files into multiple archives?

I have a folder full of pdfs and I'm tired of Winraring each file separately. I don't want to put them all in one archive. Isn't there a command line I can use to make Winrar compress a file with ...
0
votes
4answers
21k views

Can I compress a RAR file again to reduce its size?

I had a 326 MB iso file that I compressed using WinRAR, with the best compression method. It got compressed to 144 MB. I want to compress more and want it to be limited to something around 22 MB. ...
2
votes
2answers
7k views

Untar a given linux tarball on MAC OS X

I have a Linux tarball that can't be unpacked. It gives me an unexpected error. I am told this is due to case insensitive on MAC OS X. How can I untar this file? tar -zxvf file.tar.gz ... x ...
-1
votes
1answer
30 views

How do I back up images with limited disk space?

I'm in a scenario where I have one 500GB hard drive and about 400GB of images I want to tar. I obviously won't have enough disk space, but I don't mind getting rid of the images as they are added to ...
0
votes
0answers
47 views

Tape backup with compression

I would like to backup a NAS to a series of LT02 tapes, (200 gigs uncompressed, 400gigs compressed.) There are about 700 gigs of data to back up. I initially tried cpio, first trying to set hardware ...
1
vote
1answer
318 views

Recursively process zip archives to extract files while discarding specific format of files

On my Windows 7 machine, I have a directory full of downloaded dumps in ZIP archives. Each archive contains few text files, PDFs and rarely XML files. I want to extract all the contents of each ZIP ...
1
vote
4answers
6k views

How do I know the gzip compression level?

Given a gzip compressed file, how do I know what compression level (1-9) was used for it?
0
votes
2answers
61 views

I cannot open folders in .tar file

I've downloaded factory image for my Nexus4 mobile, the Image folder is compressed in .tar file but it tells me that its unknown file Type: File ,, how can i open it? here take some photo of my ...
2
votes
2answers
1k views

Creating .xz with 7-Zip, claims insufficient memory (not true)

In WinXP 32bit with a Core i5 (dual core) and 4GB RAM, I'm trying to create an .xz archive from a 266MB log file using 7-Zip (GUI) on the "ultra" compression level (method: LZMA2, dictionary size: ...
0
votes
3answers
67 views

Zero sized tar.gz file found inside a tar.gz file

My current directory contains a single file like this- $ls -l -rw-r--r-- 1 root staff 8 May 28 09:10 pavan Now, I want to tar and gzip this file like $tar -cvf - * ...
0
votes
1answer
43 views

How can I compress a series of integers?

BARF2 (Better Archiver with Recursive Functionality) generates a huge barf2.count file, which is a number-only file. What's the best way to compress that?
2
votes
2answers
242 views

Compress an attachment in my mailclient inside my INBOX?

I got a lot of emails with uncompressed formats (like bmp, txt, ...) that I want to keep inside my IMAP-inbox, so I can access them from all my devices (Windows, Linux, ios, Android). Those emails ...
0
votes
0answers
282 views

Cannot complete the compressed folder extraction wizard

Recently my friend archived a folder in linux (Redhat) and uploaded in Google Drive. I have downloaded the .zip file and trying in it to unzip in windows 7. I am receiving following error: Cannot ...
0
votes
0answers
24 views

Why would my zipped file be the same size as the uncompressed files? [duplicate]

I am trying to zip 13 mp4s. The uncompressed versions of those files are 2.69GB. But when I zip them with 7zip, using Ultra compression level and any of the compression methods - including LZMA, the ...
0
votes
0answers
26 views

image drive with safecopy and compress the output

I am trying to image a drive with SafeCopy and compress the output file on the fly so that it won't take up way too much space. (aka 500GB > 50GB) Will this command work? sudo safecopy --stage1 ...
0
votes
1answer
48 views

Should I extract before running?

Is it not wise to run an executable from a zipped file without extracting first? Someone explained to me that there is no need to extract first. He explained that zipped files are nothing more than ...
0
votes
1answer
608 views

How to compress 14 GB of csv files with 7zip (minimizing space)?

I have to compress 14 GB of csv files with 7zip. What options should I use to achieve the highest compression? I have tried Ultra Level with both LZMA and PPMd compression method, obtaining results ...
0
votes
0answers
50 views

Fast way to forward an Outlook email as a zip

I need to find a quick way to select an email in Outlook 2010 and forward the email as a zip attachment. The recipient will always be the same. The subject and body of the email will always be the ...
1
vote
0answers
448 views

Difference between downscaling 1080p to 720p in real time and downscaling during encoding?

Suppose a high quality, uncompressed video is re-encoded twice, with almost identical encoding settings at a relatively low bitrate of 4mbps, but at different resolutions, first at 1080p, and then at ...
1
vote
0answers
44 views

Webm video flashes compression artefacts

Doing som testing on capturing video from VirtualBox for a screencasting project. VirtualBox uses webm for video and it works sort of OK. However, it has "flashes" of heavy compression artefacts. ...
-1
votes
2answers
85 views

Do web browsers download faster than your max bandwidth?

Since content is compressed on transmission and uncompressed on the browser, does that make the transfer rate faster than your bandwidth? Or is there another term for this? For example, a 1GB white ...
2
votes
5answers
2k views

Compression software with slow rates, and very high compression

I have a lot of data that I don't have to 'get at right away', and I was wondering if there was any compression software I could use that could compress it down to a smaller size than I'm currently ...
5
votes
1answer
356 views

Change Excel Zip Compression Level in Windows

Excel compresses its files using Zip-Deflate and stores it. However, the compression level is far from the best. To reduce the size and send it across I have to unzip and re-zip it manually everytime. ...
0
votes
0answers
48 views

Sequential Compression of [Text] Files (7zip and Windows)

This is with Windows 7. I have an iterative process, and on each iteration it produces a text file. What I want to do is compress this text file on each iteration to an archive. I'm using vb.net and ...
7
votes
2answers
4k views

Multithreaded support in 7za

(I posted this first on serverfault, but then I realized it probably belongs here.) I'm trying compress a very large text file using 7za (p7zip) 9.20. The -mmt option doesn't seem to have any effect. ...
2
votes
2answers
172 views

Compressing compressed .tar.gz files deterministically

I want to perform a series of recompressions of compressed files to study their properties. At first, I tried simply recompressing .zip files in a loop: for f in $(seq 1 100) do zip $f.zip -9 -v ...
0
votes
1answer
24 views

Below what network speed should I be using compression for an rsync transfer?

I'm transferring some files from a remote server. The speeds for the transfer are abysmal (~1 MBps), and have got me thinking about optimizing the transfer for speed. At what network speed does it ...
10
votes
4answers
37k views

What are the best options to use when compressing files using 7 Zip?

I often have to gather log files and upload them to a central server (Owned by another company). The central server has a size limit of the file, so I am trying to create the smallest file possible ...
1
vote
0answers
233 views

Need to read a Windows 98 DRVSPACE.000 file in Windows 7

Today I came across a DRVSPACE.000 file in my archives and I want to recovers its contents. Beside the file is a READTHIS.TXT which reads: This disk was compressed using DriveSpace 3, which ...
0
votes
1answer
853 views

Does anyone know an effective method to ultra-compress files?

Does anyone know an effective method to ultra-compress files? You might have seen some PC games compressed to incredibly small sizes here and there (like GTA San Andreas which was compressed to 1mb ...
2
votes
0answers
622 views

tar: Cannot create symlink : File exists

I backup lots of gigebytes files in to myproject.tar.gz, and compress success without errors. Now, I want to decompress all to an folder "myprojects". adan@adan-Latitude-D630:~$ tar zxf ...