Windows 7 Forums

Welcome to Windows 7 Forums. Our forum is dedicated to helping you find support and solutions for any problems regarding your Windows 7 PC be it Dell, HP, Acer, Asus or a custom build. We also provide an extensive Windows 7 tutorial section that covers a wide range of tips and tricks.


Windows 7: Check Compression Level In An Existing .rar File?

31 Oct 2014   #1
Comicsnut

Win 7 Home Premium x64
 
 
Check Compression Level In An Existing .rar File?

Hi all,

Just wondering if there's a way to check the compression of an already rared .rar file.

I'm trying to create a profile within WinRar and want to ensure it's doing exactly what I want it to do as far as compression (Store as opposed to the other compression levels). I don't want the files stored to be compressed in any way.

So, like I said, I know how to create a .rar without any compression, but I want to check that the files were stored after the .rar is made.

Thanks!


My System SpecsSystem Spec
.
01 Nov 2014   #2
Alejandro85

Windows 7 Ultimate x64
 
 

As far as I know the compression level is not stored anywhere within the file. If you ask WinRar for file information it will only report sizes and compression percentage. The only relevant info is the dictionary size, but the level "stored", "fast", "best", etc don't seems to be saves anywhere, so I think it's not possible to query it in an already created file.

However, if you just want to check if the rar is really uncompressed at all, it's possible to look at the compression level and the file sizes. If compression is at 100% and the total file size is equal to the compressed file sizes it means that the file was in fact "stored". For all other levels you can only guess, but the "no-compress" level is noticeable.
My System SpecsSystem Spec
01 Nov 2014   #3
Berton

Windows 7 Ultimate 64-bit, Windows 8.1 64-bit, Mac OS X 10.10, Linux Mint 17, Windows 10 Pro TP
 
 

And do note that some file types don't compress much or not at all, see it with images, text files can compress quite a bit. Different programs tout they do better than others. The thing the no-compression would be good for is avoiding blocking of the actual file extension on the Internet.
My System SpecsSystem Spec
.

01 Nov 2014   #4
Comicsnut

Win 7 Home Premium x64
 
 

I use no compression to store images. I was under the impression that once the file is compressed it "tosses" out bits of data...like a lossy .mp3 compared to a .flac.

And I figured once that compression is done the file is changed permanently.
My System SpecsSystem Spec
01 Nov 2014   #5
Berton

Windows 7 Ultimate 64-bit, Windows 8.1 64-bit, Mac OS X 10.10, Linux Mint 17, Windows 10 Pro TP
 
 

Quote:
And I figured once that compression is done the file is changed permanently.
No, decompressing should restore the original file, as it stood before the compressing. Compressing with WinZip, 7-Zip, ZPEG or others is only for storage, not for editing the file itself. If any bits are removed by the compression routine the decompression routine should restore them.

Saving images and their sizes is controlled by the format to be saved in, for example a .bmp converted to .jpg will result in a smaller file size and 'may' result is some loss of resolution, color layers, etc., which is fine for posting on the Internet or sending as attachments. For printing or archiving, the file type is important, want the best quality available which results in large file sizes with the camera's RAW format being quite large in comparison with other types, e.g. 20MB versus 3MB of a .jpg.
My System SpecsSystem Spec
01 Nov 2014   #6
LMiller7

Windows 7 Pro 64 bit
 
 

Unlike some other types of compression such as mp3, rar and zip are not lossy. A file compressed in this way is restored to the exact form it was before compression. This is critical for file types such as .exe where even a single bit wrong out of millions would likely render it useless.
My System SpecsSystem Spec
01 Nov 2014   #7
Alejandro85

Windows 7 Ultimate x64
 
 

As others have said, it's not the case with rar (or zip or 7z, for the matter), they all are effectively lossless like flac or png.

Multimedia compression algorithms are vastly different to those of WinRar. To begin with mp3 relies on an heavy assumption: that it always will be applied on audio data. It's a very important aspect of its operation. It's lossy not because it's just throws away random bits of data to make more effective compression, what it does is to analyze the audio stream and using the knowledge of the typical human earing characteristics it discards information in the frequency range where humans are less sensitive, so that only a musician is able to notice the difference. This characteristics is strongly influenced by the fact that the algorithm knows beforehand on what it will be working on, and makes assumptions and trade offs based on that data.

Png is also similar, it's optimized for photography and discards information that makes real-world images look almost the same while achieving an important size reduction. But the very same algorithm does disasters on screenshots, for example, with quite noticeable artifacts all over. This is the tradeoff when the assumptions aren't meet.

Rar files, or any other general purpose compression algorithm, does not have such privilege. It's designed to work on any piece of data, unknown beforehand so it can't make any guess on how the data will be used, or even what kind of data it is. Thus, the only safe move for it is to explicitly preserve each and every byte of the input in the final uncompressed output. This is the reason that it's often more inefficient for specific file types. For example, a rar'ed .bmp file will generally be bigger than converting it to png or jpg, for example. This is also the reason why rar is so ineffective with mp3 or mpg, because they've already been aggressively compressed by special-purpose algorithms before, and rar can barely find anything else to do.
My System SpecsSystem Spec
Reply

 Check Compression Level In An Existing .rar File?




Thread Tools Search this Thread
Search this Thread:

Advanced Search




Similar help and support threads
Thread Forum
Do you have a prefered file compression software or file format?
Iuse winrar and need to know if there are any differences between the different compression formats ( zip, rar, tar) and if one of them is more robust than the rest?
Backup and Restore
Replace default .pst file with existing .pst file
I upgraded from Vista Business to Seven Home Premium. Used Office 2007 in Vista and using it in Seven. In Vista, my .pst file was C:\Outlook\MyOutlookFolder.pst. Added it to Outlook using Data File Management, but none of my calendar entries appeared (my inbox and all my other folders are OK). When...
Microsoft Office
Strange File Structure on Top level of OS Drive.
Does something seem odd with this file structure? There's a ton of files listed in the top level directory that I would normally think should be down in the Windows level. The view here is with hidden files and folders OFF. I recently had an infection located in this same folder with a...
Software
File sorting - limited to one level now?
In Vista, I was able to sort files by date created, highlight the files I want, then sort again by name, and all the files I selected previously would still be highlighted, but now they're in numerical order. Win 7 won't let me apply that second level of sorting. It's either name or date, but not...
General Discussion
File Compression
In looking for a means to backup my movies volume (~750GB), prior to sending that hard drive in for RMA, I decided to see if I could place them on a smaller drive (500GB), first by using True Image's Cloning feature (I was hoping that it would be able to compress the files enough), which failed. ...
Performance & Maintenance


Our Sites

Site Links

About Us

Find Us

Windows 7 Forums is an independent web site and has not been authorized, sponsored, or otherwise approved by Microsoft Corporation. "Windows 7" and related materials are trademarks of Microsoft Corp.

Designer Media Ltd

All times are GMT -5. The time now is 13:46.

Twitter Facebook Google+



Windows 7 Forums

Seven Forums Android App Seven Forums IOS App