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CD iso compression?

By ziggy2004 ยท 15 replies
Oct 8, 2004
  1. CD iso compression? RESOLVED

    Hello all,
    I would like to know what's up with iso files and the compression that they use, if any. I downloaded an iso file which was 691MB when I burn it to CD, however, when I extract the iso file with IsoBuster to a different file for editing, suddenly the size of the file is 1.34GB. What exactly is going on here? This has me completely baffled; :confused:

    I hope that someone can answer this for me because it doesn't make sense to me, as far as I know, you can't store 1.34GB of data on 1 CD.

    Thanx for any advice/enlightenment,
  2. RealBlackStuff

    RealBlackStuff TS Rookie Posts: 6,503

    A CD has its data put on there in an uninterrupted string, with no empty space or waste at all. When you extract with isobuster, it spreads the data over umpteen clusters, with a lot of waste in between.
    A CD just stores more efficiently than a HD.
  3. Mictlantecuhtli

    Mictlantecuhtli TS Evangelist Posts: 4,345   +11

    So you burned an image as a file into a CD, and uncompressed it afterwards? Sounds to me like it's a DVD image.
  4. Nic

    Nic TechSpot Paladin Posts: 1,549

    I think you are talking about one of the special CDs that have more than one version of a particular application present. If more than one application on that image file shares files with another, then rather than have two copies on the CD, it is possible (using special tools) to put just one file on the CD image and have the table of contents for each application point to the same physical file. This can save a lot of space. I believe Microsoft has been known to use this format/technique when putting multiple versions of SQL Server on one CD, when under normal circumstances these wouldn't fit. I've seen it several times with various software. The problem you have is that once you have extracted the files, you don't have a similar tool to put them back in the same way. What you have done is extract multiple copies of the various files that only existed as a single copy in the image. The size will therefore be much larger and will not fit on a 'normal' CD.

    It might help if you listed what is on the CD, but I figure I must be on the right track. If not, then please llist the programs on the CD.
  5. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,729   +409

    Ah, I hadn't thought of that Nic, that makes sense. I've seen some pirated versions of Office where there is 2 or 3 ways you can extract it with isobuster, one being with joliet filenames and then the old 8+3 filenames.
  6. ziggy2004

    ziggy2004 TS Rookie Topic Starter

    Hello all,
    Thanx for the advice/insight on the issue of .iso compression. Nic is correct as far as having multiple versions of OS's on the CD. I did actually find an article that explained what was happening to the data when you compress/optimize an image to be burned. There is actually only one(1) copy of any type of file and the rest are pointers to that file instead of having the same file numerous times on the CD.

    If anyone wants to read it, I'll try to find it again. I actually forgot about this post, otherwise I would have posted the link to the article right away for others to see/learn.

    The CD has a number of different bootable OS's and a variety of software for diagnosing/troubleshooting computer systems. When I got the iso file, it was labelled "Drive Image 7" and I wanted to try out this software for backing up my HDD. My opinion, it works great. However, I was mildly surprised at the number of other applications on the CD, all I wanted was the "Drive Image 7".

    If anyone has any advice as to how I can get rid of all that other stuff in the iso file, except Drive Image, of course, and still use the application properly that would be great.

    I can't seem to find the "Drive Image 7" application anywhere, I've read a lot of reviews on different software to backup your "System" HDD and Drive Image was highly recommended, however, PowerQuest, the original owner, was bought by Symantec some time ago and now I believe the Symantec is trying to incorporate Drive Image's capabilities into "Ghost".

    Thanx again,
  7. RealBlackStuff

    RealBlackStuff TS Rookie Posts: 6,503

    Drive Image 7 is also, and maybe better, known as Drive Image 2002
  8. ziggy2004

    ziggy2004 TS Rookie Topic Starter

    Thanx for the info, I didn't know that they were essentially the same thing. I thought the Drive Image 7 was the latest version that came out before the takeover of Symantec. I don't suppose you know where I can download a copy of Drive Image 2002?

    Thanx again,
    ziggy2004 :D
  9. Nic

    Nic TechSpot Paladin Posts: 1,549

    Drive Image 7 is a newer version (than Drive Image 2002) that came with a bootable CD based recovery environment. When Symantec bought PowerQuest they released a newer improved version called Ghost 9, which can now handle incremental backups as well as both ghost and drive image file formats.

    If the recovery environment for Drive Image 7 is on that bootable CD you have, then you're better leaving it as is rather than trying to reconstruct another bootable CD with Drive Image 7 on its own. It can be done, but it may prove a little tricky to get working correctly. If you don't have the recovery environment, then you might as well forget about using Drive Image 7, as it doesn't create bootable floppies, so you won't be able to restore your image without another OS in which to run the program.
  10. Yottcap

    Yottcap TS Rookie

    So, in regard to the original topic of this thread (CD iso compression?)...Nic, you mentioned "special tools" used to create that particular type of CD. Do you know where to obtain those "special tools" in order to create an ISO from the extracted files? I am having a similar issue to Ziggy2004's, but I need to actually create a new ISO after some changes to the extracted files.
  11. mrudhula

    mrudhula TS Rookie


    Hi friends this is mrudhula ...new member of this group .As i heard that it is eally of gud tech help ...but plz do help me in assisting me with few tips .
    i have a WIN 98 system i have a net connection n its like hell maintining ...the system virus ...'coz i format my system atleast 5 to 6 times a month n its so time consuming ..so plz lemme know wats the best site that proviodes me with the new virus updates ....so that i can down load the anti virus software online...i'll be more than n happy to the help.
    I thank you in advance for the help ....n hope my friends you will assist me ...
  12. Nic

    Nic TechSpot Paladin Posts: 1,549

    I believe Microsoft developed their own in-house tool to create this 'All-In-One' CD, but it hasn't been released for public use. However, I've seen it available on some web sites, though not recently. Try searching for 'All-In-One Maker' and see if you get lucky.
  13. zastron

    zastron TS Rookie

    Recovery environment

  14. Nic

    Nic TechSpot Paladin Posts: 1,549

  15. zastron

    zastron TS Rookie

    Thanks Nic.

    I'll take a look at it...
  16. aryan2006

    aryan2006 TS Rookie

    In some CDs the same file can be displayed in many folders even though only one copy is written to the CD file system. When you copy such a CD to your hard disk , multiple copies are created ( one copy in each of those folders ).
    So the size seems to increase.

    If you want to create such a cd ,you can try MagicISO maker
    ( www.magiciso.com )
    after creating a cd image go to File> properties > optimise and check the box
    "the same files are only allocated once". All duplicate file copies will be written to CD only once .

    You can download a freeware called MagicDisc ( from the same site ) using which you can compress ISO images into UIF format ( Universal Image Format ) which are much smaller than the ISO and can be directly loaded into a virtual drive.

    You can also try PowerISO ( www.poweriso.com ) which
    compresses ISO images to DAA format ( Direct Access Archive )

    Both DAA and UIF files are about 40 % smaller than ISO and can be directly loaded into a virtual drive , and accessed without decompressing.

    DAA is better ( faster & better compression ) than UIF

    PS : If you want to try PowerISO try version 2.8
    There are problems with version 3.0
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