Difference in Compressed Disk Image (DAA) & Normal ISO?

Hello guys!

I had always been using ISO format to make an image of a disk. Recently I came across a file type called DAA, created by PowerISO. It claimed that it can create images in compressed format, thereby taking less space. Now, what actually is the technology behind it. Does this image type is the same as our normal compressed files (ZIP/RAR). If so, I am sure whenever we mount this kind of an image, it will first be extracted somewhere in a temp folder before we can use it, thereby making it a slow process.

Kindly clearify…


Looks like PowerISO FAQ covers most of your questions… :slight_smile:

For compatibility reasons only use well known image formats in future. :wink: DAA is not one of them.

Thank a lot… It did help…

One more doubt… If I make a image file in DAA format (compressed) out of a few picture and video files, will the quality of the videos/pictures suffer because of the compression…

There are two different types of “compression”:

[B]Lossless compression[/B]
The original data is preserved 100%.
This is the sort of compression used by e.g. Zip, RAR, and the DAA format.

[B]Lossy compression[/B]
The original data is changed in a way that hopefully is as close to the quality of the original material as possible. This is only meaningful for compressing pictures, audio and video, and it cannot be used on other data.
This is the sort of compression that is used in MP3 and WMA music files, DVD Video (e.g. MPEG2 for Video and AC3 for Audio), JPEG photos etc.

As a general rule, once you have compressed something you will not be able to compress it (much) further with a lossless compression technique, so it doesn’t make any sense trying to store your DVD Video as a DAA image instead of an ISO image.

It’s possible to further compress something that has been compressed by lossy compression, by using further lossy compression however, but that will eventually lead to visible or audible loss of quality.

Thanks DrageMester! Good explanation…