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[pelago]

I have just started using Qwix and I was using it to play with an ISO that had been created with another program. I read about your optimized format and thought "I'll have a bit of that", so I set about optimizing this ISO.

I tried two different methods to convert this ISO. First I used Qwix to extract the ISO by using the Load ISO/Extract ISO option, then made a new ISO using the Create ISO/Local Folder button, browsing to the folder I just extracted the ISO into. I then noticed that there was a Create ISO/Convert ISO option which would let me browse to the old (non-Qwix-created) ISO, and create a new optimized version on the fly. Both methods created ISO files of the same size.

I wondered if there was a difference between the ISOs created by the two methods. From a Win2K cmd prompt, I did fc /b to the two files and it found some differences. As well as the expected differences at 0001001C (which is the date stamp of the created ISO, I believe) there were differences from 00084002 to 000840BE.

Being of a perfectionist nature, I wondered why there was a difference at this point, and which ISO was 'better'. In other words, is it better to extract and create, or just create directly from the original ISO, when trying to optimize ISOs? I'm running Win2k.

EDIT typos

[pelago]

Dragging up a rather old thread here, but I've just been doing some further investigating into this, which I thought might be of interest.

It turns out not to be a difference due to patching the xbe. The XBE in question is older than the feb 2003 media check so didn't need patching. I extracted both the ISO created directly from the older ISO, and the ISO created from an extraction of the older ISO, and the contents were identical in a binary comparison.

Looking at the bytes in the ISOs around 00084000 that were different, as you say it seems these are the root directory entries. It looks to my eyes that the only difference is that the directory entries are in a different order. I'm not sure why the orders would be different, but maybe it's just one of those 'random' things that happens when you read a directory. Neither of the two ISOs appeared to have the directory entries in alphabetical order, out of interest.

It seems the two ISOs are not materially different, so it doesn't really matter. However, for obsessive people like myself ;-) it would be nice if ISOs created by both methods were binary identical (apart from the date stamp stuff at 0001001C, of course). For example, I'm glad to hear that you are intending to patch XBEs when converting ISOs on the fly, even though that wasn't the cause of the difference this time.

[pelago]

No problem. PM me if you wish to.