dumping bbc micro discs

All questions regarding the dumping of media go here.
User avatar
mr.vince
Posts: 2135
Joined: Tue Oct 05, 2010 5:48 pm

dumping bbc micro discs

Post by mr.vince »

You are right... It should not matter what you dump when generating raw (stream) files.

However, due to the fragile nature of the medium, reading errors occur. You would be unable to notice damaged areas if you would be reading raw only. Now by specifying a guide format, DTC has a chance to verify raw data against a scheme. This way only tracks in an alien format (e.g. copy protection) must be read blindly. All standard data can be verified and thus corrected as needed. The drawback is that protected tracks which are based on the standard you verify against might trigger a bad read and might therefore be retried unnecessarily. This is a small price to pay speed wise.

TeaRex
Posts: 120
Joined: Tue Nov 30, 2010 5:36 am

Re: dumping bbc micro discs

Post by TeaRex »

A quick note from the sideline: -i3 vs. -i4 is FM vs MFM. For every sector of data, only one of them (at most) can work. It's not about large vs. small IPFs, it's about two different ways of recording data. Think of a piece of text that has some languge mixing: Any character will be either a normal English letter or a Chinese character, or possibly something else altogether (say Greek), but none will be English AND Chinese at the same time. And most texts will contain only (or mostly) one kind, or only the other. Some texts will use a mix but that is fairly rare. With floppy disks it's about the same. Many will be either entirely FM (readable by -i3) or MFM (readable by -i4), but not both. Some will mix MFM and FM sectors, but any one sector can only be either FM or MFM, so for any one sector, either -i3 will read it correctly or -i4, or maybe none of them (for example standard Commodore 64 sectors are neither), but never both.

ELITE
Posts: 8
Joined: Wed Apr 25, 2012 11:54 pm

Re: dumping bbc micro discs

Post by ELITE »

So taing a crude approach, is it possible to make an image of a protected amiga disc using the fm mode( kryoflux would would see all the tracks as alien and so protected even though some might not be) & submit the stream file to you & say it is for a an amiga disc nad when you make the ipf it will still be a perfect image of the original?

Similarly, I should be able to make a sgtream file of the bbc discs using any setting( eg atari, amiga etc), and any sectors not recognised as consistant with format(most if not all will be seen as protected) & you can still make ipf taht can be witten back to disc and run perfectly on bbc?
thanks

User avatar
Interceptor
Posts: 58
Joined: Wed Oct 06, 2010 10:17 am

dumping bbc micro discs

Post by Interceptor »

So long as you specify -i0 and -i2 then it produces the stream files which we use for analysis. Specifying -i3 or -i4 or whatever I. Addition ALSO checks and tries to produce the relevant image files for you, but we still use the stream files for analysis.

If you ONLY specify -i3 or -i4 then we don't get a stream file, so we can't do much from a preservation point of view.

I haven't read the whole thread so this may have been addressed already ;)

Post Reply