User Tools

Site Tools


miscinformation

MiscInformation

This is precisely not the proper place for this comment but I thought I might start the ball rolling (my first contribution) with some ideas of things about MD that may give a clue to its operation. Of course this may be all old knowledge to you, so please tell me right away if that is the case.

Please, please, someone tell me the right place to put this. I have some ideas on how the encryption must work (as a result of some other accidents), and maybe will offer this as #2 in whatever the proper section is that you decide to save this.

Number 1

I am lucky/unlucky enough to be the owner of a HiMD recorder (NH700) with no overwrite head. The story can be found here:

http://forums.minidisc.org/index.php?showtopic=22161

(Sorry I will figure out how to embed links properly “later”). This machine has a few odd properties that it shares with any machine whose overwrite head is disconnected, bust or misaligned. One of these is that you can completely erase a disc but not write to it. This led me to write protect the disc I inserted into it. Whilst this disk was playing, suddenly I get the message about pressing Y to format the disk. The stuff in the german jottings mentioned something like this though I have to read more carefully. I instead took the disk out, and was (later) able to play the disk perfectly. However it suggests some weird things about the way the format works (and nothing to do with SonicStage).

Of course it is well known that a write-protected disk cannot be read from by Sonic Stage. Well - cannot be *uploaded* from.

I think these two observations (the write protect and the attempt to format during playback of write protected disk) are probably related. I would be willing to undertake some experiments if anyone here thinks that would advance the understanding a little more. Clearly an overwrite head that is completely missing is more “reliable” than a machine with an intermittent connection via a “dodgy” ribbon cable?

Number 2

Started with raintheory’s suggestion that one could change SonicStage to point to a URL of one’s own choosing

http://forums.minidisc.org/index.php?showtopic=20002

Specifically tweak #3.

I proceeded to point SS at a bunch of different places, in particular I tried D:\ (my hard disk). I worked hard to get the disk shown by Windows Explorer in Details view but no luck.

Somehow SS then became unstable (refused to boot with some sort of weird error that many people have reported 0x4e2E or something like that – I can find the details if it is important). So I tried to put it back, unfortunately something didn’t work right (I didn’t do the SI backup for SS), so without thinking about it too hard, I did a System Restore in Windows. I also followed the instructions to restore the OMGRIGHT folder.

http://forums.minidisc.org/index.php?showtopic=21640

Voila, now SonicStage works again, and all my music files were ok, EXCEPT the ones which had been generated between the time of the system (i.e. registry) backup and the time I crashed everything.

My deduction – the keys that SS relies upon (more about this but really we don’t care so much) which are stored probably in the hidden folder OMGRIGHT, are probably updated with time information (as well as, since everyone knows this, information about the computer and perhaps the Pentium serial # or similar information such as used by Windows Product Activation).

I think what is happening here is that SS is updating the keys using something like Perfect Forward Secrecy, where each key is generated from the previous one. Of course you cannot go back in time with this scheme, so changing the system clock, for example simply doesn’t work.

Just a glimmer of what might be going on.

Number 3

This one is straight from a post on MDCF. If you need or want, I can paste the whole thing in here since it is my words, hopefully MDCF not claiming copyright to them. It relates to the way that tracks are protected from editing (on the portable HiMD unit). I strongly suspect they use the same technique to mark tracks from SS.

http://forums.minidisc.org/index.php?showtopic=21684

And this restriction does not seem to apply to NetMD.

Number 4

This one definitely tells something about how untitled tracks are treated, at least by Sonic Stage. It may not have relevance to what this site is trying to do, but what the heck….

http://forums.minidisc.org/index.php?showtopic=22034

Number 5

When doing a large upload (say a file with an hour of music) from NetMD to SonicStage, using the RH1, the behaviour is apparently different from when a small upload takes place.

Normally SoS walks through the file “transferring” with gradually increasing percentage, and immediately concludes the operation. However when the file is large (not sure what the size criterion is) there is a second pass, which shows the percentages cycling from 0 a second time (reminds me of my Panasonic HD recorder making a DVD and finalizing it), lasting about a minute or more.

I think this may give some clue to the way that files too big for a single ???chunk are handled. It's not a function of editing - the entire hour of music was recorded in a single stream.

Stephen in Vancouver

miscinformation.txt · Last modified: 2009/07/21 15:47 by stephen