xcd + ogm = unbelievable -- i love it!

[kilg0r3]

just wanted to get that known.

i have an xcd here which has a deep radial (not tangential) scratch of about 1 cm on the recording surface that can even be seen from both sides. so, tha data on that portion is definitely destroyed. when i saw that i got a big panic. for everybody says that xcd has no error protection. right, but ogm has, and , as it seems, it works great!

despite the damage. the thing seems to play without visible jerks or anything. i just couldn't believe it but, well, great work guys. cheers cheers cheers!

[gabest]

Maybe you wouldn't be able to play it back in case it had error protection. It would just tell you that the disc is damaged and quit :P

[Koepi]

Trying to undermine our backup attempts, gabest?

Now this is really, really odd.

If there were backup files, too, it wouldn't reject the disc.

PURE BS!

It would just insure that the vital parts of the stream are intact in order to keep it playable. So DON'T ANYONE BELIEVE WHAT GABEST WRITES HERE, XCD WITH ERROR PROTECTION DOES _NOT_ REFUSE TOP PLAY THESE DISCS!

Koepi

[gabest]

I don't understand you. I just wanted to write that he may be lucky with the xcd format, because in the normal way windows would have surely refused to read the disc with such a big scratch on it.

[avih]

i think that theoretically, if part of the file is damaged, it shouldn't be a problem to read the REST of the file. but anyway, the backup sections (at least for ogm) is only the 1st 64k of the file, such that all the crucial (file info) data is preserved. the video itself has no backups at all (except for possibly 'internal' format protections), just like in vcd or svcd.

[kilg0r3]

hey what is happening here? i must contact doom9. for there seems to be a negativizer dongle installed on the forum system.

i come here to throw around a little praise. And, what happens? the other two guys start insulting each other; well nearly ... never again will i say something positive about anything ;)

:) :) :) :) :) :) :) :)


-----
it is so nice to be allowed to be here ( no i don't mean the forum; NOT ONLY ...
if you make my day i'll try to make yours too ... :) :)

[DeXT]

I think it was just a misunderstanding between gabest & Koepi. Gabest argument was theoretically right, but he was referring to a 'normal' Mode 1 disc and not XCD w/backups. A higher protection layer means a higher degree of expected reliability, i.e. the file would refuse to load if error correction was impossible (as an example, you should never be able to load a corrupt executable file, but you can live with a video file with glitches). However Koepi thought he was attacking the XCD backup system :)

So the fact is, XCD has the best of both worlds, it provides reliability on vital parts of the file and error concealment on media content (a note: it should, however, allow reading of vital parts with errors when the backup is totally unreadable, to allow at least a partial playing -- this is always better than no playing at all and a nice error message).

[soujir0u]

So does this mean XCD is already reliable enough for storing movie archives?

[Koepi]

I wouldn't suggest that. Wait until the backupcreator is used.

Regards,
Koepi

[SirDavidGuy]

everybody says that xcd has no error protection.

Everyone's wrong, it does.

What would be a good idea is to:

A. Interleave the data (eg. have 1 bad byte in 30 frames instead of 30 bad bytes in one frame)

B. Keep RS codes in the Subchannels (Although, these wouldn't help to much, with only 96 bytes.

[mustaneekeri]

Originally posted by Koepi
I wouldn't suggest that. Wait until the backupcreator is used.

Regards,
Koepi

R we goint to c a Backupcreator in this millenia?
(Not to discredit ur efforts that u already have done to benefit our backup needs and without pay, of which im truly grateful :D ).

[mustaneekeri]

Koepi, can u answer me plz?

[avih]

koepi's backup creator is on the xcd cvs on sourceforge for some weeks now (sources). it's been ready for about a year now. the problem is that the xcdlib can't utilize these yet, so we didn't publish them.

feel free to grab the latest (partially working) sources of xcd from the cvs, and implement the backup functionality according to the spec on http://xcd.sf.net.