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forum, ECC - documents, limits, disc reading

 
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mhajicek



Joined: 23 Mar 2008
Posts: 4

PostPosted: Sun Mar 23, 2008 11:46 am    Post subject: forum, ECC - documents, limits, disc reading Reply with quote

First of all, thanks for your free ICE ECC prog. I'm new to these things and it's really interesting and usefull. Few questions and suggestion:

1-consider splitting the main forum so that every program will have it's own space. Even now searching info related to one prog takes time and it will be worse as the forum will grow in time.

2-could you add some short clear explanation to the main web - how ICEECC works and how to determine how many blocks and redundancy user needs for his case? I have finally find this by reading all the forum through, but not easy and still not sure if i understand it.
So this is what i think i know, please correct me if i'm wrong: ICEECC/R-S code need one good block of .ecc file for each bad datafile block to be corrected, and whole block is bad even if one bit is bad. So if errors will be widespread through all blocks it will be impossible to correct it even if i would have say 20% redundancy and sum of bad bytes would be only 5% of total amount of data, right? So number of blocks is extremely important?
And - you reccommended somewhere for CD/DVD 20-30% redundancy, but with larger blocks? Wouldn't be better for typical discs to use 2-5% redundancy with maximum number of blocks? (i know that it needs several hours for computation, but night is long enough :-) )

3-Why max number of blocks is 32767? Is it R-S code limit? If so, wouldn't it be a good idea for large dataset to split it to several parts before running ICEECC to get better protection? (DVD-DL, Bluray, etc.)

4-Do you plan to add dics reading ability to your prog? Then user will not need other software. (with eg. setting max read speed, number of retries, jumping at error, filling error places with zeros, or so)

5-If disc TOC is bad, everuthing is lost, right?

Thanks.
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ICE Graphics
Site Admin


Joined: 31 Mar 2003
Posts: 430

PostPosted: Mon Mar 24, 2008 8:14 am    Post subject: Re: forum, ECC - documents, limits, disc reading Reply with quote

mhajicek wrote:
2-could you add some short clear explanation to the main web - how ICEECC works and how to determine how many blocks and redundancy user needs for his case? I have finally find this by reading all the forum through, but not easy and still not sure if i understand it.

About main ideas, how work ICE ECC or similar programs you can read here: http://en.wikipedia.org/wiki/Parchive or here: http://www.techsono.com/faq/par.html

You can use almost any redundancy. I can recommend for store on HDD redundancy 2-5%. For CD/DVD disks 20-30%.

mhajicek wrote:
So this is what i think i know, please correct me if i'm wrong: ICEECC/R-S code need one good block of .ecc file for each bad datafile block to be corrected, and whole block is bad even if one bit is bad. So if errors will be widespread through all blocks it will be impossible to correct it even if i would have say 20% redundancy and sum of bad bytes would be only 5% of total amount of data, right?

Yes. But this is very rare case. Usually errors are grouped.

mhajicek wrote:
So number of blocks is extremely important?

Number of blocks is important, but not extremely important. I can recommend to use maximum possible blocks with reasonable compute time. I mean select required redundancy, after what choose number of blocks so that time of creation ECC files was not too big.

mhajicek wrote:
And - you reccommended somewhere for CD/DVD 20-30% redundancy, but with larger blocks?

For CD/DVD block size is not too important. Usually errors on disks are grouped by large blocks.

mhajicek wrote:
Wouldn't be better for typical discs to use 2-5% redundancy with maximum number of blocks? (i know that it needs several hours for computation, but night is long enough Smile )

I do not think, that it will be better

mhajicek wrote:
3-Why max number of blocks is 32767? Is it R-S code limit?

Yes. And it is not necessary to use more blocks.

mhajicek wrote:
If so, wouldn't it be a good idea for large dataset to split it to several parts before running ICEECC to get better protection? (DVD-DL, Bluray, etc.)

ICE ECC assumes, that errors are usually grouped in the big blocks. The real life shows, that this assumption is true in most cases.

Splitting data to parts is not good idea. ICE ECC use global recovery algorithm. It's mean, what recovery block can recover any damaged block. If you will split you data, recover block will recover only data in one splitted section.

mhajicek wrote:
4-Do you plan to add dics reading ability to your prog? Then user will not need other software. (with eg. setting max read speed, number of retries, jumping at error, filling error places with zeros, or so)

We do not plan to add any read ability function. For CD/DVD recovery there are a lot of freeware solutions, like "Alcohol 52% Free Edition".

mhajicek wrote:
5-If disc TOC is bad, everuthing is lost, right?

If TOC is damaged, CD/DVD drive cannot even identify a disk. Also will not allow to read any byte from a disk.
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Telengard



Joined: 29 Jul 2007
Posts: 4
Location: USA

PostPosted: Wed Oct 22, 2008 6:39 pm    Post subject: Re: forum, ECC - documents, limits, disc reading Reply with quote

mhajicek wrote:

5-If disc TOC is bad, everuthing is lost, right?


Not necessarily, if you know about data recovery programs like ISOBuster. I believe it, and other CD/DVD recovery programs can read files from a disc with bad TOC.
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