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Topic: Creating par2 files for lossless collection (Read 6045 times) previous topic - next topic
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Creating par2 files for lossless collection

I have compressed my cd collection using Monkey's Audio. (single file for each album). I will be storing the backups on CD-R.

Now i want to create par2 files to be able to recover the files if errors starts appearing on the cds. I have downloaded QuickPar 0.8. Any suggestions on settings? I understand that the ideal block size would be 2048 bytes, but i am not even allowed to go that low (why?). Example: I have added a 360 mb ape file, and the smallest block size i am allowed to choose is 11 476 bytes. Then the estimated compute time is 53 hours (10% redunancy set). It is ok to spend some time, but 53 hours is....a bit too much perhaps.

I want to have good par2 files, but i won't spend that much time. Do you have any suggestion for settings i could use? My computer is old. PII 400mhz, 64 MB RAM.

Creating par2 files for lossless collection

Reply #1 –
It may be the limit on the number of par2 blocks which is limiting the min size.

There's a forum on using par2 with CDR and DVDR at http://www.quickpar.org.uk

Creating par2 files for lossless collection

Reply #2 –
Your block size is wayyy to small for what you're trying to do.  At the very minimum you should be going with 2 MB block sizes.  With file sizes on the order of 300+ MB (you said you're encoding an entire album to one file), you're probably safe with a block size about 10% of that (32 MB is a good choice).

Your computer's low amount of RAM is really going to limit how small a block size you can go with.  The excessive time estimates you got were probably due to massive swap file usage.

Creating par2 files for lossless collection

Reply #3 –
PAR2 is limited to a maximum of 32768 data blocks, so for a 360MB file that requires a block size of at least 11.25KB.

However, I would never recommend using such a high block count because the processing times will be very long.

It is however recommended that you pick a block size that is an exact multiple of 2048 bytes (which ensure that block boundaries are aligned with sector boundaries).

Creating par2 files for lossless collection

Reply #4 –
Quote
With file sizes on the order of 300+ MB (you said you're encoding an entire album to one file), you're probably safe with a block size about 10% of that (32 MB is a good choice).

DOH!

I forgot you're working with CD-R, so you'll usually fit only two, at most three album files.  32 MB block size would be too big for your needs.

1 or 2 MB block size is a good starting point for the files you're using.  When using QuickPar, I usually choose the block size by sliding the source block count to a point where the efficiency value below close to maximum.  When block size gets too large or too small, efficiency starts to drop quickly.  When multiple block sizes give you similar efficiency, you can go with a smaller block size (higher block count) for greater reliability vs increased processing time.  You should expect for a good compromise between size and reliability to take a while, like an hour or even longer (although certainly not 53+ hours).

Also, make sure that you use enough redundancy to let you fully reconstruct at least one file.

Of course, as Peter said the base block size (chosen in the options) should be 2048.

Creating par2 files for lossless collection

Reply #5 –
Yes yes, i have all this worked out. The thread is old, someone just added a reply for the first time today.

Creating par2 files for lossless collection

Reply #6 –
Quote
Yes yes, i have all this worked out. The thread is old, someone just added a reply for the first time today.

So, Garathor.  What settings did you decide to use?

Creating par2 files for lossless collection

Reply #7 –
Block size: 2048 * 500 = 1024000 (i would want it to be smaller, but my computer is old. I takes 2 hours to create a par2 fileset for each ape with my current settings)

Redunancy: about 20%

(1 recovery file)

Creating par2 files for lossless collection

Reply #8 –
What is your efficiency percentage at that setting?  I'm using block size of 102,400 (2048 * 50) with 10% redundancy and it takes my PC about 4 minutes on average per album to complete with average efficiency around 92%.

Creating par2 files for lossless collection

Reply #9 –
Usually 98-99% i think.

Creating par2 files for lossless collection

Reply #10 –
2 hours is the estimated time by QuickPar. I just tried creating a fileset, and it took something like 20 minutes.

Creating par2 files for lossless collection

Reply #11 –
Quote
Yes yes, i have all this worked out. The thread is old, someone just added a reply for the first time today.

Oops, just noticed the date...