[parchive-devel] public new PAR3 proposal

[<te...@ma...>]

Hello, parchive developers.
 I am Yutaka Sawada.
I public my new PAR3 proposal on my web-site. 
(URL: "http://hp.vector.co.jp/authors/VA021385/".) 
The specification and sample application are included in MultiPar v1.1.7.1. 
PAR3 is designed to be an upgrade from PAR2. 
It is faster, smaller recovery file, more reliable verification, 
and will give more chance of recovery. 

* faster
This is done by FFT.
I owe to Michael Niedermayer in the implementation of RS_FFT code very much.

* smaller
This is done by variable size packet header and smaller checksum.

* more reliable
While PAR2 uses MD5 and CRC-32 to check the integrity of input files, 
PAR3 uses MD5, CRC-32, and CRC-64. 
However PAR3 uses 12-byte checksum for file slices, 
miss-detection can be recovered by Reed-Solomon Error Correction Codes later. 
On the other hand, however PAR2 uses 20-byte checksum for file slices, 
miss-detection will cause recovering failure in Reed-Solomon Erasure Correction Codes. 

* more chance
PAR3 can use partially damaged slices by Reed-Solomon Error Correction Codes. 
In PAR2, only a few bytes error makes the whole slice un-available. 
As Error Correction is 5-10 times slower than Erasure Correction, 
this feature should be used only when normal Erasure Correction can not repair the damage. 

Best regards,
Yutaka Sawada