What is a PAR file?
A .PAR(ity) file contains information on a group of files in an archive as well as information needed to complete a file that may have missing parts due to corruption, poster error, or if it just doesn't exist on the news server. Generally speaking, if you are missing 100mb from your archive, you need 100mb of .PAR2 files to fix the files. A good poster will post approx 10-15% of .PAR2 files relative to the archive size.
The process of creating PAR2 files breaks the archive files up into these blocks and stores enough information to verify a block is good and also information to fix a block that is bad. NewsBin's AutoPAR feature uses PAR2 files to determine which files belong in an archive and how many blocks need to be found to complete the archive.
If you want to know more about PAR2 files and how they work, then you can find a lot more information on the QuickPAR web site.
The previous section talked about the tasks that traditionally have to be performed after downloading files. As long as a file set is accompanied by PAR2 repair files then Newsbin can automate the following steps:
- Checking if all files are present in a file set
- Checking if the files are complete or are damaged
- Selecting for download the PAR2 files required to repair any damaged files
- Downloading the PAR2 files
- Repairing damaged files
- Decoding file set as long as it is a RAR, MasterSplitter or QuickPAR file set.
- Removing any redundant PAR2 files from the Scratch list
This set of facilities are known generically within newsbin as the AutoPAR set of facilities.
The pre-requisite for the AutoPAR facilities to work is the presence of the PAR2 repair files. If there is no PAR2 file present then AutoPAR is not triggered for that set of download files. However as virtually all none-trivial downloads are now accompanied by associated PAR2 files this turns out to not be much of a limitation.
|TipIf you would rather not use the Newsbin AutoPAR facility, then it can be disabled via the checkbox under Options->AutoPAR Options. This switches the AutoPAR facility off.|
Preparing for AutoPAR
The AutoPAR facility is basically automatic as long as you have queued the correct files. What you need to have done is:
- Queue the files to be downloaded
- Add the smallest PAR2 file added to the Download list. It does not matter if this file is positioned befoer or after the files to be downloaded.
- Add the remaining PAR2 files to the Scratch list.
If you have set the Add PAR's to Scratch checkbox set under Options->Switches then the above steps will happen automatically when you add an entry from Compact View that has PAR2 files included. It will also happen if you are using a NZB file and have the option to automatically add its contents to the Downlaod list set. However you need to check this as often in Compact view the PAR2 files are named slightly differently to the main files and need adding manually.
You also need to check the settings under options->AutoPAR settings. The options you are most likely want set are:
- AutoPAR enabled: You need to make sure that the AutoPAr facility is enabled under Options->AutoPAR options.
- Realtime Scan of Downloaded files: This option needs to be set for the AutoPAR automated processing to be activated (it has been removed as an option in the latest Newsbin releases so it is always set). Note that if it is not set the Decode does not happen automatically either, and you will have to trigger the AutoPAR process manually using the Refresh/Rescan button on the AutoPAR tab.
- Automatically Decode Complete files: This option needs to be set to get file sets automatically decoded (extracted). If it is not set then the automated processing will stop after checking and/or repairing the files.
- Delete RAR's and Pars after successful Decode: If this is set after Newsbin has successfully decoded the file set, then the files downloaded are deleted leaving just the files that resulted from the Decode action.
There are more options available for fine-tuning the AutoPAR behavior under Options->AutoPAR Options.
You can also disable the AutoPAR functionality for selected groups by setting this option under the Group Properties.
AutoPAR in Action
Most of the time the AutoPAR facility can be left to run itself.
If you have the AutoPAR tab visible then feedback is provided on what the AutoPAR facility is doing at any particular time. Each entry shows how complete the file is from an AutoPAR perspective. As new files are downloaded and checked the block counts will increment and the progress bar will move towards completion.
The status bar at the bottom of the AutoPAR tab will show a message indicating which action (if any) is currently being carried out.
AutoPAR automatically purges any entries that have been in the list longer than 2 weeks.
Problems using AutoPAR
The problems using AutoPAR fall into several broad categories:
AutoPAR will not work at all
Some people seem to have problems getting AutoPAR to work for them. Possible reasons are:
- The AutoPAR tab has been closed. If this happens then then the AutoPAR facility is disabled (versions prior to 5.53).
- The AutoPAR2.db3 file in the Newsbin DATA folder has become corrupted. If this happens then the only recourse is to delete this file with newsbin closed) and let Newsbin recreate it. Note that any existing AutoPAR entries will be lost if you do this.
AutoPAR will not start repairing/decoding a file This would normally mean that the AutoPAR facility does not have enough repair blocks to fix the file. Occasionally the repair blocks required are in the Scratch tab, but have not been added autoamtically to the Download tab. The solution is to move them to the download list manually.
AutoPAR will not repair a file: This has been known to happen. If it does then the best solution is to use QuickPAR to check/repair the files. It is also possible to get files that cannot be reapired even by QuickPAR. This is due to a very obscure bug in the algorithm used to create the PAR2 files.
AutoPAR repair fails
Occasionally the AutoPAR repair facility fails for some reason. If this happens the easiest way to fix this is to use QuickPAR to repair the file as QuickPAR has slightly more comprehensive facilities in this area than AutoPAR. Once the file has been repaired with QuickPAR, then you can select the Refresh/Rescan option from within AutoPar and it will detect that the files have been repaired, and move onto the Decode phase.
AutoPAR decode fails
This has been known to happen. If it does then the best solution is to use QuickPAR to check/repair the files and WinRAR to decode (extract) them.