DVD Patcher FAQ

This is the DVDPatcher FAQ page.  This is a new program so there are no questions so far let alone frequently asked ones however here are some questions that you might ask if had the chance.

1. Can DVD work on CD's and other discs: Yes it can.  Although it is set up to assume folders for movie DVD's it can work on any disc that you can copy with the normal windows copy functions.  This could even include failing hard discs (but not tested).  It won't help on music CD's however.  ISOBuster is program you may find useful (not free).

2. If I just recover the data and burn it to a new DVD will it play better than the original: (Skip steps 2 and 3) Generally yes.  When your DVD player comes across a bad spot on a DVD it will use it's error correction routines to try and work out what is missing, this takes time and the picture may freeze while it happens. When you copy the data off your DVD onto the computer has already done this recovery process. Assuming you made a good burn of the new DVD you will just just get a blank screen and no audio - the duration of this very much depends on how bad the original DVD was.

3. If I read the disc again will the bad sectors be the same: Yes and no.  If you have a scratch or bad patch on you DVD then the errors will be centered around it. If your stars are in alignment, or more precisely the laser in your DVD drive and the tracks on the disc align minutely differently it may be possible to get a good read for sectors that previously were bad.  You need to examine the DVDpatcher log and it if you are lucky you can edit the .bsl files for patching between the sets of recovered files.  You are only likely to be lucky for small numbers of read errors.  Take my advice on playing it cool.

4.So if I might get good reading next time can I try my faulty DVD as the recovery source (Step 2)?: Yes, by all means give it a try, you may get lucky and it will save reading the whole disc again - but expect disappointment - but then again you could comeback later or tomorrow when you computer has cooled down.

5. Do I need to save the files I wish to patch at the same time as I save the bad sector list (.bsl) file?: Yes it is advisable.  There is no guarantee that you will get the exact same bad sectors the next time you read, you may get less and you may get more for the reasons outlined above.

6. Should I try a different DVD drive: Yes should give it a try if have access to another drive or computer, especially if you drive is a cheaper model. Some drives and brands are better than others - or just different. The more expensive name brands tend to give more reliable results. Again remember: Play it cool.

7.How do I know my friend has the exact same disc to give me data from: With commercial DVD's you can be reasonably sure if they are the same release. With 'Bootlegs' or unofficial you can never be sure. Choose Tools|File info and copy and paste the file size information in the log screen for email.  If the files are the same size you should be OK but nothing is guaranteed. You can get md5summer from http://www.md5summer.org/ Assuming that not every file on your DVD bad you can compare the MD5 checksum output of youir DVD and your friends good copy - obviously you can't compare for the bad files.    

8. Why does Reading a DVD file with Errors seem to take for ever?: On your DVD about 10% (very roughly) of the information is error correcting (CRC) data.  This data is cunningly arranged so as to be spread over the disc in a way that in can help correct a bad spot physically far away from it's location. The tradeoff is that it takes a lot of calculation to work back through error correcting data to generate good data for the bad spot.  This happens in the drive itself and can take a long time for each read request from the drive.  If you read with a large block size setting the DVD will be processed quicker but when an error occurs you will have a large chunk of missing data.  A small Block size will probably recover more data but take longer because it makes more read requests.  Progressively reduce the Blocksize in subsequent runs of DVDPatcher to get the trade off that suits you and go to single file mode if not all files are bad.

9. A DVD plays badly on my player but is OK on my PC and I can copy it, What's Happening???: Burn a new copy - at 4x and on brand of DVD you have found to be reliable in your player. Even though a DVD seems OK for the PC some bits may be marginal and your player can't read it so well or at all.  This may apply especially to older players.

10. I try to stop reading a bad DVD but it takes ages for DVD patcher to stop?: In early versions DVD Patcher waits for a read request to complete before checking for user input so it has to wait for the drive to decide it has done it's best on each read request which means executing the set number of hardware retries. Later versions may improve on this.

11. So is there any other way to interrupt this process?: Yes, just open the disc tray with the button on it. You can restart from the same place if you need to after e.g. cleaning the disc.

12. The .bsd file of replacement data is several Mb, too big for a single email, can I split it?: Yes, but by making several .bsl files. Open the .bsl file in a text editor and make several files containing the data, each file must contain the blocksize, the file name to extract from and the a sector list.  Make as many .bsl files as you need for convenience (with different names) and run DVDPatcher for each file. Send back the .bsl files with the matching .bsd files.

13. Can DVDPatcher read from copy protected disc?: No, it uses normal access to the disc and cannot bypass copy protection.

Last Updated 8 Aug 2008