2005-11-02 Software DVD

Once again I am trying to copy some concert DVDs Claudia’s teacher made. Some of them have bad sectors. This makes me so tired.

I’m trying recoverdm again. One file was recovered effortlessly. The other file is still being read. This can take forever. Ugh.

recoverdm

Some googling also found ddrescue. That seems promising as well.

ddrescue

I liked this little tutorial: PGP signatures on open source software, and why you should check them. I needed it because I had forgotten how to download missing keys. I never worry about this anymore because it works so flawlessly using Thunderbird + Enigmail for email.

PGP signatures on open source software, and why you should check them

Thunderbird + Enigmail

• *Update**: The last file was a 46M file that proved impossible to recover using recoverdm because overnight the recovery process had managed to read 2.5M. I am not prepared to wait for days. So I interrupted the process and tried ddrescue instead.

recoverdm will read each sector, and when it gets an error, it will repeat the read six times, switch to raw mode, and try another six times. When there’s a large block of errors on the disk, it will take forever.

ddrescue will read blocks of data, and when it gets an error, it will skip the block, writing zeroes into the output file, and write the bad block into a logfile. Once it is done, it will try rereading the bad blocks from the logfile. You can stop the process and restart it, too, because of the logfile.

My current expectation is that ddrescue will be able to copy a first version of the 46M without problems, so that I can at least look at parts of the track and decide whether this is good enough or whether I need to spend more time on rescuing it. The first 2.5M I have seem to indicate that this is the *menu* file. It cannot be *that* important! 😄 I just hope players will be able to deal with zeroed blocks in the middle of a vob file. That would be very useful.

Incredible how quickly CDs and DVDs seem to decay. I remember the days when I felt that a CD was forever (compared to tapes and floppies).

• *Update**: I think ddrescue will take very long, too. 🙁 Many hours later, It’s at 22M. Which is about 10× faster than recoverdm (but will probably include many more bad sectors). (What’s the unit they use these days, blocks, sectors?)

• *Update**: I finally have the first version of the 46M I need. It even plays, with lots of static for the holes. ddrescue is still trying to do its job. I wonder what this does to the DVD drive – it must have been running for about 24h straight.

​#Software ​#DVD

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On Mac OS 10.4, figure out the device using `diskutil list`. Unmount it using `diskutil unmount /dev/disk3`. Twenty retries.

ddrescue -r 20 /dev/disk3 CD.img CD.log

– Alex Schroeder 2010-01-24 22:42 UTC

Alex Schroeder