Public bug reported:
System:
Ubuntu 26.04
dvdbackup 0.4.2-5build1
AMD 2700X / X470
I am using dvdbackup to try and dump a DVD disc which is partially
damaged. I am using the binary search bad-sector handling mode, which
appears to be unique to the Ubuntu version of dvdbackup (it isn't
present in the upstream source, it is added via a patch in Ubuntu
packaging).
I knew there were spots of bad data on the disc, and for much of the
backup process, this was being handled correctly.
However, at some point, the algorithm got stuck in an infinite loop
where the "jump ahead" count ends up at zero, so it just keeps reading
the same bad sector over and over and over.
You can see in the logs here that it was successfully jumping over bad
sectors, until it got to a point where it got stuck:
Error reading VTS_04_4.VOB at block 1827953
trying 463 blocks ahead
success, trying 231 blocks back (gap size: 463)
success, trying 116 blocks back (gap size: 232)
success, trying 58 blocks back (gap size: 116)
Error reading VTS_04_4.VOB at block 1827968, read error returned
trying 7 blocks ahead (gap size: 14)
success, trying 1 blocks back (gap size: 2)
11:17 [756/12917]
first readable block is 1569505, moving on (total skipped: 1)
Error reading VTS_03_3.VOB at block 1569553
trying 126 blocks ahead
Error reading VTS_03_3.VOB at block 1569679, read error returned
moving on, padding 126 blocks
Error reading VTS_03_3.VOB at block 1569679, read error returned
trying 0 blocks ahead
Error reading VTS_03_3.VOB at block 1569679, read error returned
moving on, padding 0 blocks
Error reading VTS_03_3.VOB at block 1569679, read error returned
trying 0 blocks ahead
Error reading VTS_03_3.VOB at block 1569679, read error returned
moving on, padding 0 blocks
Error reading VTS_03_3.VOB at block 1569679, read error returned
trying 0 blocks ahead
Error reading VTS_03_3.VOB at block 1569679, read error returned
moving on, padding 0 blocks
Error reading VTS_03_3.VOB at block 1569679, read error returned
trying 0 blocks ahead
Error reading VTS_03_3.VOB at block 1569679, read error returned
moving on, padding 0 blocks
Error reading VTS_03_3.VOB at block 1569679, read error returned
trying 0 blocks ahead
Error reading VTS_03_3.VOB at block 1569679, read error returned
moving on, padding 0 blocks
Error reading VTS_03_3.VOB at block 1569679, read error returned
trying 0 blocks ahead
It was like this for nearly an hour before I noticed, so I figure it was
never going to break out of the loop.
** Affects: dvdbackup (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2163186
Title:
Binary search error mode can get stuck in a 0-sector infinite loop
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