I own a slightly scratched BD that I am trying to backup with the method recommended here — first use makemkvcon to “bless” the disc, then ddrescue -b2048 to make an ISO copy. ddrescue completes with 0 errors, and reports 100% rescued (sometimes with a few initial read errors that are fixed on retry). But the resulting ISO file still reports hashcheck errors when I try to back it up with makemkv (whether by pointing makemkv directly at the ISO, or mounting the ISO via loop back and pointing makemkv at a copy of the mounted directory along with a copy discattd.dat that makemkv generated earlier.
The hashcheck errors start about 15% of the way in and then the backup fails.
Same result using mplayer or bluray_copy pointed at the same ISO file.
Any idea to troubleshoot? Is there some way a 100% successful ddrescue could still be saving bad data off the disc?
I just noticed that after using ddrescue three times to generate an ISO on this same disc, with 100% success each time, the three different ISO files have different md5sums. So clearly something is going on where ddrescue is not returning the same data each time notwithstanding finding no errors.
Example errors on processing:
Code: Select all
The source file '/BDMV/STREAM/00010.m2ts' is corrupt or invalid at offset 1187463168, attempting to work around
DEBUG: Code 179 at %-Nz)AJ{%l]mS>+:6G!g:213133250
DEBUG: Code 0 at <|8L(k"IL<"*sQUDi1;f:213131157
DEBUG: Code 0 at <|8L(k"IL<"*sQUDi1;f:213131272
DEBUG: Code 579816 at <|8L(k"IL<"*sQUDi1;f:121261773
DEBUG: Code 0 at "<}&y)/QPll3W.ITZ7Y<&:213129984
DEBUG: Code 0 at b3O_v@D+A?$gJfkWPc.et:213137068
DEBUG: Code 1 at 1WA)q~a}1=@~!1!@:213132537
DEBUG: Code 0 at b3O_v@D+A?$gJfkWPc.et:213137068
DEBUG: Code 0 at b3O_v@D+A?$gJfkWPc.et:213137068
LIBMKV_TRACE: Exception: Error while reading input
The source file '/BDMV/STREAM/00010.m2ts' is corrupt or invalid at offset 1190547456, attempting to work around
The source file '/BDMV/STREAM/00010.m2ts' is corrupt or invalid at offset 1187463168, attempting to work around