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Recovering FLAC's deleted from hard drive, deleted FLAC's and then recoverd turn out corrupted
eveafterdark
post Jan 20 2013, 19:43
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Hello everyone
some time ago I had - amongst other stuff - a part of my flac collection (ca. 200 gb) accidentally deleted from my external hard drive (don't ask how, I "experimented" with some drivers for my VAIO bluetooth and suddenly on opening one, I just noticed files being deleted - just saw as folders disappear one by one in the hard drive window, only managed to plug out the disk to limit my losses).
anyway, I bought a software which I used to recover photos, mp3's, videos in different formats, lots of kinds of other files/formats and the problem is with the flac files.
first of all, the recovery software sees all the flac's (and other lossless) as "probably overwritten." this is strange because for instance some of the albums were copied to the disk just before the deletion, and generally, this was just a storage disk, not much copy/cut/paste/delete/save was going on there, except from putting the stuff there once and for good.
of course, I know that some of the files must be overwritten, I mean, properly overwritten but my point is, some of the files can't just be overwritten (in terms of how saving on hd works). besides, inside the same music folders where the flacs appear corrupted, there's bunch of other files, like art work for example which are not corrupted and were recoverd completeley.
now, I don't know how about the recovery software seeing the FLAC (and other lossless) files as "probably overwritten" I asked that question to the manufacturer, but haven't got the answer.

SO, my question to you guys is: are FLACS,APE's etc prone to getting corrupted when deleted and recovered? (maybe because of how they're built - MD5, CRC - these are just my guesses) and therefore the damage is permanent? anyone had similiar experience? or is there a way to repair lossless files?

Some details on what I tried:
- any action in foobar (like opening such flac, veryfying integrity) just gives me :(Unsupported format or corrupted file)
- in dbpoweramp try to convert it to wave or test coversion: Information converting to Wave, md5 did not match decoded data, file is corrupt.
- in dbpoweramp try to convert it to flac: Error input channel count more than FLAC can handle. [clEncoder::BeginConversion]
- audio tester - 1 file scanned, 1 file failed: (LOST_SYNC @ 0m 00s); the same with FLAC TESTER.
- FLAC FRONTEND: even with the errors option ticked it says: Run-time error '75 path/file access error

also I opened the flacs (but only e few of them, because this is where chinesse begins to me ;-) and simply lost hope ) with hex editor looking for the flac sequence numbers but I couldn't find one proper sequence

I'll be happy to know if I'm just wasting my time
thx in advance
eveafterdark
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db1989
post Jan 20 2013, 19:57
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QUOTE (eveafterdark @ Jan 20 2013, 18:43) *
of course, I know that some of the files must be overwritten, I mean, properly overwritten
Yes. Deleted files are not normally physically deleted but simply have their allocated space freed to be usable for data from subsequently written files.

QUOTE
but my point is, some of the files can't just be overwritten (in terms of how saving on hd works). besides, inside the same music folders where the flacs appear corrupted, there's bunch of other files, like art work for example which are not corrupted and were recoverd completeley.
Assuming you mean that they couldn’t be overwritten because of the short space of time between your accidental deletion and attempt to recover them, then do you have any other processes that may have written to the external HD in the interim? If you are really confident that overwriting is highly unlikely, could you try using another program to attempt the recovery? Various free ones exist.

In general, larger files such as those of lossless audio are even more likely to be overwritten, since, upon deletion, they represent larger contiguous areas of free space, which will be preferred by the OS writing subsequent files to avoid fragmentation.

QUOTE
SO, my question to you guys is: are FLACS,APE's etc prone to getting corrupted when deleted and recovered? (maybe because of how they're built - MD5, CRC - these are just my guesses) and therefore the damage is permanent?
Not any more prone than any other deleted file. I am not aware of the specifics, but freed space will be used by the OS as it sees fit, based upon sizes of blocks, proximity to existing blocks of already present files, etc.

Edit: Well, actually, yes, if you are asking whether encoded/compressed data that relies upon blocks, RLE, etc. is more susceptible to serious/irreparable damage than uncompressed, linearly stored files would be, then that is true. A single byte changed in a compressed stream may damage an entire adjacent region or (I imagine, in extreme circumstances) the entire stream. In contrast, in an uncompressed stream, you could just ignore or amend that byte, and its neighbours would be unaffected.

QUOTE
anyone had similiar experience? or is there a way to repair lossless files?
Perhaps, although I wouldn’t get your hopes up if it turns out that the files in question were indeed overwritten, as entire parts are likely to have been changed, possibly including quite essential data. You may be able to recover certain spans of files, but I wouldn’t hold your breath that you’ll be able to get (m)any back in their entirety (edit: and regions that you do get back may not be recoverable for playback, anyway). I hope they’re not as badly overwritten as the program suggested, of course. smile.gif

This post has been edited by db1989: Jan 20 2013, 20:05
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