Zoom R16 - Missing recording problem

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Allengrygierczyk
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Zoom R16 - Missing recording problem

Post by Allengrygierczyk » Mon Jan 29, 2018 11:36 am

Hey all,

Searched the internet far and wide for this issue, but was unable to find a solution (if any solution exists at all), hoping you guys can help me out (or worst case scenario confirm my suspicion that I'm screwed) .

I use a Zoom R16 to record a podcast with 5 different mics / channels. I always start out with an empty SD card and start a new project. In our last podcast, the battery went low 2 hours in, so I shutdown the R16, replaced the batteries and kept recording for another 2,5 hours.

Now for the problem: the SD card only shows the last 2,5 hours.
There are no corrupt files; the available data on the SD card corresponds correctly to 2,5 hours of wav files.

Reading up on some stuff and I suspect the R16 pretty much recorded over the existing project's wavs (although this does sound weird in my opinion). I probably didn't make a new project after the battery switch (not entirely sure anymore), but I never suspected this would cause the R16 to "dub" over the existing wav files.

If this is the case, is there any way to retrieve the original first two hours?

Another option might be that the R16 got shut down after the two first hours, before stopping the recording (I wasn't in control of the R16 at the moment). But would this cause the files to be completely gone? Wouldn't there be corrupt files of some kind in that case?

Thanks in advance,

Allen
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Wulfraed
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Re: Zoom R16 - Missing recording problem

Post by Wulfraed » Mon Jan 29, 2018 2:29 pm

Read the second bullet under HINT on page 22 of the manual. Or the entire NOTE on the same page.

I would not hope for any recovery system. Depending on how the SD card internal logic was rigged, the odds are good that the allocation units (SD cards do I/O /in/ large chunks -- and has to erase such a chunk before it can write new data on it) have been erased and put on a "free to allocate" list If they haven't been erased (and more -- did not get reallocated for part of the second session) they may contain sectors of all the former tracks interleaved at whatever rate the R16 flushed to "disk". EG: SD card allocation unit is say, 1MB, FAT file system is using clusters of 32kB -- so 32 FAT clusters per allocation unit. You were recording 5 tracks, so an allocation unit holds 6 interleaved (12345, 12345, ...) sets of data, and part of 2 tracks of data with the rest in another allocation unit.

If you'd stopped before the second session had written anything, there might be a chance -- the R16 would have marked the files free in the FAT, but the card wouldn't have done any allocation close/open on the data; so recovery software would have been able to find the data pointers in the directory. Once the SD card does an allocation mapping, the FAT pointers would no longer be pointing to the same units. The data may be on the card, if the card does "erase before use" (rather than "erase on free"), but those allocation units may not even be visible (the card could keep a small list of allocation units that are "spares" and do not count in the size of the card).



Note: this behavior was changed for the R24 which can have "always new" set on each track in place of "overwrite". The R16 requires the operator to deliberately "unassign" existing files if the content should be saved when starting another recording session.

The faster way (rather than unassign each track) would have been to shutdown, swap power, start, CREATE NEW PROJECT, CONTINUE (ie: use the settings of the previous project).
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