ZOOM H4n Material lost on SD Card

[Chris Kehnle]

Hi tucker,

Are these the instructions you followed? This is the post I found most helpful for my situation. (I unplugged the power while recording, not realizing the batteries were dead. ). I had been recording for about 17 minutes. Then not realizing what I had done, I continued to
Record on the card. When I followed the post below, I was able to see a lot of stuff on the card( even stuff I had deleted/ formatted off). I didn’t get my lost clip because I had ” recorded over it”, but this was my best shot, and hopefully can help you

David Blumenfeld Re: ZOOM H4n Material lost on SD Card
by David Blumenfeld on Oct 7, 2012 at 12:34:26 pm

I picked this up off of another post after my batteries died on Zoom 4hn at the end of a 1 hour interview. IT WORKS! Even if it reads 0 on your card!

https://zoomforum.us/viewtopic.php?f=15&t=17991

Dear H4n Mac users,

I thought all was lost. My batteries ran out during a shoot (phantom power drain horror) and when I got back to the studio the file came up as 0kB. But thanks to hints from forum member aumeta I’ve managed to recover it. I thought you all should know it can all be done on a mac using freeware. Follow these steps:

1. As soon as it happens remove the SD card and don’t use it. Unknowingly, I did use it, but for less time than I had previously recorded, so I was still able to rescue a large portion of my file. The SD card works a lot more like a tape than you might imagine. So when the batteries fail, it will start recording the next file at the start of the file that failed when your batteries went. This means if you’ve recorded, say, a 25 minute track, then the batteries have run out, and then you’ve recorded 2 more 2 minute tracks on the same card with new batteries, that you can still recover the last 21 minutes of your track. Clearly, it’s better to recover all of it, so next time, carry a spare SD card, and stop using the battery damaged one!

2. Back in the studio, plug in your SD card into the card reader so it mounts.

3. then open
Applications>Utilities>Terminal
What we’re going to do is unlock some advanced features on another utility Disk Utility

4. Once Terminal has started up copy and paste this in:
defaults write com.apple.DiskUtility advanced-image-options 1
then press return

5. Now open
Applications>Utilities>Disk Utility

6. Select your SD card in the list of drives, then click the New Image button

7. What we’re doing is making a copy of the entire SD card, including all the empty bits. This allows the audio program we’ll use which can read RAW files to read the entire disk image as one enormous audio file.
So, in the Image Format tab select “Entire Device” and have encryption set to “None” and save your disk image to a drive big enough to hold it.
instructions with pictures are here https://echoone.com/filejuicer/disk-images (ignore the last section about file juicer it will not help your problem

8. Now you’ve got a file that you can open in your audio program. One that can do it is a piece of freeware called Audacity which I found out from the forum post by johnsantic.
Download the Mac version from here: https://audacity.sourceforge.net/

9. Here I’ll adapt John Santic’s instructions from this post which saved some files for me which we’re’n’t 0kB (https://www.2090.org/zoom/bbs/viewtopic.php?f=15&t=14366)
“The normal way to load an audio file into Audacity is to use the typical “File > Open” command. But they have another way to read in a file in case the header is damaged or missing. This uses the “Project > Import Raw Data” command. The next step is to select your new disk image in the dialog box that opens.

10. Another dialog box should open which asks for audio parameters, this should be the same as the way in which you recorded the file:
In my case this was:

– Signed 24-bit PCM (ie 24 bit WAV on the zoom)
– Little-endian [this means the audio data in the file is least-significant-byte first – it will be the same whether you recorded at 24 or any other bit rate]
– 2 Channels (Stereo)
– Start offset = 910 [this is the normal size of an H4n header, you should also try 0 and 2 if you are at 24-bit, or 0, and 1 for 16-bit]
– Amount to import = 100%
– Sample rate = 48000

After you click “Import”, Audacity reads in the file. What you’ll probably find is large blocks of interference with audio files inbetween. If you find your lost recording, select that section, then use the command “File > Export” and save it under a different file name, with the same settings as your other original sound files. Joy! OK so you’ll probably lose a tiny bit at the end and at the start, but I’m sure you’ll live having recovered the vast majority of what you thought was lost forever

11. If you don’t find your audio file in there this time do not despair. Instead just go back to the start of part 10 and enter in a different start offset (0, 1 or 2) and you’ll find a different portion of the audio you recorded will appear. I found my lost file on the second attempt when I set it to 0. Just keep on trying.

I thought I’d messed up the whole project. Now I’m full of the joys of life, and thought I should share it with you all.

Ta,

James

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zoom1061
Post subject: Re: Ran out of Battery and found only a 0Kb file? There’s hoPosted: Wed Jul 11, 2012 4:11 pm

new to this board

Joined: Sun Jul 08, 2012 6:12 pm
Posts: 1
I just wanted to affirm Jimmybulb’s post. Thank you! and to anyone else who did the behind the scenes work to make recovery possible, you rock! I spent 4 hours troubleshooting and downloading random freeware programs, but when I found this post, all was saved except about 15 seconds that were somehow corrupted. I ran the process twice through to see if the file would come out clean but it didn’t so I’m guessing somewhere in the process of my Zoom H2 becoming unplugged, the file became corrupted. I’m not really sure. I was recording a wedding and it finished. Because my batteries were dead, I had confidently plugged my zoom H2 into a power strip thinking it was the ultimate, safe source of power. Well, the sound board just happened to be plugged into this power strip and the sound engineer unplugged it after the wedding. The zoom power was cut off before I could stop recording. Note to self – set up at least 2 layers of good quality audio backup if possible.

A couple helpful notes.
1. Don’t stop trying if you get an audacity file that is ALL interference. You probably got the audio parameters wrong. The sample rate, offset, stereo or mono, little endian all seems to matter. I tried multiple settings before I got the right one and sometimes the audio came out as all interference (LOUD interference) or super slow low voices.
2. All the freeware recovery programs I tried didn’t do what I wanted. Most recover deleted files, pics, etc.. not fix audio files without a header.
3. I tried 0 for the offset, and it came out as pure interference. 1 and 2 both worked in my case. I was recording 16bit, stereo, at 44kHz.
4. DEFINITELY choose a low percentage to import to test first. Setting it at 5% for about 7.4GB of a card only took about 30 sec to process on my macbook pro.

Good luck!
Nick

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[Tucker Tangeman]

I’m just getting back to this sorry! And thanks for the response, what I’m struggling are the values listed? I wasn’t recording wave but MP3 and I was wondering about the “24bit pcm”. On adobe audition and audacity there are other options for this field and I was trying to learn if any one had tried changing that value in accordance with the settings they recoded on the Zoom?

[Chris Kehnle]

To be honest I just followed the directions almost blindly and it worked.
They worked for me, but I couldn’t explain why. You’ve tried plugging in different numbers to match your bit rate right? Other than that, I’m not sure what to do. Sorry I can’t be more help, but maybe someone else will see your post and respond.

[Red-rob Rothkopf]

Hey Karl!

Firstly, I must say — NICE WORK! I worked in the technology field for 16 years coding in a variety of languages, sometimes digging into HEX to find bytes of data and massage data, code, whatever.

I’ve struggled on more than one occasion with lost interleaved data on Zoom R16. I use Windows and never thought of creating a disk image to start (I’m not sure how I’d even do this on Windows.. haven’t looked into it). When I analyzed chunks of files I had recovered and merged I never figured out the chunk size.. and without published specs on the actual file format eventually gave up. ☹

Just this past Friday I had someone unplug my R16 again.. and although I had fresh batteries (backup, yay!), by the time I noticed it was unplugged they too had died. And then it happened again Sat. with my Tascam DR-701d. ARGHHHH.

Thought #1: You suggested last year that automation was not likely possible due to not knowing the start of file… but I’m not so convinced. If a human can figure out the start of file, then we can build tools to help find that start of file, or actually find it. I know the Zoom R16 keeps “file directory” information somewhere, with the list of projects… maybe that also contains file-starts?

Although it’s been a bit of time, I’d be happy to attempt to build a recovery tool to automate things if an algorithm can be devised. This is a LONG OVERDUE tool, for both ZOOM, Tascam and other recorders.

Thought #2: Have you considered selling your recovery skills as a service? At least on THIS thread, you seem to be the de-facto expert. ☺

Whatcha think?
☺ Rob

[Tim Ellis]

I just registered to thank you, Karl. I accidentally deleted some files from my Zoom H5 recorder and the recovered files (recorded using MULTI mode) were all multiplexed like this. Using your steps I was able to successfully cleanly split the file into its two component parts.

In case anyone else comes here looking, the MULTI format file on the Zoom H5 had parts that were split every 32,768 (8000 hex) bytes. At the beginning of the section was an eight-byte string that began with the characters “data” and when I deleted those eight bytes and split
the file up every 32,768 bytes using HxD, everything went perfectly.

The one trick that threw me for a bit of a loop was that I didn’t realize that when you use “Extras -> File tools -> Split…” in HxD, it splits based on the file as-saved, not whatever is in the current view. I kept trying to delete the 8-byte “dataxxxx” part and then split but everything was slightly offset. It was because I wasn’t saving the file after deleting the leading 8 bytes.

Anyway, thanks again Karl!

[Carlo Siegfried]

He everyone, a few years later, same problem. Has anyone found a practical way to restore 0mb files recorded in 4 channel mode from an SD card used in a Zoom H4n? The disk-image-audacity-solution only gives me feedback and chopped up bits of my recording.
thank you so much
Carlo

[Adam Loveday-brown]

Hi All.

Creative Cow newb here so apologies if I get the etiquette wrong!

Same multi-track problem here, although recorded on a Zoom H6 this time.

Adobe audition was working better for me.
It seems that Karl Chelette is basically a genius and knows what to do!

Karl, any chance I can pay you to help me recover my audio? Or anyone else that gets it?
I’m all good up until the bit where you get super clever:

Then I made an image file of the test recording and opened it up in HXD hex editor. I found out that with my zoom r24 recorder, when recording, it records 393216 bytes of each channel sequentially and when done writes the wav header with data location, recording format etc. When turned off improperly the wav header is not written and the data that is there is in alternating blocks of each channel.
Using HXD hex editor I found the start of the data and saved this as a new file, which I then used the split option in HXD and split the file into chunks of 393216 bytes, named 0001 and up. Then I opened the folder with the file chunks into it and squised the screen down till I could view 2 rows of files, about 4,000 of them. Then I selected the odd row on the left and cut and pasted it into a new folder. Then using HXD, I concatenated (joined) the odd file numbers together, then did the same for the even ones. This left me with in my case, the data for both mono channels. Then I imported the test recording file in HXD and pasted the recovered data into the proper space, which was at 60000 hex location. The next thing I had to alter was the last 4 bytes before the data which tell the file length data. Repeated the same for the other channel then voila, both channels recovered, no echo, synced properly, 3 hours worth back!!!!!

[Carlo Siegfried]

Dear Adam!
Did you manage to make contact with Karl Chelette? I have the same problem and I am looking for someone who can fix it for me.
Thanks for letting me know!
All Best,
Carlo
siegfriedcarlo@gmail.com

[Ryan Elder]

I thought that with the ZOOM, that if the zoom is being fed electricity from an external source, that if the power is cut, the zoom will still go back to the battery source and stay on, using the batteries at that point.

Or am I wrong, and this is not how it works?

[Adam Loveday-brown]

Hi Carlo.

Sorry for the slow reply. I didn’t get hold of Karl unfortunately.

I’ve been to so many data recovery companies now it’s getting ridiculous. Zoom UK haven’t been able to help either. They said they would try and put me in contact with Zoom Japan but no dice yet. Zoom UK seemed to think this was a very unusual situation, I pointed out that it’s a common flaw in their systems. For me the unit didn’t loose power, I actually switched the unit off at the end of the recording and it shut down without saving the files properly. This really shouldn’t be physically possible if the files are not written, the unit should either warn you or just take longer to switch off.

Of about 100 different data recovery companies only one seems to actually understand the issue. They are based here in the UK and are called Ontrack.

They haven’t been successful yet but they are on the right path. I basically gave them all of the information on this thread and also did some successful recordings for reference.
We are up to this stage: “It’s more like I have a long audio that’s missing certain intervals, So can hear for 3 seconds then drops for 2 etc, so just need to find out the length in bytes before the next channel is stored, as on disk it’s not sequential.”

If successful I will post here. Not cheap either, £250. However I really, really need this audio so will keep going no matter what. @ Karl Chelette, there are a few of us out here who would gladly pay for you to work your magic!

Video production dude, London