BBC Radio 5 Live Data Recovery

CDR's on air credit - Elis James and John Robins

During February 2020, Cheadle DATA Recovery Ltd performed a recovery for Dave Masterman, producer for BBC Radio 5 Live Elis James and John Robins show. They had lost three podcast recordings due to data corruption on an SD memory card. This happened because the audio recorder lost power mid recording. This, and CDR's involvement afterwards, is explained on the radio show (listen below, or via YouTube). An emergency 24 to 48-hour service was provided by CDR with a successful recovery. Full technical details of the SD card failure and the associated data recovery techniques can be found at the foot of this webpage - it proved a challenging case due to interleaving audio data.

From Twitter:

This is Dave. Dave came from Manchester to London to record Elis and I doing an escape room. Dave carried all the kit. Dave has a dislocated shoulder. Dave spent two hours with us escaping from a room. This is Dave realising it hadn’t recorded. #PrayForDavepic.twitter.com/s1kNdbgCsf
John Robins (@nomadicrevery) February 5, 2020

To follow on from my former friend’s kind tweet about today’s audio disaster (@nomadicrevery), I thought I may as well now share with you the corrupt audio we have as a result. This will play in my nightmares for the next five years. pic.twitter.com/Kl9qsQWvLZ
Dave Masterman (@Masterman) February 5, 2020

Technical Details

The above tweet is about the corrupted audio which the radio producer had extracted by his own data recovery attempt. It is not a sample rate problem but instead relates as to how the specific audio recorder stores data to the SD card. The portable audio recorder in use was a Zoom H4n audio recorder. This has the capability to record up to four audio streams simultaneously. It can be used with personal radio microphones so users can move freely whilst their individual voices are recorded. In the production edit, the separate audio files are played back simultaneously so that each person has the same level of volume.

File Allocation Table (FAT) corruption after power loss

The data loss was reported due to lack of battery power and the audio recorder suddenly losing power. As a consequence of this, the File Allocation Table (FAT) had become corrupt. On inspection of the SD card, it was clear that there were no folder or file name entries associated with the required data. Full sector-by-sector scans could not locate any reference to the required files in the FAT. The FAT defines the folder and filename structure, but also (critically) defines the location of files by LBA values and deals with any splitting of files if these are not written in sequential blocks in the SD card. Without the FAT it was necessary to perform a 'RAW' recovery and to locate files by file type (e.g. .WAV, .MP3 etc).

Interleaved audio streams

The garbled high-speed audio which can be heard on the radio show is because the recovery attempt made by the show's producer failed to take into account that the three audio streams were interleaved within the raw data. Whilst their 'RAW' recovery found the start of each file it could not take into account the method in which data was written to the SD card by the Zoom H4n audio recorder. Below are examples of working audio files from the Zoom audio recorder, which show this interleave between files.

Removal of the interleave

To obtain normal audio playback it was necessary to take each of the "RAW" .WAV files in the recovery, and then write a script to separate the three streams of audio. Essentially the first 64 sectors of data were extracted to create audio 'stream 1', the following 64 sectors of data to create 'stream 2', and the third 64 sectors to create 'stream 3'. This process was repeated over and over again until each of the three audio streams were fully assembled and would playback normally.

Partial recovery of the third podcast audio file

In the radio show, you can hear how the producer tried to "Wake up" the SD card by copying some additional data to the SD card after the data loss. The golden rule of data loss/recovery applies here: if you lose data turn the device off and do not attempt to use it. The audio recordings they wished to recover had not been marked as 'allocated' within the FAT. Consequently, when new data was copied to the SD card it wrote to areas of the SD card which contained the required data. Once data has been overwritten with new data there is no method to reverse this. As a consequence, it was only possible to recover the first 15 minutes of audio associated with the third podcast recording.

Until February 2021 you can listen to the full BBC Radio 5 Live Elis James and John Robins episode from the BBC's website.

Data Recovery Case Studies
Too good to be true data recovery
Stephen Owens
Stephen Owens
12:42 14 Mar 24
After a catastrophic HDD failure, I was shocked to find that my Mac’s Time Machine had excluded (apparently by default because it wasn’t an internal drive?) the drive from my backups. I then... discovered I’d lost 52 years worth of photographs, many of which were irreplaceable.I contacted John after checking reviews of various data recovery companies and after discussing things with John, entrusted him with the recovery. John was very clear up front about costs and chances of recovery - given the specific type of Seagate drive involved - and then set about recovering the data.First efforts were largely successful after reading as far as the disk errors but after I was thinking that was it, John suggested he could made a second attempt - reading backwards to the errors - which indeed proved additionally successful. Results were:* Photo’s in library:  21,745* Photo’s unrecovered: 450* Unrecovered photo’s replaceable: 448* Unrecoverable photo’s lost: 1 (possibly 2)…which equates to a 99.99% success rate!I’ve undoubtedly not recovered other files but it was the photo’s (and memories) that are crucially important and I only have the highest recommendation for the efforts that John put in over and above what could be expected in recovering them.I’m hoping I never have such a situation again but if I do, I know where to come to for help.Many thanks, JohnKind regards,Stephen Owensread more
Yvonne Ledden
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John is a first class data analyst, who offers a pristine and premium service, from the very outset of your enquiry to the completion of the data recovery project. I would not hestitate to highly... recommend John, and, had I not been fortunate enough to live quite local, I would be willing to travel a considerable distance to use his unbeatable data skills. He doesn't have the letters, and 'Dr'., before his name for nothing! I am eternally grateful to him for recovering 4 TB of irreplaceable data for me.Thank you so much John,Kindest regards from,Yvonne Ledden.read more
Terry Abrahams
Terry Abrahams
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CDR did a great job of recovering files from one of my 1TB HDDs. Despite a broken R/W head CDR recovered 99% of the files on the broken drive and within the timescale quoted. I would highly recommend... CDR for data recovery on HDDs.read more
iron mike
iron mike
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