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.

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Paul Ledsham
2 weeks ago
John from CDR Restore Office recovered data from our corrupted SSD drive using their emergency service. We had our data back within just 24 hours! The service was fast, professional, and reliable throughout. We’re extremely grateful and would highly recommend John and CDR Restore Office to anyone needing urgent data recovery.
Response from the owner:Hello Paul, thank you for the review. Your 2TB Cricial SSD (CT2000BX500SSD1) had an electronic failure. A number of capacitors and power management IC had failed. Fortunately donor parts were in stock, and it was possible to resolve the failure of the SSD and make a full recovery in under 24 hours. I remember during your enquiry you asked whether the technical work actually took place by CDR, as you had approached a company which advertised data recovery services, only to find out that they sub-contracted the work. The SSD would have been sent away, leading to extended lead times. This is very common, In Manchester city centre alone there are a number of 'virtual offices' for data recovery companies where no staff are present and your disk would be sent off to an unknown location. I am glad it was possible to make a successful recovery of the data. Best regards, John C. Reid.
Greg Evans
2 weeks ago
Absolutely over the moon with CDR's express service. Two disks failed on a three disk Raid5, with the third hanging on. 5tb of irreplaceable data recovered in a few days. Both myself and our marketing team can't thank you enough. I really hope we don't need your services again, but we're mightily glad that you're there, if we do.
Response from the owner:Hello Greg, thank you for the review. The 3 x 6TB RAID-5 array had failed with two disks suffering from bad sectors. This aspect of the recovery was relatively straight forward to deal with with the appropriate hardware disk imaging equipment. Where this job proved to be more complex, was that one of the disk has been reinitialised, resulting in a different partition structure to the two remaining. This included the starting LBA position of the main partition (LBA 3145728 versus LBA 2120584). The disks came from a QNAP device, which used thin-provisioning. There was corruption of the thin-provisioning metadata database. As a result of both issues above, it was necessary to establish and manually set out the parameters of the RAID array rather than use an automatic rebuild from the associated RAID configuration metadata. By doing so, it was possible to rebuild the thing-provisioning database without error, and rebuild the full folder and file name structure. From this it was possible to achieve a successful recovery of the data. All done so within a 48 hour working time. Best regards, John C. Reid.
Tom Marshall
1 month ago
Stupidly, it was my fault that my HDD failed which then left me trying to find somewhere to get it fixed. From the initial phone call with John through to the end where he managed to recover 99.9% of the files on my HDD. The service was professional and stream lined with good communication throughout and all costs were given to me beforehand so no surprises at the end. So glad I found and chose to use Cheadle Recovery Ltd and recommend his service 100% !
Response from the owner:Hello Tom, thank you for the review, I am glad it was possible to recover the data from your failed Toshiba 1TB hard disk drive. Best regards, John C. Reid.
Events Cheshire Young Carers
1 month ago
Amazing service! John really saved the day by recovering a huge archive of photos spanning many years. The whole process was straightforward from start to finish, and his knowledge and expertise were outstanding. He took the time to talk us through every step, making everything easy to understand and stress-free. We can't thank him enough for helping us recover so many precious memories. Highly recommended!
Response from the owner:Hello Victoria, thank you for the review. I am glad you found the process smooth and clear, and that there was a successful recovery of the data you required. Best regards, John C. Reid.

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