This happens in parallel, with interpretations of the same data segments on the disk being interpreted and displayed as different files, and this can occur thousands of times per second. Multiple file outputs for the same data segment on the disk is necessary to have to get good results, because often files will be embedded inside each other, with each interpretation of the data as a file being equally valid, but distinct. (For example, jpegs embedded windows 7 cost inside a PDF will be offered as individual jpegs, but that will not interfere with the PDF also being displayed and recoverable as a file itself, with the embedded jpegs included.)
While the premise of this form of file recovery is simple and making a prototype is easy, outputting good results from such a chaotic environment is when it becomes a science and an art form and require years of refinement and development. No less than 6 years of full-time research and development has been put into Mac Data Recovery Guru. And that’s not moving slowly.
In this paradigm of data recovery each file is its own universe. Some files such as jpegs have a beginning, a middle and an end. This is quite a simple file type in that sense. Others are very different. An MP3 for example, is a nebulous entity. While scanning through the bytes on a disk, MP3 frames can be found wholly or partly anywhere on a disk, and if you’re the file recovery program it can be hard to know whether you are within an MP3 or not. But it’s the file recovery software’s job to find the fragments, determine if they are clumped together as a single sound file or multiple, and even parse out the ID3 information in order to correctly preserve it so that the album artwork and song name are correctly displayed after the files are recovered. If you try the software you will see that somehow it does this, and remarkably, does so perfectly.
The most challenging aspect of this approach is that the names that the files were arbitrarily named on the filesystem photo recovery tools are often lost, because that is stored in the filesystem itself. We do our best to overcome this limitation by displaying live thumbnail previews of all the deleted files (not an easy feat!), and allowing quick recovery of entire file types in order to later search through them with the OS X Finder and Spotlight.
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