The corruption might have been occurred due to following reasons:
1) Deleted photos were overwritten by new files before running the photo recovery software.
2) Bad sectors may also corrupt the photos or allows partial recovery of photos.
This tool allows batch repair of corrupt/damaged JPEG and JPG files.
Here is a demonstrational video how the software operates.
In case you need to contact the support team of Stellar Phoenix, please find good contact details here.