Entropy looks good but repair is unsuccessful?
Note that good entropy does not mean by definition JPEG. You may get similar entropy when the file is filled with other compressed data. However there a few things you can try (and that worked for me in the past sometimes):
- Run Extract JPEG option on JPEGs. I have had success using this method getting full and partial (but still usable) images from incorrectly recovered photos. Procedure is the same as for extracting JPEG from RAW (see above video).
- Use Patch + Append option. This requires a sample or reference file that was shot with the same camera and settings (such as quality).
If extracting JPEG from the corrupted files yields no results then the file contains no complete JPEG file(s). However, since entropy is good there is still a chance there is encoded JPEG data within the file that can be reconstructed. To find out you have to examine the files one by one (no batch).
This is often required to repair incorrectly recovered photos: the undeleter or file recovery tool mixed a partial image with other data that was present on the medium the data is recovered from.
Advanced repairs using JPEG-Repair Toolkit
This is an advanced repair that requires manual input. You will also need a sample / reference file. A sample file is an intact JPEG shot with the same camera using the same settings. You need to rename the reference file to sample.jpg and place it in the same folder as the file you want to repair.
Carve JPEG data from file and append valid JPEG header
- Double click “jpgrepair.exe”. There is no setup, just a single executable file.
- Select Patch and enable the ‘append’ checkbox.
- Browse to the folder containing the corrupted photos + reference file (that is named ‘sample.jpg’ without quotation marks).
- Select the corrupt file you need to repair.
- Click “Repair”. It is very likely that JPEG-Repair will prompt you to load a file it has made modifications to. It may take several iterations to get it right. Just keep following the messages JPEG-Repair displays. It may prompt to load files several times.
- It is likely the image is severely distorted. You will need to remove obvious corrupted data until a recognizable image is achieved.
Note: Append with be un-checked as you only need to append the header of the donor file once. Leave unchecked!
- It is very likely the resulting image will need further processing using a photo editor.
- It is strongly advised to watch following video that will show you what to expect: