How to Recover Dash Cam Footage That Won't Play

13 June 2019 | by the restore.media team

Every month we get a number of requests to recover dash cam footage. And just recently, we've got the following feedback from one of our clients:

"We had a bad car accident and the video was not viewable when copied from the SD card. It was critical to recover the video from the dash camera so the insurance company could determine we were not at fault.

I have basic recovery skills, I tried all the free tools and even other websites. Restore.Media had clear instruction on how to get them the data from the SD card and they recovered the video! I wish I knew to just start with Restore.Media, now I do. The cost was reasonable and communication with the staff was superb. Thank you!"

- Dan F

In this article, we'd like to share why video files recorded on a dashboard camera may get damaged during a car accident and how to recover dash cam footage, so that you can use it as evidence in case of insurance claims or disputes in court.

Recover Dash Cam Footage

So, here we go…

Why You Can't Play Car Accident Video Shot on Your Dash Cam

Your dash cam may work just fine for months or years with no issues. Oddly, though, when an accident actually happens and you need to pull out those important few seconds of the footage, it appears that the video is corrupted and won't play back.

You may have working video files recorded just before the accident. You may also have videos recorded after the accident had happened. But the actual crash is missing, or the video is damaged.

Why?

Apart from actual video and audio streams, most of the popular video file types, like MP4 and MOV, also include metadata and indices. Metadata contains details about video frame rate, resolution, bit rate and codecs used to encode the video. Both metadata and indices are needed for media players to play the video.

When recording, dash cams write video and audio streams to the memory card on the fly. But the metadata and indices are kept in camera's internal memory and are usually saved at the end of the video file.

If a car accident happens, your dashboard camera may lose power due to a number of reasons. For example, some cars cut off power supply intentionally when the vehicle is in a collision.

Now, comes the problem #1 – if your dash cam's internal battery doesn't have enough power, it may fail to save the metadata along with indices into the final video file.

The problem #2 arises because of how the file system works. When writing video on a memory card, the file system allocates free clusters to save the video. Once the data is written, the file system marks clusters occupied by the video in its file allocation table.

However, if an accident happens and the camera loses power, the file system may fail to mark the clusters occupied by the last few seconds of the video. When you turn on your dash cam again, the file system will recognize those clusters as if it was free space, even though they contain the most important chunk of the accident's video.

SD Card Memory Clusters

Recovering Dash Cam Videos that Won't Play

First, we strongly suggest taking the SD card out of your dash cam as soon as possible before the camera is powered back on after the accident. Otherwise, the camera may overwrite the last few seconds of the video with new data.

To ensure the memory card is not altered in any way, it is also a good idea to put the card in a full-size SD adapter and then lock it to a read-only mode with the help of the switch on the left-hand side of the adapter.

Now, you need to create a backup image of the SD card. This must be an exact byte-by-byte image of the entire memory card. The image type must be no other than ".IMG". This type of image files includes data from all clusters of the SD card, including those that the file system mistakenly marked as "free space". So, if you have a 64GB memory card, then the image file would be exactly 64GB. Having such an image file may be the only source to recover the last few seconds of the road accident footage.

To create an image file, Windows users can use a free USB Image Tool. MacOS users need to follow instructions from this page. Please note that neither .ISO, nor .DMG image types won't work as they don't contain data from free space clusters. Again, the image type must be ".IMG".

Having the image file, you can now try to recover the corrupted video file. For this, create a free account at Restore.Media and then follow the instructions.

You will be asked to specify your camera model and then upload a reference video. This might be any valid (playable) video file shot on your dash cam, just before the accident happened.

Based on your specified camera and settings, Restore.Media will choose the optimal recovery algorithm. The tool supports dash cams of all popular vendors, like Novatek, Xiaomi, BlackVue, Street Guardian, Mio MiVue, Vicovation, Ricoh Theta, Street Storm and others.

Depending on the file size, it may take several minutes to recover your dash cam footage. Essentially, on this stage Restore.Media can fix the problem #1 described earlier. It re-creates the missing metadata and indices in the corrupted video file, so that it can be played in media players.

When the process is completed, the tool will provide you with a full-time preview of the recovered video file. Please note that the video in the preview is in low resolution and bit rate. To get the file in the original resolution, you need to download it. But before doing so, we encourage you to preview the last minute of the video to make sure the file is fully recovered.

If you don't see the last few seconds of the accident, then your image file must be processed manually to recover missing data from the free space clusters (problem #2).

For this, you could upload the image of your SD card to a file sharing service, like Google Drive, and email us a link along with a short description of the issue. One of our engineers will personally review the image and let you know if the video can actually be recovered.

Back to the client's feedback given earlier. The owner's camera failed to finalize the video properly. Once the metadata and indices were fixed, it appeared that the footage still misses the last few seconds, which is the most important part of the video. Luckily though, the clusters with the missing video chunk remained untouched and we managed to recover these few seconds of the video after the client provided us with the image of the SD card. Also, here is a short video that explains in detail how all this stuff works:


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If you're in a similar situation and need to recover dash cam footage, please feel free to contact us – our engineers will do their best to help you. Be safe and happy recording!