user25329: I have a MP4 File which has not been finalized at the end so there is no header. The file contains 3 streams: 2 video streams and 1 audio stream.
I tried several tools to repair the header but the best I get is a video where the 2 video streams alternate after about 2 seconds (2 seconds first video, then 2 seconds second video, 2 seconds first video and so on). I also have a working reference file but the header is still not correctly repaired with those tools.
Here are the tools I tested:

Some freeware like Yodot MOV Repair 
Yamb (file could not be loaded)
recover_mp4 / recover_mp4_to_h264 (the two video streams will be
extracted as one video stream)

I don't think it was from a GoPro. It was from a Race Keeper System with one front facing camera and a second one filming the people in the car seats. So there are 2 different streams with HD quality. I don't even need both streams, one of them would be enough if that helps.
Maybe it is still possible with one of that tools but I could not figure it out.
I would really appreciate some help.

user25330: Have you recorded the video with a GoPro camera?
If yes, then the two video streams may be a low-res preview video followed by the regular video stream. To repair such file, you would have to filter out the low-res stream.
So far as I know, the new version of the recover_mp4 has an algorithm of filtering out low-res streams of the GoPro cameras. The tool is now called Restore.Media. You can try repairing your MP4 with this tool and watch a full-time preview for free just to see if it works. Also, here is their article about repairing GoPro video files.   

25329: <p>I have a MP4 File which has not been finalized at the end so there is no header. The file contains 3 streams: 2 video streams and 1 audio stream.</p>

<p>I tried several tools to repair the header but the best I get is a video where the 2 video streams alternate after about 2 seconds (2 seconds first video, then 2 seconds second video, 2 seconds first video and so on). I also have a working reference file but the header is still not correctly repaired with those tools.</p>

<p>Here are the tools I tested:</p>

<ul>
<li>Some freeware like Yodot MOV Repair </li>
<li>Yamb (file could not be loaded)</li>
<li>recover_mp4 / recover_mp4_to_h264 (the two video streams will be
extracted as one video stream)</li>
</ul>

<p>I don't think it was from a GoPro. It was from a Race Keeper System with one front facing camera and a second one filming the people in the car seats. So there are 2 different streams with HD quality. I don't even need both streams, one of them would be enough if that helps.</p>

<p>Maybe it is still possible with one of that tools but I could not figure it out.</p>

<p>I would really appreciate some help.</p>
 25330: <p>Have you recorded the video with a GoPro camera?</p>

<p>If yes, then the two video streams may be a low-res preview video followed by the regular video stream. To repair such file, you would have to filter out the low-res stream.</p>

<p>So far as I know, the new version of the recover_mp4 has an algorithm of filtering out low-res streams of the GoPro cameras. The tool is now called Restore.Media. You can try repairing your MP4 with this tool and watch a full-time preview for free just to see if it works. Also, here is <a href="https://restore.media/blog/how-to-repair-corrupted-gopro-video-files" rel="nofollow noreferrer">their article</a> about repairing GoPro video files.   </p>
