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2010/02/26 Higher Altitude GoPro HD Flights at Rancho San Antonio and Motor Failure, and Video recovery from SD Card
π 2010-02-26 00:00 in Rc
After adding a tail ribbon to my plane (to make it easier to see where is the front and back when it's far away from me), I went for a few more flights to catch some higher altitude HD video.

My first flight went mostly ok: (make sure to select HD in the resolution slider)

Unfortunately, on the second flight, the motor crapped out. First it started vibrating a lot, hence the shaky video, and when I removed the throtlle in flight when preparing for landing, I wasn't able to re-engage it. The video after the fact gives the 4 beep code from the ESC which means motor failure, shutting down. At that point, the minimag with all that weight feels like a 2 for 1 glider at best. I don't remember if I tried to flare, but it looks like I barely had enough lift glide energy left to make it to the edge of the hill (beyond that, it would have gone below my field of view)
Turns out I was able to restart the motor on the ground after a full shutdown, but it didn't restart in flight and you can hear the unhappy motor sounds :)

Just like motor, the video had a problem: after downloading it on my laptop, I screwed up while recompressing the first video and wiped the second video in the process. The second video was still on the sd card, but its cluster table had been freed since I had reused the card already.
In this case, photo recovery software usually only has to find the signature of the file by scanning blocks, read the file header and deduce how long the file is from that info since it's already lost in the cluster table, and then rely on the fact that all blocks are super likely to be contiguous, so you can just keep reading linearly until you have the whole file. This usually worked well, but Christophe GRENIER's very handy photorec wasn't succeeding there, and neither were other pieces of commercial software I tried: the restored file would not play (I restored the file by hand myself too by just copying the blocks and got the same result).
In the end, I got really good help on the mencoder-users list from Reimar Döffinger, whom I owe a debt of gratitude to: he looked at my sd card image and figured out that my GoPro HD Camera wrote the index-related part of the file header, after the data blocks. With Reimar's help on what offsets I should be looking at, I was able to get the first part of the header at the beginning, concatenate the end of the header that was written after the data blocks, and then add the actual data blocks. After almost 2 weeks of trying, his answer worked and I got my file back. If you are interested in more details, see this message from the mencoder-users list.

Here it is: (make sure to select HD in the resolution slider). Jump to 04:20 for the motor failure.

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