Decoding freeGPS data from video

[carvideo]

I want to extract GPS data from my video that I recorded with a dashcam of the brand "EEEkit".

The video seems to have timestamped GPS and accelerometer data in it, as this is what I see when the video is replayed.

To extract the GPS data, I use the following command:

./exiftool -ee -V3 -n ../vid1_front.mp4 > test.txt

It looks like the data is extracted, but unfortunately I am unable to convert the data into lon/lat, timestamps, etc, which is what I assume is in the data.

Here is some sample data (full file attached):

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Type='gps ', Sample 107 of 180 (1024 bytes)
8509f30: 00 00 04 00 66 72 65 65 47 50 53 20 f0 03 00 00 [....freeGPS ....]
8509f40: 01 03 aa aa f2 e1 f0 ee 54 54 98 9a 98 9a 9a 9f [........TT......]
8509f50: 9b 99 9b 9c 99 9f 9e 9b a6 9a 9a 98 9a 9a 9f 9b [................]
8509f60: 99 9b 9c 99 9f 9e 9b a9 e4 99 9d 9e 9f 9a 9f 9a [................]
8509f70: 98 fd 9b 98 98 98 9f 9d 99 98 9e 81 9a 9a 99 9e [................]
    [snip 944 bytes]
Type='gps ', Sample 108 of 180 (1024 bytes)
863e614: 00 00 04 00 66 72 65 65 47 50 53 20 f0 03 00 00 [....freeGPS ....]
863e624: 01 03 aa aa f2 e1 f0 ee 54 54 98 9a 98 9a 9a 9f [........TT......]
863e634: 9b 99 9b 9c 99 9f 9e 98 a6 9a 9a 98 9a 9a 9f 9b [................]
863e644: 99 9b 9c 99 9f 9e 98 a9 e4 99 9d 9e 9f 9a 9e 93 [................]
863e654: 92 fd 9b 98 98 98 9f 9d 99 9d 99 81 9a 9a 99 9e [................]
    [snip 944 bytes]
Type='gps ', Sample 109 of 180 (1024 bytes)
878c374: 00 00 04 00 66 72 65 65 47 50 53 20 f0 03 00 00 [....freeGPS ....]
878c384: 01 03 aa aa f2 e1 f0 ee 54 54 98 9a 98 9a 9a 9f [........TT......]
878c394: 9b 99 9b 9c 99 9f 9e 99 a6 9a 9a 98 9a 9a 9f 9b [................]
878c3a4: 99 9b 9c 99 9f 9e 99 a9 e4 99 9d 9e 9f 9a 9e 93 [................]
878c3b4: 99 fd 9b 98 98 98 9f 9d 9e 9b 98 81 9a 9a 99 9e [................]

Do you have any tips how I could decode this data properly?

[StarGeek]

Did you try just
exiftool -ee -gps* ../vid1_front.mp4 > test.txt
to see if exiftool decodes it properly already?

[carvideo]

This command just returns an empty response. Any other ideas how to resolve this?

[StarGeek]

Can you make a short moving (not staying in one place) sample available?

[Phil Harvey]

This looks like another variant of the encrypted freeGPS format.  Email me a sample and I'll add support for this (philharvey66 at gmail.com)

- Phil

[carvideo]

Here is a small example video:

https://drive.google.com/file/d/1FusBUbfoC19mQ_0FVJwogizVV5-SNgza/view?usp=sharing

[Phil Harvey]

I got it.  I'll let you know after I have had a chance to analyze it (give me a few days).

- Phil

[Phil Harvey]

Great.  I can decode the GPS from this sample.  ExifTool 12.00 will have this ability.

This makes 41 different types of streaming GPS that ExifTool can decode.

- Phil

[carvideo]

Excellent, will the 12.0 automatically detect this format? so I can just run:

Code Select Expand

exiftool -ee -gps* video.mp4 > video.gpx

Can't wait to test it. 41, that's unbelieveable! Thanks so much!

[Phil Harvey]

Excellent, will the 12.0 automatically detect this format? so I can just run:

Code Select Expand

exiftool -ee -gps* video.mp4 > video.gpx

The command would be

exiftool -p gpx.fmt -ee video.mp4 > video.gpx

with this gpx.fmt file.

- Phil