DJI Osmo Action 4 GPS information

[kayasaman]

Hi,

I have an Action4 action camera from DJI with the remote controller which provides GPS information which I believe gets embedded into the video file itself rather then using a separate text file to store the data....

At present I have attempted to use the command:

Code Select Expand

exiftool -p /usr/share/perl-image-exiftool/fmt_files/gpx.fmt -ee  -api largefilesupport=1 -ext MP4 -w %f.gpx .
to extract the information into a GPX file.

Unfortunately there seems to be nothing written in the GPX file other then the standard XML markup.

If I add the -V3 option I get much more output:

Code Select Expand

Unknown meta format (dbgi)
Track4 Type='meta' Format='dbgi', Sample 51624 of 51642 (7335 bytes)
4019372eb: 12 a4 39 0a a1 39 0a 0a 10 a1 cd cb b9 05 18 d6 [..9..9..........]
4019372fb: 94 03 12 25 08 35 12 21 4f 56 34 38 43 34 30 5f [...%.5.!OV48C40_]
40193730b: 42 49 4e 32 5f 34 30 33 32 5f 33 30 32 34 5f 35 [BIN2_4032_3024_5]
40193731b: 30 30 30 50 5f 43 50 48 59 1a 28 08 4e 12 24 54 [000P_CPHY.(.N.$T]
40193732b: 50 4c 47 5f 4f 56 34 38 43 34 30 5f 56 49 44 45 [PLG_OV48C40_VIDE]
    [snip 7255 bytes]

which by the looks of it seems like the meta information is not supported?


I am just uploading a sample video file right now to my GDrive and will post it here once ready as it will take some time as it's quite large and will post once ready.


Can anything be done in EXIFTool in order to read the output I wonder?


Many thanks.

[kayasaman]

Here's a sample video:

https://drive.google.com/file/d/10CvcltTMcmF6grNbJYWikVOzC6xCrQac/view?usp=sharing

[kayasaman]

Hi, I wonder if there is any feedback on this?

Is it possible or do I need to use another tool like Telemetry Extractor?

[StarGeek]

This will require Phil's attention. It looks like I tried everything you did and I got the same, empty results.

[Phil Harvey]

I haven't yet seen 'dbgi' information like this, but I'll see what I can do.

- Phil

[Phil Harvey]

I've taken a more in-depth look.  There is unknown timed 'djmd' metadata as well as the unknown 'dbgi', and one tonne of each.  A lot of it looks like telemetry data (accelerations for example), but I haven't been able to find the GPS yet.  This will take some time.  I'll post back here if I discover anything.

What type of information are you able to see in this file using the DJI software?

- Phil

[Phil Harvey]

I've spend a few hours on this now.  I can decode 7 accelerometer readings from the 'djmd' data, but I don't think this decoding is reliable enough to include in ExifTool.  The problem is that they are using variable-length integers in their records, and the byte positions of the data change whenever one of these variable-length values rolls over.  Also, there are many different record types, and all of them require a-priori knowledge of the record length.  So the data cannot be parsed if you don't know the length of one of the records.

I've looked for GPS coordinates, but I seriously doubt that this is written in the video.  I can't see anything that looks like GPS.

If anyone has any detailed information about the 'dbgi' or 'djmd' information, please let me know and I'll see about adding the ability to decode this.

- Phil