Taking apart a .360 file to reveal its contents to try and understand how it can be processed (without GoPro software).
This week I’ll use a video I shot on a Trek Pack v2 (GoPro Max) to try and understand how to work with .360’s in practice.
Here’s a GoPro video shot at 6K / 30 FPS on the MAX camera.
It was uploaded to YouTube after being converted from .360 to .mp4 (EAC to equirectangular projection) in GoPro Studio.
I can extract a frames from this .mp4 video with ffmpeg by following the instruction in my post; Turning a 360 Video into Timelapse Images.
For this example, I’ll use 1 frame every second:
$ ffmpeg -i GS070135.mp4 -r 1 -q:v 2 MP4-FRAMES/img%d.jpg
Above is the first frame (reduced in resolution for this post, original = 4096x2048) from the extraction,
Now going back a step, let’s look at the original .360 file (download it here).
Looking at the metadata from the .360 file:
$ exiftool -ee -G3 -api LargeFileSupport=1 -X GS070135.360 > GS070135-360.txt
Although it’s a .360 file format, GoPro actually declare it as an .mp4:
<File:FileType>MP4</File:FileType> <File:FileTypeExtension>mp4</File:FileTypeExtension> <File:MIMEType>video/mp4</File:MIMEType>
We know from last weeks post, there are two video tracks in the file (you can also see this in the exif):
<Track1:HandlerDescription>GoPro H.265</Track1:HandlerDescription> <Track6:HandlerDescription>GoPro H.265</Track6:HandlerDescription>
Thus, running the ffmpeg command used before, e.g.
$ ffmpeg -i GS070135.360 -r 1 -q:v 2 FRAMES/img%d.jpg
Would run, but would only extract one track.
This command only looks for a single video track to extract (as mp4’s typically contain a single video track).
Therefore we need to explictly define the tracks for extraction. In the case of .360’s this is track 0 and 5:
$ ffmpeg -i GS070135.360 -map 0:0 -r 1 -q:v 2 track0/img%d.jpg -map 0:5 -r 1 -q:v 2 track5/img%d.jpg
Note, this extracts at 1 FPS (
-r 1). ffmpeg counts from 0, so Track1 in exiftool output is Track0 in ffmpeg.
You can also copy the video file from each track, if needed:
$ ffmpeg -i GS070135.360 -map 0:0 -vcodec copy -acodec copy track0.mp4 -map 0:5 -vcodec copy -acodec copy track5.mp4
Above is the first frame (reduced in resolution for this post, originals = 4096x1344) for each track of the extraction,
Above are the two images in one track (0 at top, 5 at bottom). I have also added a grid to display each cube annotated with its direction and rotation.
You can create a video file of the two track jpgs in ffmpeg to get this frame like so:
$ ffmpeg -i GS070135.360 -filter_complex "[0:0]pad=4096:2688[put],[put][0:5]overlay=x=0:y=1344" GS070135-eac.mp4
But really this video is useless. In EAC (or GoPro EAC) projection, other software won’t be able to read it. It needs to be converted to equirectangular.
Update 2021-09-24: Part 3 now available
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