OpenCV FFMPEG mp4 codec error

[LemonPi]

Recording videos is having trouble using the mp4 format, with the fallback producing gigantic video sizes (~200MB for a 1 minute video). This is with the latest master (3a3d1dea020843704e0a4cf89433e8275d614437).

[rosout]: Starting recording for /home/victorrope/catkin_ws/src/arm_video_recorder/Captures/1601573755.8293712.mp4
OpenCV: FFMPEG: tag 0x7634706d/'mp4v' is not supported with codec id 13 and format 'mp4 / MP4 (MPEG-4 Part 14)'
OpenCV: FFMPEG: fallback to use tag 0x00000020/' ???'

(also tried with different filenames such as "video.mp4")

[LemonPi]

ffmpeg is not installed separately on this machine; will try again after installing ffmpeg

[LemonPi]

Separately installing ffmpeg version 2.8.17-0ubuntu0.1 did not change this problem (after catkin_make and resourcing).
Running opencv_version returns 3.3.1-dev

[bsaund]

Here is where the fourcc code is set. You could ty changing that.
https://github.com/UM-ARM-Lab/arm_video_recorder/blob/master/scripts/video_recording.py#L38

Separately, isn't victorrope the virtual machine? You may encounter additional challenges when trying to record inside the VM

[LemonPi]

Good point, running the service on the host machine without changing anything else does not raise this issue. That can be the solution for now; I will play around a bit with the code inside the VM to see if that can also be resolved.

A separate issue is the size of the videos. I'm still getting around 200MB for a 1 minute mp4, even without any codec issues. I remember the mp4 format being much more compact?

Update: changing the FourCC code cannot solve the problem inside the VM (could be a cv2 version issue).