Visualize the motion vectors in an h264 encoded video using ffmpeg and vlc (works on OSX)

vis_motion_vectors.sh

vis_motion_vectors ()
{
    if [ "$#" -lt 1 ]; then
        echo "Need an input file";
        return 1;
    else
        ffmpeg -y -loglevel error -flags2 +export_mvs -i "$1" -vf codecview=mv=pf+bf+bb /tmp/motion_vectors.mp4;
        case "$(uname -s)" in
            Linux*)  vlc /tmp/motion_vectors.mp4;;
            Darwin*) open /tmp/motion_vectors.mp4 -a vlc;;
            *) echo "unknown platform, unable to run. open /tmp/motion_vectors.mp4 in VLC manually";;
        esac
    fi
}


# use like 
# $ use_motion_vectors /tmp/video.mp4
# it will open VLC with a new video that has the motion vectors encoded over the video