Letsrobot.tv / Run My Robot Overlay Guide

Both of these methods expect a PNG image with transparency to be the same size as your video feed ( 640x480 by default ). It is possible to blend images at different resolutions with alternate commands but beyond the scope of this document.

Static video overlay

Requires no modification to FFMPEG
Add overlayCommand and change the videoCommandLine in send_video.py:

staticOverlayCommand = '-f image2 -i /home/pi/runmyrobot/images/hud.png -filter_complex "[0:v]format=argb,geq=r=\'r(X,Y)\':g=\'g(X,Y)\':b=\'b(X,Y)\':a=\'0.7*alpha(X,Y)\'[overlay]; [1:v][overlay]overlay"'

videoCommandLine = '/usr/local/bin/ffmpeg {overlay} -f v4l2 -framerate 25 -video_size 640x480 -i /dev/video{video_device_number} {rotation_option} -f mpegts -codec:v mpeg1video -s {xres}x{yres} -b:v {kbps}k -bf 0 -muxdelay 0.001 http://{server}:{video_port}/hello/{xres}/{yres}/'.format(overlay=staticOverlayCommand,video_device_number=commandArgs.video_device_number, rotation_option=rotationOption(), kbps=commandArgs.kbps, server=server, video_port=videoPort, xres=commandArgs.xres, yres=commandArgs.yres)

Dynamic video overlay ( polls filesystem for modified file at specified interval, default 2Hz )

Requires additional code to be compiled with FFMPEG ( see below )
Add overlayCommand and change the videoCommandLine in send_video.py:

overlayCommand = '-vf dynoverlay=overlayfile=/home/pi/runmyrobot/images/hud.png:check_interval=500'

videoCommandLine = '/usr/local/bin/ffmpeg -f v4l2 -framerate 25 -video_size 640x480 -i /dev/video%s %s -f mpegts -codec:v mpeg1video -s 640x480 -b:v %dk -bf 0 -muxdelay 0.001 %s http://%s:%s/hello/640/480/' % ( deviceAnswer, rotationOption, args.kbps, overlayCommand, server, videoPort)

To compile FFMPEG with Dynoverlay filter use these modified instructions from step 6 in the README

sudo apt install gnutls-dev

cd /usr/local/src

git clone https://github.com/r3n33/FFmpeg.git -b dynoverlay

cd FFmpeg

./configure --arch=armel --target-os=linux --enable-gpl --enable-libx264 --enable-nonfree --enable-gnutls --extra-libs=-ldl --enable-zlib

make -j4

sudo make install

UPDATE: Dynoverlay now supports multiple overlays and X,Y offsets. (Images can be small and placed in various locations.)

For example:

overlayCommand = '-vf dynoverlay=overlayfile=/dev/shm/battery.png:check_interval=1000:x=520:y=383,dynoverlay=overlayfile=/dev/shm/nametag.png:check_interval=5000:x=0:y=395'

UPDATE 2: Best location for dynoverlay parameters

In the python send_video.py you can add the video filter parameters to the empty return string if you are not flipping your video 180 degrees. If you are rotating your video append the dynoverlay information after the last transpose=2. For example:

def rotationOption():

    if commandArgs.rotate180:
        return "-vf transpose=2,transpose=2"
    else:
        return ""

to this:

def rotationOption():

    if commandArgs.rotate180:
        return "-vf transpose=2,transpose=2,dynoverlay=overlayfile=/dev/shm/battery.png:check_interval=1000:x=520:y=383,dynoverlay=overlayfile=/dev/shm/nametag.png:check_interval=5000:x=0:y=395'"
    else:
        return "-vf dynoverlay=overlayfile=/dev/shm/battery.png:check_interval=1000:x=520:y=383,dynoverlay=overlayfile=/dev/shm/nametag.png:check_interval=5000:x=0:y=395'"