Low Latency Video Streaming

Due to the COVID-19 madness in Germany I was forced to perform all my penetration testing remotely. This is quite challenging when you have to make sure that devices can be powercycled reliably. Additionally, the power consumption is often an indicator for a crash. Having on overview of the current consumption of my setup makes perfect sense.

The powercycle problem was trivial. I grabbed a R&S power supply which offers a programming interface. A few lines of python and I'm done. Hint: Use the raw tcp port 5025, it is a very simple ASCII line based protocol. Even telnet can be used to remote control the device.

The challanging thing was video. During my testing I need visual feedback for what I am doing, i.e. “hit enter, look at the power consumption. Anything changed?”. A video of the power supply display would be nice… I had set up a cheap Logitech webcam in order to stream the video over the network (through VPN and who knows…). The problem was… 30 sec delay. Unusable.

After a lot of tinkering, I found out these settings:

On the server:

$ cvlc v4l2:// :v4l2-vdev="/dev/video0" --sout '#transcode{vcodec=h264,venc=x264{preset=ultrafast,tune=zerolatency,intra-refresh,lookahead=10,keyint=15},scale=auto,ab=128}:std{access=http{mime=video/x-ms-wmv},dst=:8082/stream.wmv}' -v --no-sout-audio

On the client:

$ mpv --profile=low-latency --stream-lavf-o=reconnect_streamed=1 HOST:8082/stream.wmv

I works quite well. Due to the massive amount of profiles and settings (and not being a video pro) I simply got lost. Hope this help.