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Recently I've been working on a project to stream video from one raspberry pi zero with a camera module to another with a small TFT display. The application demands that this stream has very, very little latency. I've been able to achieve the goal of streaming video using this github code:

https://github.com/miguelgrinberg/flask-video-streaming.git

I need a solution that utilizes internet protocols. This ensures the two computers could be across the world from each other and still function at a high level. This solution attains that goal, However, this system has far too much latency and can only provide about twenty frames per second. Is this a result of the pi zero's 2.4 ghz anteanna? Is this a limitation of Motion JPEG systems? Any suggestions to decrease latency in the video stream would be appreciated.

  • Much of the time, video streaming latency is down to the client buffering frames (because most video playback systems are optimized for streaming pre-recorded stuff and assume that buffering a second or two's worth of video is sensible to guard against network drop-outs). That's the first thing I'd check. – Dave Jones Jun 18 '17 at 18:39
  • What would the solution to that problem be? – Roark Piacente Jun 19 '17 at 21:21
  • Depends entirely on the client and whether you can persuade or configure it to forgo buffering frames – Dave Jones Jun 19 '17 at 21:56
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You need first to analyse your system to detect the bottlenecks :

Using top command, you will see how much CPU and RAM are used.

To analyse network usage, you can measure it from the rapsberry (using i.e. vnstat ) or from the client side, and compare it to your WIFI estimated bandwith (802.11b = 2-3 Mbps / 802.11a and 802.11g = ~20 Mbps).

In one of these limits are reached, your only options are to decrease image resolution, to move your project to a stronger Rpi, or maybe to optimize the code you use (or it's context).

You may also want to give a try to the program named uv4l, that easily implement camera control and webRTC streaming, in a quite efficient way. https://www.linux-projects.org/uv4l/

  • The CPU usage was at maximum 45% for the python program and 88% maximum for the whole system. I don't think the issue is video resolution either, I'm only streaming at 320 pixels by 240 pixels. I tested the network, it's either 802.11a or 802.11g and came in at 5.50 mbps download and 11.7 mbps upload. If that's limiting the frame rate I could use a a phone hotspot that I tested at 7.40 mbps download and 1.05 mbps upload. Would that work better or worse than the current network? – Roark Piacente Jun 19 '17 at 15:38
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    I checked out uv4l, works great at 60 fps! Thanks for the help. – Roark Piacente Jun 20 '17 at 1:16

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