Re: Python and webcam capture delay?

Tim Roberts kirjoitti:
"jack catcher (nick)" <nomail@xxxxxxxxx> wrote:
I'm thinking of using Python for capturing and showing live webcam stream simultaneously between two computers via local area network. Operating system is Windows. I'm going to begin with VideoCapture extension, no ideas about other implementation yet. Do you have any suggestions on how short delay I should hope to achieve in showing the video? This would be part of a psychological experiment, so I would need to deliver the video stream with a reasonable delay (say, below 100ms).

You need to do the math on this. Remember that a full 640x480 RGB stream
at 30 frames per second runs 28 megabytes per second. That's more than
twice what a 100 megabit network can pump.

You can probably use Python to oversee this, but you might want to consider
using lower-level code to control the actual hardware. If you are
targeting Windows, for example, you could write a DirectShow graph to pump
into a renderer that transmits out to a network, then another graph to
receive from the network and display it.

You can manage the network latency by adding a delays in the local graph.

Thanks Tim, you're correct about the math. What is your main point about DirectShow: that it is generally faster and more reliable than doing the job high-level, or that one could use coding/decoding in DirectShow to speed up the transmission? I think the latter would be a great idea if the latency were tolerable. On the other hand, I'd like to keep things simple and do all the programming in Python. I've got no experience with DirectShow, but I guess the filters need to be programmed in C++ and called from Python?

Another option might be to use resolution 320x240@15fps.
.

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