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Created February 12, 2015 02:48
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An example command to grab images from a webcam.
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example_command.md

Example Command

This is the example command that will take pictures periodically:

$ ffmpeg -f v4l2 -i {{device, e.g. /dev/video1}} -ss 0:0:2 -s 120x90 -vsync 2 -r 4 -updatefirst 1 stream.png

  • -f v4l2 uses the standard linux /dev/video decoder thing.

  • -i {{device}} uses the given {{device}} as the input device.

  • -ss 0:0:2 streams the webcam for 2 seconds prior to starting the stream. This will enable the webcam to warm up; in the case of the RZ406AA, there is a 2-second warmup period in which the R and B channels must be slowly brought up for some stpid reason.

  • -s 120x90 sets the output size. This can be changed according to the whims of the programmers.

  • -vsync 2 synchronizes the output buffer (removes some bulky watchdogs) and drastically decreases CPU utilization.

  • -r 4 specifies the rate at which the output is updated.

  • -updatefirst 1 and stream.png are used for a singular-file streaming setup. FFMpeg will update the file as it reads new image data from the webcam. Alternatively, one can use stream%5d.png to write out to enumerated files, and then can programmatically determine the latest file, but this consumes more space and is silly.

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