Re: [pygame] Proposed Module: Camera

["René Dudfield" <renesd@xxxxxxxxx>]

hi,

a few notes...

> The basic plan is to use V4L2_MEMORY_MMAP, mmap() the image buffer,
> and convert the image to RGB24 (if it isn't already) as a Surface.

I like that idea.


*- it needs multiple camera support.

So make it create a camera object.

For example:
a_camera = camera.Camera(device, width, height)

a_camera.get_image()

*- you could try implementing your api with the opencv python wrapper.
This way you could start adding tests early on.


*- since many cameras are low frame rate, it would be nice if there
were events emitted for things like FRAME_AVAILABLE.

eg.  if a camera is 10fps then it'd be good if the get image call
didn't block - so then the rest of the program can run faster.

This could require buffering of frames.  Perhaps in a separate thread.
Or maybe there could be a blocking call, and the rest is left up to the user.

What do you think is a good way to handle blocking?

Also I think some cameras require you to get the image data at a
certain frequency... otherwise an internal buffer overflows or
something.  This has been my experience with opencv anyway.


*- Some way to query camera capabilities?





On Tue, May 27, 2008 at 3:22 PM, Nirav Patel <olpc@xxxxxxxxxxxxxx> wrote:
> Hello all,
>
> I'd like to propose a pygame module to enable camera support.
> Specifically, v4l2 support with the eventual possibility of v4l and
> vfw.  I realise having only v4l2 to start with limits it to linux, but
> its a start.  It will consist of the following functions.
>
> camera.open(device, width, height)
> camera.start()
> camera.getimage() returns Surface
> camera.stop()
> camera.close()
>
> The parameters for open are intentionally simple.  Similar to
> libraries like OpenCV, it will negotiate with the v4l2 drivers to pick
> an acceptable pixel format.  At least to start with, the supported
> pixel formats would be the most common ones like RGB3 (RGB24), R444
> (RGB444), YUYV, and others that people want.
>
> The basic plan is to use V4L2_MEMORY_MMAP, mmap() the image buffer,
> and convert the image to RGB24 (if it isn't already) as a Surface.
>
> Nirav Patel
>