[libcamera-devel] [PATCH v2 12/19] py: examples: Add itest.py

[Laurent Pinchart]

Hi Tomi,

Thank you for the patch.

On Tue, May 24, 2022 at 02:46:03PM +0300, Tomi Valkeinen wrote:
> Add a small tool which gives the user an IPython based interactive shell
> with libcamera capturing in the background. Can be used to study and
> test small things with libcamera.

Interesting.

Can I let you update this in a v3 to take comments from other patches
into account, and review it then ?

> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ideasonboard.com>
> ---
>  src/py/examples/itest.py | 197 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 197 insertions(+)
>  create mode 100755 src/py/examples/itest.py
> 
> diff --git a/src/py/examples/itest.py b/src/py/examples/itest.py
> new file mode 100755
> index 00000000..01e020e2
> --- /dev/null
> +++ b/src/py/examples/itest.py
> @@ -0,0 +1,197 @@
> +#!/usr/bin/env python3
> +
> +# SPDX-License-Identifier: BSD-3-Clause
> +# Copyright (C) 2022, Tomi Valkeinen <tomi.valkeinen at ideasonboard.com>
> +
> +# This sets up a single camera, starts a capture loop in a background thread,
> +# and starts an IPython shell which can be used to study and test libcamera.
> +#
> +# Note: This is not an example as such, but more of a developer tool to try
> +# out things.
> +
> +import argparse
> +import IPython
> +import libcamera as libcam
> +import selectors
> +import sys
> +import threading
> +
> +
> +def handle_camera_event(ctx):
> +    cm = ctx['cm']
> +    cam = ctx['cam']
> +
> +    # cm.read_event() will not block here, as we know there is an event to read.
> +    # We have to read the event to clear it.
> +
> +    cm.read_event()
> +
> +    reqs = cm.get_ready_requests()
> +
> +    assert len(reqs) > 0
> +
> +    # Process the captured frames
> +
> +    for req in reqs:
> +        buffers = req.buffers
> +
> +        assert len(buffers) == 1
> +
> +        # We want to re-queue the buffer we just handled. Instead of creating
> +        # a new Request, we re-use the old one. We need to call req.reuse()
> +        # to re-initialize the Request before queuing.
> +
> +        req.reuse()
> +        cam.queue_request(req)
> +
> +        scope = ctx['scope']
> +
> +        if 'num_frames' not in scope:
> +            scope['num_frames'] = 0
> +
> +        scope['num_frames'] += 1
> +
> +
> +def capture(ctx):
> +    cm = ctx['cm']
> +    cam = ctx['cam']
> +    reqs = ctx['reqs']
> +
> +    # Queue the requests to the camera
> +
> +    for req in reqs:
> +        ret = cam.queue_request(req)
> +        assert ret == 0
> +
> +    # Use Selector to wait for events from the camera and from the keyboard
> +
> +    sel = selectors.DefaultSelector()
> +    sel.register(cm.efd, selectors.EVENT_READ, lambda fd: handle_camera_event(ctx))
> +
> +    reqs = []
> +
> +    while ctx['running']:
> +        events = sel.select()
> +        for key, mask in events:
> +            key.data(key.fileobj)
> +
> +
> +def main():
> +    parser = argparse.ArgumentParser()
> +    parser.add_argument('-c', '--camera', type=str, default='1',
> +                        help='Camera index number (starting from 1) or part of the name')
> +    parser.add_argument('-f', '--format', type=str, help='Pixel format')
> +    parser.add_argument('-s', '--size', type=str, help='Size ("WxH")')
> +    args = parser.parse_args()
> +
> +    cm = libcam.CameraManager.singleton()
> +
> +    try:
> +        if args.camera.isnumeric():
> +            cam_idx = int(args.camera)
> +            cam = next((cam for i, cam in enumerate(cm.cameras) if i + 1 == cam_idx))
> +        else:
> +            cam = next((cam for cam in cm.cameras if args.camera in cam.id))
> +    except Exception:
> +        print(f'Failed to find camera "{args.camera}"')
> +        return -1
> +
> +    # Acquire the camera for our use
> +
> +    ret = cam.acquire()
> +    assert ret == 0
> +
> +    # Configure the camera
> +
> +    camconfig = cam.generate_configuration([libcam.StreamRole.StillCapture])
> +
> +    streamconfig = camconfig.at(0)
> +
> +    if args.format:
> +        fmt = libcam.PixelFormat(args.format)
> +        streamconfig.pixel_format = fmt
> +
> +    if args.size:
> +        w, h = [int(v) for v in args.size.split('x')]
> +        streamconfig.size = libcam.Size(w, h)
> +
> +    ret = cam.configure(camconfig)
> +    assert ret == 0
> +
> +    stream = streamconfig.stream
> +
> +    # Allocate the buffers for capture
> +
> +    allocator = libcam.FrameBufferAllocator(cam)
> +    ret = allocator.allocate(stream)
> +    assert ret > 0
> +
> +    num_bufs = len(allocator.buffers(stream))
> +
> +    print(f'Capturing {streamconfig} with {num_bufs} buffers from {cam.id}')
> +
> +    # Create the requests and assign a buffer for each request
> +
> +    reqs = []
> +    for i in range(num_bufs):
> +        # Use the buffer index as the "cookie"
> +        req = cam.create_request(i)
> +
> +        buffer = allocator.buffers(stream)[i]
> +        ret = req.add_buffer(stream, buffer)
> +        assert ret == 0
> +
> +        reqs.append(req)
> +
> +    # Start the camera
> +
> +    ret = cam.start()
> +    assert ret == 0
> +
> +    # Create a scope for the IPython shell
> +    scope = {
> +        'cm': cm,
> +        'cam': cam,
> +        'libcam': libcam,
> +    }
> +
> +    # Create a simple context shared between the background thread and the main
> +    # thread.
> +    ctx = {
> +        'running': True,
> +        'cm': cm,
> +        'cam': cam,
> +        'reqs': reqs,
> +        'scope': scope,
> +    }
> +
> +    # Note that "In CPython, due to the Global Interpreter Lock, only one thread
> +    # can execute Python code at once". We rely on that here, which is not very
> +    # nice. I am sure an fd-based polling loop could be integrated with IPython,
> +    # somehow, which would allow us to drop the threading.
> +
> +    t = threading.Thread(target=capture, args=(ctx,))
> +    t.start()
> +
> +    IPython.embed(banner1="", exit_msg="", confirm_exit=False, user_ns=scope)
> +
> +    print("Exiting...")
> +
> +    ctx["running"] = False
> +    t.join()
> +
> +    # Stop the camera
> +
> +    ret = cam.stop()
> +    assert ret == 0
> +
> +    # Release the camera
> +
> +    ret = cam.release()
> +    assert ret == 0
> +
> +    return 0
> +
> +
> +if __name__ == '__main__':
> +    sys.exit(main())

-- 
Regards,

Laurent Pinchart