py: examples: Add simple-capture.py

Add an example to showcase the more-or-less minimal capture case.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/py/examples/simple-capture.py

@@ -0,0 +1,162 @@
+#!/usr/bin/env python3
+
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright (C) 2022, Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
+
+# A simple capture example showing:
+# - How to setup the camera
+# - Capture certain number of frames in a blocking manner
+# - How to stop the camera
+#
+# This simple example is, in many ways, too simple. The purpose of the example
+# is to introduce the concepts. A more realistic example is given in
+# simple-continuous-capture.py.
+
+import argparse
+import libcamera as libcam
+import sys
+
+# Number of frames to capture
+TOTAL_FRAMES = 30
+
+
+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
+
+    cam_config = cam.generate_configuration([libcam.StreamRole.Viewfinder])
+
+    stream_config = cam_config.at(0)
+
+    if args.format:
+        fmt = libcam.PixelFormat(args.format)
+        stream_config.pixel_format = fmt
+
+    if args.size:
+        w, h = [int(v) for v in args.size.split('x')]
+        stream_config.size = libcam.Size(w, h)
+
+    ret = cam.configure(cam_config)
+    assert ret == 0
+
+    print(f'Capturing {TOTAL_FRAMES} frames with {stream_config}')
+
+    stream = stream_config.stream
+
+    # Allocate the buffers for capture
+
+    allocator = libcam.FrameBufferAllocator(cam)
+    ret = allocator.allocate(stream)
+    assert ret > 0
+
+    num_bufs = len(allocator.buffers(stream))
+
+    # 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
+
+    # frames_queued and frames_done track the number of frames queued and done
+
+    frames_queued = 0
+    frames_done = 0
+
+    # Queue the requests to the camera
+
+    for req in reqs:
+        ret = cam.queue_request(req)
+        assert ret == 0
+        frames_queued += 1
+
+    # The main loop. Wait for the queued Requests to complete, process them,
+    # and re-queue them again.
+
+    while frames_done < TOTAL_FRAMES:
+        # cm.get_ready_requests() blocks until there is an event and returns
+        # all the ready requests. Here we should almost always get a single
+        # Request, but in some cases there could be multiple or none.
+
+        reqs = cm.get_ready_requests()
+
+        for req in reqs:
+            frames_done += 1
+
+            buffers = req.buffers
+
+            # A ready Request could contain multiple buffers if multiple streams
+            # were being used. Here we know we only have a single stream,
+            # and we use next(iter()) to get the first and only buffer.
+
+            assert len(buffers) == 1
+
+            stream, fb = next(iter(buffers.items()))
+
+            # Here we could process the received buffer. In this example we only
+            # print a few details below.
+
+            meta = fb.metadata
+
+            print("seq {:3}, bytes {}, frames queued/done {:3}/{:<3}"
+                  .format(meta.sequence,
+                          '/'.join([str(p.bytes_used) for p in meta.planes]),
+                          frames_queued, frames_done))
+
+            # If we want to capture more frames we need to queue more Requests.
+            # We could create a totally new Request, but it is more efficient
+            # to reuse the existing one that we just received.
+            if frames_queued < TOTAL_FRAMES:
+                req.reuse()
+                cam.queue_request(req)
+                frames_queued += 1
+
+    # 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())