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#!/usr/bin/env python3
# SPDX-License-Identifier: BSD-3-Clause
# Copyright (C) 2022, Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
# A simple capture example extending the simple-capture.py example:
# - Capture frames using events from multiple cameras
# - Listening events from stdin to exit the application
# - Memory mapping the frames and calculating CRC
import binascii
import libcamera as libcam
import libcamera.utils
import selectors
import sys
# A container class for our state per camera
class CameraCaptureContext:
idx: int
cam: libcam.Camera
reqs: list[libcam.Request]
mfbs: dict[libcam.FrameBuffer, libcamera.utils.MappedFrameBuffer]
def __init__(self, cam, idx):
self.idx = idx
self.cam = cam
# 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)
ret = cam.configure(cam_config)
assert ret == 0
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))
print(f'cam{idx} ({cam.id}): capturing {num_bufs} buffers with {stream_config}')
# Create the requests and assign a buffer for each request
self.reqs = []
self.mfbs = {}
for i in range(num_bufs):
# Use the buffer index as the "cookie"
req = cam.create_request(idx)
buffer = allocator.buffers(stream)[i]
ret = req.add_buffer(stream, buffer)
assert ret == 0
self.reqs.append(req)
# Save a mmapped buffer so we can calculate the CRC later
self.mfbs[buffer] = libcamera.utils.MappedFrameBuffer(buffer).mmap()
def uninit_camera(self):
# Stop the camera
ret = self.cam.stop()
assert ret == 0
# Release the camera
ret = self.cam.release()
assert ret == 0
# A container class for our state
class CaptureContext:
cm: libcam.CameraManager
camera_contexts: list[CameraCaptureContext] = []
def handle_camera_event(self):
# cm.get_ready_requests() will not block here, as we know there is an event
# to read.
reqs = self.cm.get_ready_requests()
# Process the captured frames
for req in reqs:
self.handle_request(req)
return True
def handle_request(self, req: libcam.Request):
cam_ctx = self.camera_contexts[req.cookie]
buffers = req.buffers
assert len(buffers) == 1
# 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.
stream, fb = next(iter(buffers.items()))
# Use the MappedFrameBuffer to access the pixel data with CPU. We calculate
# the crc for each plane.
mfb = cam_ctx.mfbs[fb]
crcs = [binascii.crc32(p) for p in mfb.planes]
meta = fb.metadata
print('cam{:<6} seq {:<6} bytes {:10} CRCs {}'
.format(cam_ctx.idx,
meta.sequence,
'/'.join([str(p.bytes_used) for p in meta.planes]),
crcs))
# 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_ctx.cam.queue_request(req)
def handle_key_event(self):
sys.stdin.readline()
print('Exiting...')
return False
def capture(self):
# Queue the requests to the camera
for cam_ctx in self.camera_contexts:
for req in cam_ctx.reqs:
ret = cam_ctx.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(sys.stdin, selectors.EVENT_READ, self.handle_key_event)
sel.register(self.cm.event_fd, selectors.EVENT_READ, lambda: self.handle_camera_event())
running = True
while running:
events = sel.select()
for key, mask in events:
# If the handler return False, we should exit
if not key.data():
running = False
def main():
cm = libcam.CameraManager.singleton()
ctx = CaptureContext()
ctx.cm = cm
for idx, cam in enumerate(cm.cameras):
cam_ctx = CameraCaptureContext(cam, idx)
ctx.camera_contexts.append(cam_ctx)
# Start the cameras
for cam_ctx in ctx.camera_contexts:
ret = cam_ctx.cam.start()
assert ret == 0
ctx.capture()
for cam_ctx in ctx.camera_contexts:
cam_ctx.uninit_camera()
return 0
if __name__ == '__main__':
sys.exit(main())
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