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Jarkko Sakkinen
jarkko
Edited 1 month ago
Video streamed with ffmpeg, and played with ffplay through with my WiP V4L2 loopback driver.
The next step is to detach the producer from /dev/videoX fops and instead return anonymous inode, which owns a file where the capture device can write the video stream.
The video resolution in this smoke test is 640x480, and the encoder scales it up in real-time to 1280x720.
#linux #kernel #media #video4linux
The next step is to detach the producer from /dev/videoX fops and instead return anonymous inode, which owns a file where the capture device can write the video stream.
The video resolution in this smoke test is 640x480, and the encoder scales it up in real-time to 1280x720.
#linux #kernel #media #video4linux
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“Capture” for the next step, i.e. BuildRoot build for headless test.
wget https://file-examples.com/storage/fe3abb0cc967520c59b97f1/2018/04/file_example_AVI_640_800kB.avi
ffmpeg -stream_loop -1 -re -i file_example_AVI_640_800kB.avi -s 1280x720 -f v4l2 /dev/video0
Due to change for “/dev/video0” part (because capture device is a file descriptor eventually). Then I just need playback and comparison to get success/failure condition…
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Early, rudimentary and unpolished skeleton of a “server side”:
import ctypes
import fcntl
import os
import sys
V4L2_LOOPBACK_DEVICE_FILE = "/dev/v4l2loopback"
V4L2_LOOPBACK_MAGIC = 0x4C
V4L2_LOOPBACK_IOC_ADD = 0xC0004C00
class V4L2LoopbackAdd(ctypes.Structure):
_fields_ = [
("card_label", ctypes.c_uint64),
("flags", ctypes.c_uint16),
("device_nr", ctypes.c_uint16),
("card_fd", ctypes.c_uint32),
]
def main():
try:
fd = os.open(V4L2_LOOPBACK_DEVICE_FILE, os.O_RDWR)
except FileNotFoundError:
sys.exit(1)
loopback = V4L2LoopbackAdd()
ctypes.memset(ctypes.addressof(loopback), 0, ctypes.sizeof(loopback))
try:
fcntl.ioctl(fd, V4L2_LOOPBACK_IOC_ADD, loopback)
print(f"{loopback.device_nr} {loopback.card_fd}")
except OSError:
sys.exit(1)
finally:
os.close(fd)
if __name__ == "__main__":
main()
Anyway shows the gist. The device name is due to change…
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