0
我剛開始在Ubuntu 16.04.
v4l2文檔的示例代碼原樣(打開爲'rw')?
我試圖從運行V4L2 Python文檔樣本,即使用v4l2
(用於Python 3
):
$ cat demo4SO.py
#!/usr/bin/env python3
import v4l2
import fcntl
vd = open('/dev/video0', 'rw')
#vd = open('/dev/video0', 'r')
cp = v4l2.v4l2_capability()
fcntl.ioctl(vd, v4l2.VIDIOC_QUERYCAP, cp)
print("driver:",cp.driver)
print("card:",cp.card)
但我越來越:
$ python3 demo4SO.py
Traceback (most recent call last):
File "demo4SO.py", line 6, in <module>
vd = open('/dev/video0', 'rw')
ValueError: must have exactly one of create/read/write/append mode
即使與sudo.
一起運行,我也會得到相同的錯誤
試圖用 'W +'(或 'R +'),我可以打開:
$ python3 demo4SO.py
Traceback (most recent call last):
File "demo4SO.py", line 8, in <module>
vd = open('/dev/video0', "w+")
io.UnsupportedOperation: File or stream is not seekable.
如果我改變 'RW'(或 'W +' 或 'R +'),以 'R',代碼工作作爲預期。
$ cat demo4SO.py
#!/usr/bin/env python3
import v4l2
import fcntl
#vd = open('/dev/video0', 'rw')
vd = open('/dev/video0', 'r')
cp = v4l2.v4l2_capability()
fcntl.ioctl(vd, v4l2.VIDIOC_QUERYCAP, cp)
print("driver:",cp.driver)
print("card:",cp.card)
$ python3 demo4SO.py
driver: b'uvcvideo'
card: b'Intel(R) RealSense(TM) 410'
我的用戶名屬於該組的視頻設備,所以看起來問題並不涉及到權限:
$ groups
openstack root sudo video staff
$ ls -ls /dev/video0
0 crw-rw----+ 1 root video 81, 0 פבר 14 11:31 /dev/video0
任何想法,爲什麼我不能運行的文檔的示例代碼是('rw')?