picamera.exc.PiCameraMMALError: no buffers available: Resource temporarily unavailable; try again later

[smarti57]

I'm unable to run Crosshair example from Chap 16 without buffer issues on an RPI4 with the latest raspbian buster and both the binary version of picamera and a compiled version from the latest master. I do get frames that update in a non-periodic manner (maybe 0.2fps on average)

When running the example in both python 2.7.16 and python 3.7.3 I get the following against the latest version of picamera master,

Traceback (most recent call last):
  File "_ctypes/callbacks.c", line 232, in 'calling callback function'
  File "/usr/lib/python3/dist-packages/picamera/mmalobj.py", line 1227, in wrapper
    self._pool.send_buffer(block=False)
  File "/usr/lib/python3/dist-packages/picamera/mmalobj.py", line 1931, in send_buffer
    super(MMALPortPool, self).send_buffer(port, block, timeout)
  File "/usr/lib/python3/dist-packages/picamera/mmalobj.py", line 1881, in send_buffer
    raise PiCameraMMALError(mmal.MMAL_EAGAIN, 'no buffers available')
picamera.exc.PiCameraMMALError: no buffers available: Resource temporarily unavailable; try again later

[smarti57]

I tried the monkey patch from here, https://github.com/waveform80/picamera/issues/566

but have issues as I'm not using a picamera object, but rather MMALobjs.

[DdraigX]

@smarti57 what do you have to do with the patch to enable it? I am very green to python etc so any help would be appreciated. Currently my little raspberry pi project is working but getting this error.