encoders.py 文件源码

def _callback_write(self, buf, key=PiVideoFrameType.frame):
        """
        Overridden to strip alpha bytes when required.
        """
        if self._strip_alpha:
            s = ct.string_at(buf[0].data, buf[0].length)
            s = bytearray(s)
            del s[3::4]
            # All this messing around with buffers is to work around some issue
            # with MMAL or ctypes (I'm not sure which is at fault). Anyway, the
            # upshot is that if you fiddle with buf[0].data in any way
            # whatsoever (even if you make every attempt to restore its value
            # afterward), mmal_port_disable locks up when we call it in stop()
            new_buf = mmal.MMAL_BUFFER_HEADER_T.from_buffer_copy(buf[0])
            new_buf.length = len(s)
            new_buf.data = ct.pointer(ct.c_uint8.from_buffer(s))
            return super(PiRawMixin, self)._callback_write(ct.pointer(new_buf), key)
        else:
            return super(PiRawMixin, self)._callback_write(buf, key)