ioctl VIDIOC_STREAMON, VIDIOC_STREAMOFF
&manvol;

# VIDIOC_STREAMON

# VIDIOC_STREAMOFF

Start or stop streaming I/O

    	int ioctl
    	int fd
    	int request
    	const int *argp

## Arguments

`fd`

  &fd;

`request`

  VIDIOC_STREAMON, VIDIOC_STREAMOFF

`argp`

## Description

The `VIDIOC_STREAMON` and `VIDIOC_STREAMOFF` ioctl start and stop the capture or output process during streaming (memory mapping or user pointer) I/O.

Specifically the capture hardware is disabled and no input buffers are filled (if there are any empty buffers in the incoming queue) until `VIDIOC_STREAMON` has been called. Accordingly the output hardware is disabled, no video signal is produced until `VIDIOC_STREAMON` has been called. The ioctl will succeed when at least one output buffer is in the incoming queue.

The `VIDIOC_STREAMOFF` ioctl, apart of aborting or finishing any DMA in progress, unlocks any user pointer buffers locked in physical memory, and it removes all buffers from the incoming and outgoing queues. That means all images captured but not dequeued yet will be lost, likewise all images enqueued for output but not transmitted yet. I/O returns to the same state as after calling &VIDIOC-REQBUFS; and can be restarted accordingly.

Both ioctls take a pointer to an integer, the desired buffer or stream type. This is the same as &v4l2-requestbuffers; type.

If `VIDIOC_STREAMON` is called when streaming is already in progress, or if `VIDIOC_STREAMOFF` is called when streaming is already stopped, then the ioctl does nothing and 0 is returned.

Note that applications can be preempted for unknown periods right before or after the `VIDIOC_STREAMON` or `VIDIOC_STREAMOFF` calls, there is no notion of starting or stopping "now". Buffer timestamps can be used to synchronize with other events.

&return-value;

EINVAL

  The buffertype is not supported, or no buffers have been allocated (memory mapping) or enqueued (output) yet.

EPIPE

  The driver implements pad-level format configuration and the pipeline configuration is invalid.