Struct v4l::io::dmabuf::stream::StreamManual

pub struct StreamManual { /* private fields */ }

A stream using the manual buffer management API, where owned buffers are handed to the user, to be enqueued and dequeued explicitly, rather than only borrowed.

Implementations

impl StreamManual

pub fn new(dev: &Device, buf_type: Type, buf_count: u32) -> Result<Self>

Returns an advanced, buffer-owning stream for frame capturing.

Currently allows only one buffer to be in flight.

Arguments

• dev - Device ref to get its file descriptor
• buf_type - Type of the buffers
• buf_count - the number of buffers to allocate. Too many buffers will hog memory, too few will give less processing time for each buffer (although that doesn’t matter with this API). A safe number is 4.

Example

use v4l::buffer::Type;
use v4l::device::Device;
use v4l::io::dmabuf::StreamManual;

let dev = Device::new(0);
if let Ok(dev) = dev {
    let stream = StreamManual::new(&dev, Type::VideoCapture, 4);
}

pub fn start(&mut self) -> Result<DmaBufProtected>

Returns an uninitialized buffer for immediate queueing in cycle_buffer and starts the stream.

pub fn finish( self, buf: DmaBufProtected, ) -> Result<(), (Error, DmaBufProtected, Self)>

Stops the stream and deallocates buffers.

pub fn cycle_buffer( &mut self, buf: DmaBufProtected, ) -> Result<(DmaBufProtected, Metadata)>

Returns a buffer and removes a new buffer once it’s ready.

This will lock the buffer passed in for writing, so the buffer must be unlocked in a timely fashion. Watch out for deadlocks!

FIXME: if this fails, the buffer is swallowed and streaming can’t continue due to no free buffers.