Changing FrameSize

[Sc0rpe]

Hi, i am currently developing a camera server with your library. Therefore i am running the Frame aquisition in a loop. In this loop i am receiving messages via MPSC. When i receive such a message i want to change the video frame size. For my trials i had rebuild your video_capture example. After i change video size i tried to rebuild the framebuffers and create new request with them. However when it executes the allocation let mut framebuff = alloc.alloc(&stream).unwrap(); of the new framebuffers i get an error [0:22:47.613844067] [1719] ERROR V4L2 v4l2_videodevice.cpp:1352 /dev/video14[13:cap]: Buffers already allocated

My code looks like this

let mut cfgs = actcam.generate_configuration(&[StreamRole::Raw]).unwrap();
cfgs.get_mut(0).unwrap().set_size(Size{width: new_width, height: new_height});
cfgs.validate();
actcam.configure(&mut cfgs).expect("Unable to configure camera");

// Allocate frame buffers for the stream
let cfg = cfgs.get(0).unwrap();
let mut stream = cfg.stream().unwrap();
let mut framebuff = alloc.alloc(&stream).unwrap(); // this gives me error "buffers already allocated" from V4L2
...
//creating request with the new buffer

I guess i have to free or drop the old framebuffers somehow. Is there a function for that? I couldn't find anything that suits my needs. Also for the requests. As in the video_capture example i do like

// Recycle the request back to the camera for execution                   
req.reuse(ReuseFlag::REUSE_BUFFERS);
actcam.queue_request(req).unwrap();   

after changing the video size i guess i have to remove the old requests and just queue the new ones. Is there anything i can do to clean the request list and remove the old requests?

[chemicstry]

Hi,

It could be that some deallocation methods are missing in the rust bindings. Do you know any C/C++ libcamera example that does size reconfiguration while running? It would help debugging knowing what is the correct sequence of calls.

[Sc0rpe]

Unfortunately i couldn't find anything about resizing the video while running.

[chemicstry]

I tested this by taking video_capture example and duplicating everything after cam.acquire(). The only thing needed was to call cam.stop() in between two blocks. See here: https://gist.github.com/chemicstry/2326de3367c010445806a53b8e4ef284

I think your problem was that you did not drop FrameBufferAllocator, which resulted in the same error for me.

I created a PR to fix that, please try if it helps: https://github.com/lit-robotics/libcamera-rs/pull/24

[Sc0rpe]

Thanks to your hints i could manage to resize the video while running! It seems it is necessary to drop and create a new CameraConfiguration (i reused the existing one, just set a new size) to get it working. let mut cfgs = cam.generate_configuration(&[StreamRole::VideoRecording]).unwrap(); Without this line in advance to buil the new buffers, it didn't worked for me! However i still have the problem to clean the request queue for the camera. In your example you don't have this problem because you let the loop finish, then starting a new one. After resizing, but before queuing the newly created requests, i do as following:

  let b = cfgs.get_mut(0).unwrap().get_buffer_count(); // getting number of buffers used
  for i in 1..b {
      if let Ok(req) = rx.recv_timeout(Duration::from_secs(2)) {};
      thread::sleep(Duration::from_micros(1)); // not sure if i need it
  }
  ...
  // queuing new request

Do you think this is an appropriate solution or might this fail or cause problems in another way?

So far, thank you very much for your help!!!

[chemicstry]

When you call ActiveCamera::stop() it will immediately complete all queued requests with RequestStatus::Cancelled. libcamera docs say that all requests are completed synchronously when calling stop(), so you should be able to just do this:

cam.stop().unwrap();
while let Ok(_) = rx.try_recv() {}

[Sc0rpe]

Thanks for the information. Works like a charm! This issue is solved for me. Thank you very much for your help!