README

Video4L2 capture and controls enumeration component for Lazarus

Version 1.0.1

Copyright (C) 2013 Yuriy Pilgun

Usage

See provided demo project.

OnFrame event

There are two events OnFrame and OnFrameSynchronized. The first OnFrame runs in context of Capturing thread, so you can't draw on Form inside it, but you can convert data if you wish. To draw data on Form you should use OnFrameSynchronized, which is executed in context of the main thread.

libv4l2

You can try to set {$define USELIBV4L2} to use libv4l2.so wrapper library. It has some advantages such as providing automatic color space conversion to RGB24 (BGR24) or YUV420 (YVU420) for cameras that don't support them natively.

Caveats

Make sure you don't destroy objects needed to draw a frame before stopping video capture thread. If you placed TVideo4L2Device on a form it will be destroyed automatically, but at wrong time. You probably will need some temporary bitmap to draw frames from OnFrameSynchronized event. If you free this temporary bitmap in TForm.OnDestroy event, it will be destroyed BEFORE stopping video, and synchronized call from capture thread will get Access Violation exception. To fix this issue free video object explicitly:

procedure TForm1.FormDestroy(Sender: TObject);
begin
  Video4L2Device1.Free; // <- this will stop capture thread before destroying other objects
  TempBitmap.Free;
end;

License

This program is provided under the terms of the MIT License.