TCameraComponent和TVideoCaptureDevice不在Win32中初始化

问题描述

我使用标准代码初始化TVideoCaptureDevice并开始捕获。

I use the standard code to initialize TVideoCaptureDevice and start capturing.

const  M_LAUNCH_CAMERA = WM_APP + 450;
type
  TCamSF1 = class(TForm)
...
  protected
    procedure LaunchCamera(var Message: TMessage); message M_LAUNCH_CAMERA;
...
end;
...
procedure TCamSF1.LaunchCamera(var Message: TMessage);
begin
if VideoCamera = nil then
    begin
      VideoCamera := TCaptureDeviceManager.Current.DefaultVideoCaptureDevice;
      if VideoCamera <> nil then
      begin
        VideoCamera.OnSampleBufferReady := CameraReady;
        VideoCamera.StartCapture;
      end
      else
      begin
        Caption := 'Video capture devices not available.';
      end;
    end
    else
    begin
      VideoCamera.StartCapture;
    end;
end;

procedure TCamSF1.IdTCPServer1Execute(AContext: TIdContext);
var
  S: AnsiString;
  Command: TAnsiStrings;
  Msg: TMessage;
begin
  if (AContext <> nil) and (AContext.Connection.Socket.Connected) and
    (not AContext.Connection.Socket.InputBufferIsEmpty) then
    S := AContext.Connection.Socket.ReadLn;
  if S = '' then
    exit;
  Memo1.Lines.Add(S);
  Command := ParseCommandString(S, '#');
  if Command[0] = 'camresol' then
  begin
    CamShotParams := Command;
    Msg.Msg := M_LAUNCH_CAMERA;
    Dispatch(Msg);
  end;
end;

当我从按钮OnClick事件发送消息时，但从TIdTCPServer OnExecute摄像机无法启动，并且 Caption：='视频捕获设备不可用。'正在运行。而且，在此之后，相机甚至不会从Button OnClick事件中初始化。

The code properly works when I dispatch a message from a button OnClick event but when the message is dispatched from TIdTCPServer OnExecute the camera does not start and Caption := 'Video capture devices not available.' is run. Moreover, after this the camera does not initialize even from the Button OnClick event.

在直接调用

VideoCamera := TCaptureDeviceManager.Current.DefaultVideoCaptureDevice;
if VideoCamera <> nil then
  begin
    VideoCamera.OnSampleBufferReady := CameraReady;
    VideoCamera.StartCapture;
  end;

。虽然从Button OnClick运行时效果很好。
使用TCameraComponent会导致相同的问题。
如果在Form OnCreate事件中处理了相机初始化，则可以解决此问题，但这不适合，因为两个或多个应用程序不允许同时使用相机。

from within Server OnExecute event. Though it works fine when run from the Button OnClick.Using of TCameraComponent cause the same problems.This issue could be reolved if camera initialization is handled in Form OnCreate event but this is not suitable as simultaneous usage of camera is not allowed by two or more applications.

推荐答案

似乎，捕获设备应该从主线程进行初始化和操作。尝试将捕获操作包装在TThread.Synchronize类过程中，如下所示：

It seems, capture device should be initialized and manipulated from the main thread. Try to wrap capture manipulating in TThread.Synchronize class procedure, smth like this:

procedure TMyForm.IdTCPServer1Execute(AContext: TIdContext);
...
begin
...
TThread.Synchronize(nil,
  procedure
  begin
    DoSmthWithCamera();
  end;
);
...
end;

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