Asynchronous vs Asynchonous connection

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Synchonous vs Asynchronous connection

Description

TVideoGrabber can connect to the IP cameras and URLs:

- synchronously if OpenURLAsync is disabled

In this case when invoking StartPreview() or StartRecording(), the function blocks until the connection succeeds or fails.

- synchronously if OpenURLAsync is enabled (default)

In this case, when invoking StartPreview() or StartRecording(), the function returns immediately so the main thread is not blocked and the application continues to respond to key and mouse events.

Once the connection is completed, the OnPreviewStarted() or OnRecordingStarted() event occurs to notify the application that the component is running.

If the connection fails, the OnLog event occurs with a "e_failed_to_start_preview" or "e_failed_to_start_recording" LogType error.

Example of generic StartPreview() / StartRecording() set of functions that handles the asynchronous connection result through the OnPreviewStarted() / OnRecordingStarted() and OnLog() events:

function StartPreview()
  VideoGrabber.OpenURLAsync = true // default
  VideoGrabber.VideoSource  = vs_IPCamera
  VideoGrabber.IPCameraURL = 

rtsp://192.168.0.25/axis-media/media.amp?videocodec=h264

  VideoGrabber.SetAuthentication (at_IPCamera, "root", "admin");
  VideoGrabber.StartPreview()
function StartRecord()
  VideoGrabber.OpenURLAsync = true // default
  VideoGrabber.VideoSource  = vs_IPCamera
  VideoGrabber.IPCameraURL = 

rtsp://192.168.0.25/axis-media/media.amp?videocodec=h264&audio=1
  VideoGrabber.SetAuthentication (at_IPCamera, "root", "admin");
  VideoGrabber.RecordingInNativeFormat = true
  VideoGrabber.RecordingMethod = rm_MP4
  VideoGrabber.AudioRecording = true
  VideoGrabber.StartRecording()
event function OnRecordingStartedEvent(Sender, Filename)
  ShowMessage (filename + " recording started!")
event function OnPreviewStartedEvent(Sender)
  ShowMessage ("preview started!")
event function OnLogEvent(Sender, Logtype, Severity, Errormsg)
  if (LogType = e_failed_to_start_recording) 
    ShowMessage ("error: recording failed to start")
  
  else if (LogType = e_failed_to_start_preview) 
    ShowMessage ("error: preview failed to start")