www.Conscious-Robots.com - Machine Consciousness - Re:Simulated WebCam exception in QueryFrame

Lo Último
Programación en VPL de un control básico para el robot Lego NXT Alpha-Rex Uso de los Servicios de Lego NXT en VPL Algunos trucos de VPL Programación en VPL. Encendiendo la luz intermitente Programación en VPL. Explorador Ultrasónico con Lego NXT Gestionando la ejecución de un un programa en el Lego NXT Tutorial de Robótica en VPL. Drive by Wire

Lo más visto
Foro de debate PSYCHE-D MobileRobots Pioneer 3 (P3 DX) Análisis I-Cybie Robótica Cognitiva Un Robot en Cada Casa Aprendiendo a usar Microsoft Robotics Studio (MSRS) IA Fuerte y Conciencia Artificial

Conscious-Robots.com Forum

Ruta :: Lista de foros

Robotics Forums

Microsoft Robotics Studio

Raúl

Moderador

Mensajes: 432

Karma: 6

Simulated WebCam exception in QueryFrame - 2007/09/18 12:31 I found a bug in the Robotics Studio SimulatedWebcam service.

The problem is that after a few seconds (some times it takes longer) I get an InvalidOperationException in the QueryFrameHandler method in file SimulatedWebcam.cs (The lines causing the exception are these:

Code:


 // size not specified
if(size.Width == 0)
  size = _state.Image.Size;

see the rest of the code below)

The runtime is complaining because Object (_state.Image) is currently in use elsewhere.

I think the size assignment should be moved within the next try-catch. Also the method QueryFrameHandler should declared as Exclusive, because the image is being locked in the method.

Microsoft are making these changes for the next release.

Code:


 [ServiceHandler(ServiceHandlerBehavior.Concurrent)]

public IEnumerator<ITask> QueryFrameHandler(webcam.QueryFrame query)

{

if (_state.Image == null)
{
query.ResponsePort.Post(new webcam.QueryFrameResponse());
yield break;
}

Size size = new Size((int)query.Body.Size.X, (int)query.Body.Size.Y);

if (query.Body.Format == Guid.Empty)
{

// raw image requested;
BitmapData raw = null;

 // size not specified
if(size.Width == 0)
  size = _state.Image.Size;

try
{
raw = _state.Image.LockBits(new Rectangle(Point.Empty, size),
ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
int byteSize = raw.Height * raw.Stride;
webcam.QueryFrameResponse response = new webcam.QueryFrameResponse();

response.TimeStamp = _state.LastFrameUpdate;
response.Frame = new byte[byteSize];
response.Size = new Size(raw.Width, raw.Height);
response.Format = Guid.Empty;
System.Runtime.InteropServices.Marshal.Copy(raw.Scan0, response.Frame, 0, byteSize);
query.ResponsePort.Post(response);
}

catch (Exception ex)
{
query.ResponsePort.Post(Fault.FromException(ex));
}

finally
{
if (raw != null)
{

_state.Image.UnlockBits(raw);

}
}
}

else
{

ImageFormat format = new ImageFormat(query.Body.Format);
using (MemoryStream stream = new MemoryStream())
{ 
if (size == _state.Image.Size ||
size.Width == 0 ||
size.Height == 0 ||
size.Width >= _state.Image.Width ||
size.Height >= _state.Image.Height)
{
size = _state.Image.Size;
_state.Image.Save(stream, format);
}
else
{
using (Bitmap temp = new Bitmap(
_state.Image, size))
{
temp.Save(stream, format);
}
}

webcam.QueryFrameResponse response = new webcam.QueryFrameResponse();
response.TimeStamp = _state.LastFrameUpdate;
response.Frame = new byte[(int)stream.Length];
response.Size = size;
response.Format = format.Guid;
stream.Position = 0;
stream.Read(response.Frame, 0, response.Frame.Length);
query.ResponsePort.Post(response);
}
}

yield break;
}

Post edited by: Raúl, at: 2007/09/18 12:45 Raúl Arrabales Moreno. conscious-robots.com/raul

El administrador ha deshabilitado la escritura de mensajes a los usuarios no registrados.

Raúl

Moderador

Mensajes: 432

Karma: 6

Re:Simulated WebCam exception in QueryFrame - 2007/09/18 13:25 The code after making the mentioned changes is as follows (this code seems to work ok. I am unsure whether or not some frames are loss when the method is called when the simulator engine has blocked the image).

Code:


         // Raul - Service handler changed from Concurrent to Exclusive.
        [ServiceHandler(ServiceHandlerBehavior.Exclusive)]
        public IEnumerator<ITask> QueryFrameHandler(webcam.QueryFrame query)
        {
            if (_state.Image == null)
            {
                query.ResponsePort.Post(new webcam.QueryFrameResponse());
                yield break;
            }

            Size size = new Size((int)query.Body.Size.X, (int)query.Body.Size.Y);

            if (query.Body.Format == Guid.Empty)
            {
                // raw image requested;
                BitmapData raw = null;


                try
                {
                    // Raul - This check moved into the try-catch block.
                    // size not specified
                    if (size.Width == 0)
                        size = _state.Image.Size;

                    raw = _state.Image.LockBits(new Rectangle(Point.Empty, size),
                        ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);

                    int byteSize = raw.Height * raw.Stride;

                    webcam.QueryFrameResponse response = new webcam.QueryFrameResponse();

                    response.TimeStamp = _state.LastFrameUpdate;
                    response.Frame = new byte[byteSize];
                    response.Size = new Size(raw.Width, raw.Height);
                    response.Format = Guid.Empty;

                    System.Runtime.InteropServices.Marshal.Copy(raw.Scan0, response.Frame, 0, byteSize);

                    query.ResponsePort.Post(response);
                }
                catch (Exception ex)
                {
                    query.ResponsePort.Post(Fault.FromException(ex));
                }
                finally
                {
                    if (raw != null)
                    {
                        _state.Image.UnlockBits(raw);
                    }
                }
            }
            else
            {
                ImageFormat format = new ImageFormat(query.Body.Format);

                using (MemoryStream stream = new MemoryStream())
                {                    
                    if (size == _state.Image.Size ||
                        size.Width == 0 ||
                        size.Height == 0 ||
                        size.Width >= _state.Image.Width ||
                        size.Height >= _state.Image.Height)
                    {
                        size = _state.Image.Size;
                        _state.Image.Save(stream, format);
                    }
                    else
                    {
                        using (Bitmap temp = new Bitmap(
                            _state.Image, size))
                        {
                            temp.Save(stream, format);
                        }
                    }


                    webcam.QueryFrameResponse response = new webcam.QueryFrameResponse();
                    response.TimeStamp = _state.LastFrameUpdate;
                    response.Frame = new byte[(int)stream.Length];
                    response.Size = size;
                    response.Format = format.Guid;

                    stream.Position = 0;
                    stream.Read(response.Frame, 0, response.Frame.Length);

                    query.ResponsePort.Post(response);
                }
            }
            yield break;
        }

Raúl Arrabales Moreno. conscious-robots.com/raul

El administrador ha deshabilitado la escritura de mensajes a los usuarios no registrados.

Ruta :: Lista de foros Robotics Forums Microsoft Robotics Studio