Correctly Using the IDeckLinkGLScreenPreviewHelper in C#

Hi again,

At this point I've got the framerate issue sorted out (thanks Nick!) but that didn't fix my black GL surface like I was hoping it would. I've followed the documentation's instructions and mimicked the functional CapturePreview C++ as much as possible but can't seem to get the frames to show. I've tested the SharpGL surface with other GL tasks and confirmed that it is functional, which means that I might not understand or have correctly implemented either the GLScreenPreviewHelper, or perhaps I've simply not setup the orthographic projection correctly (code adapted from documentation). I've confirmed the settings and device to be correct (by debugging the C++ project).

So that being said, does the code below look like I've correctly setup the surface and established the correct GL frame setting/painting sequence?

Thanks,
Andrew

Code: Select all

public partial class FormSharpGLTexturesSample : Form, IDeckLinkScreenPreviewCallback
    {
        private IDeckLinkInput m_deckLinkInput;
        private IDeckLinkGLScreenPreviewHelper m_deckLinkScreenPreviewHelper;
        private int frameCount = 0;
        private bool glIsInitialized = false;

        public FormSharpGLTexturesSample()
        {
            InitializeBlackMagicDevice();

            InitializeComponent();

            //SharpGL.OpenGL gl = this.openGLControl1.OpenGL;
            //gl.Enable(OpenGL.GL_TEXTURE_2D);

            openGLControl1.OpenGL.RenderContextProvider.MakeCurrent();
            m_deckLinkScreenPreviewHelper.InitializeGL();
            openGLControl1.OpenGL.MakeNothingCurrent();

            glIsInitialized = true;
        }

        private void InitializeBlackMagicDevice()
        {
            IDeckLink m_deckLink;
            IDeckLinkIterator deckLinkIterator = new CDeckLinkIterator();
            deckLinkIterator.Next(out m_deckLink);

            m_deckLinkScreenPreviewHelper = new CDeckLinkGLScreenPreviewHelper();

            m_deckLinkInput = (IDeckLinkInput)m_deckLink;
            m_deckLinkInput.SetScreenPreviewCallback(this);

            m_deckLinkInput.EnableVideoInput(_BMDDisplayMode.bmdModeHD720p5994, _BMDPixelFormat.bmdFormat8BitYUV, _BMDVideoInputFlags.bmdVideoInputFlagDefault);
            //m_deckLinkInput.EnableAudioInput(_BMDAudioSampleRate.bmdAudioSampleRate48kHz, _BMDAudioSampleType.bmdAudioSampleType16bitInteger, 2);
            m_deckLinkInput.StartStreams();

        }

        public void DrawFrame(IDeckLinkVideoFrame theFrame)
        {
            if (!glIsInitialized) return;

            m_deckLinkScreenPreviewHelper.SetFrame(theFrame);

            openGLControl1.OpenGL.RenderContextProvider.MakeCurrent();
            m_deckLinkScreenPreviewHelper.PaintGL();
            openGLControl1.OpenGL.MakeNothingCurrent();

            System.Runtime.InteropServices.Marshal.ReleaseComObject(theFrame);
            //frameCount++;
        }

        private void openGLControl1_OpenGLDraw(object sender, RenderEventArgs e)
        {
            SharpGL.OpenGL gl = this.openGLControl1.OpenGL;

            gl.Viewport(0, 0, (int)openGLControl1.Width, (int)openGLControl1.Height);
            gl.MatrixMode(MatrixMode.Projection);
            gl.LoadIdentity();
            gl.Ortho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
            gl.MatrixMode(MatrixMode.Modelview);

            //this.label1.Text = frameCount.ToString();
        }

    }


[Waqqas Sharif]

Hi Andrew,

I have played around with your C# code and managed to get it running.

Capture2.PNG (19.25 KiB) Viewed 1854 times

See the code below.

Code: Select all

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Imaging;
using System.Text;
using System.Windows.Forms;

using DeckLinkAPI;
using SharpGL;
using SharpGL.SceneGraph.Assets;

namespace SharpGLTexturesSample
{
    public partial class FormSharpGLTexturesSample : Form, IDeckLinkScreenPreviewCallback
    {
        private IDeckLinkInput m_deckLinkInput;
        private IDeckLinkGLScreenPreviewHelper m_deckLinkScreenPreviewHelper;
        private int frameCount = 0;
        private bool glIsInitialized = false;

        public FormSharpGLTexturesSample()
        {
            InitializeComponent();

            InitializeBlackMagicDevice();

            SharpGL.OpenGL gl = this.openGLControl1.OpenGL;

            gl.RenderContextProvider.MakeCurrent();
            m_deckLinkScreenPreviewHelper.InitializeGL();

            glIsInitialized = true;
        }

        private void InitializeBlackMagicDevice()
        {
            IDeckLink m_deckLink;
            IDeckLinkIterator deckLinkIterator = new CDeckLinkIterator();
            deckLinkIterator.Next(out m_deckLink);

            m_deckLinkScreenPreviewHelper = new CDeckLinkGLScreenPreviewHelper();

            m_deckLinkInput = (IDeckLinkInput)m_deckLink;
            m_deckLinkInput.SetScreenPreviewCallback(this);

            m_deckLinkInput.EnableVideoInput(_BMDDisplayMode.bmdModeHD720p5994, _BMDPixelFormat.bmdFormat8BitYUV, _BMDVideoInputFlags.bmdVideoInputFlagDefault);
            //m_deckLinkInput.EnableAudioInput(_BMDAudioSampleRate.bmdAudioSampleRate48kHz, _BMDAudioSampleType.bmdAudioSampleType16bitInteger, 2);
            m_deckLinkInput.StartStreams();
        }

        public void DrawFrame(IDeckLinkVideoFrame theFrame)
        {
            if (!glIsInitialized) return;

            m_deckLinkScreenPreviewHelper.SetFrame(theFrame);

            SharpGL.OpenGL gl = this.openGLControl1.OpenGL;

            gl.Translate(-1.5f, 0.0f, -6.0f);            // Move Left And Into The Screen
           
            gl.Flush();

            m_deckLinkScreenPreviewHelper.PaintGL();

            System.Runtime.InteropServices.Marshal.ReleaseComObject(theFrame);
        }

        private void openGLControl1_OpenGLDraw(object sender, RenderEventArgs e)
        {
            SharpGL.OpenGL gl = this.openGLControl1.OpenGL;

            gl.Viewport(0, 0, (int)openGLControl1.Width, (int)openGLControl1.Height);

            gl.MatrixMode(SharpGL.Enumerations.MatrixMode.Projection);
            gl.LoadIdentity();
            gl.Ortho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
            gl.MatrixMode(SharpGL.Enumerations.MatrixMode.Modelview);

            gl.Clear(OpenGL.GL_COLOR_BUFFER_BIT | OpenGL.GL_DEPTH_BUFFER_BIT);   // Clear The Screen And The Depth Buffer
            gl.LoadIdentity();               // Reset The View

            m_deckLinkScreenPreviewHelper.PaintGL();

            return;
        }

    }
}


You also need to specify FBO as the RenderContextType for OpenGLControl1 as opposed to DIBSection.

this.OpenGLControl1.RenderContextType = SharpGL.RenderContextType.FBO;

See this helps.