A class to easily generate AVI video with OpenGL and Video for Windows

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<li><a href='AviGenerator/AviGenerator_src.zip'>Download source files - 4 Kb</a></li>
<li><a href='AviGenerator/AviGenerator_demo.zip'>Download demo project - 24 Kb</a></li>
<li><a href='AviGenerator/AviGenerator_exe.zip'>Download executable - 9 Kb</a></li>
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<h2>Introduction</h2>
<p><code>CAviGenerator</code> is a simple wrapper for the Video For Windows (VFW) library. 
In the back, it takes care of a numerous initialization for you and hides the library function calls so
that the user can start generating movies in a minimal number of line of code and without having much knowledge about
VFW.</p>

<p>The class main features are: 
<ul>
<li>generation of AVI movies with any codec installed on your machine</li>
<li>no need of generating thousands of separate images,</li>
<li>simplicity of use</li>
</ul>
</p>

<p>The class <code>CAVIGenerator</code> takes it's inspiration from MSDN example <i>writeavi.c</i>.</p>


<h2>CAVIGenerator: A AVI Video wrapper</h2>

<p>A simple class that make creation of AVI video easy.</p>


<h3>Attributes</h3>

<p>Each object contains general charateristics of the movie such as 
<ul>
<li>the file name,</li>
<li>the frame rate, (fps)</li>
<li>the image description: <code>BITMAPINFOHEADER</code></li> 
These members are declared as protected and are accessible by Set methods.</p>

<p>It contains also private members that are used to handle the "Video for Windows"
AVI engine.</p>

<h3>Constructors</h3>

<pre>CAVIGenerator();
</pre>
<p>Default constructor, default file name is "Untitled.avi", frame rate is 30 fps.</p>

<pre>CAVIGenerator(LPCTSTR sFileName, CView* pView, DWORD dwRate);
</pre>
<p>In-place constructor with CView. See <code>SetBitmapHeader(CView* pView)</code>.</p>

<pre>CAVIGenerator(LPCTSTR sFileName, LPBITMAPINFOHEADER lpbih, DWORD dwRate);
</pre>
<p>In-place constructor with <code>BITMAPINFOHEADER</code>. See <code>SetBitmapHeader(LPBITMAPINFOHEADER lpbih)</code></p>


<h3>Setters and Getters</h3>

<pre>void SetFileName(const CString& _sFileName)
</pre>
<p><code>SetFileName</code> sets the name of the output file. The filename extension should be 
<i>.avi</i> otherwize the creation of the AVI won't work. Checking of .avi extension
is left to the user.</p>

<pre>void SetRate(DWORD dwRate)
</pre>	
<p><code>SetRate</code> sets the frame rate (fps).</p>

<pre>void SetBitmapHeader(CView* pView);
</pre>	
<p><code>SetBitmapHeader</code> fills in the information about the bitmap
in <code>m_bih</code> using using from the view the view <code>pView</code> the  width, height,
24 bit/color, and BRG. It makes sure that the width and height are both multiple of 4.</p>

<pre>void SetBitmapHeader(LPBITMAPINFOHEADER lpbih);
</pre>	
<p><code>SetBitmapHeader</code> sets the bitmap info as in lpbih.  It supposes that the
user knows what he's doing.</p>

<pre>LPBITMAPINFOHEADER GetBitmapHeader()
</pre>
<p><code>GetBitmapHeader</code> returns a pointer to bitmap info header structure.</p>


<h3>AVI creation Functions</h3>
<pre>HRESULT InitEngine();
</pre>
<p><code>InitEngine</code> 
initializes the VFW engine and chooses a codec. This function has to be
called before starting to grab frames. Some asserts are 
made to check that bitmap info has been properly initialized.
It returns the last HRESULT. If something fails,
the error message can be retreived using GetLastErrorMessage().
<pre>
CAviGenerator avi;
HRESULT hr;

hr=avi.InitEngine();
if (FAILED(hr))
{
    AfxMessageBox(avi.GetLastErrorMessage());
    ...
}
</pre>
</p>

<pre>HRESULT AddFrame(BYTE* bmBits);
</pre>
<p><code>AddFrame</code> adds a frame to the movie. The data pointed by 
<code>bmBits</code> should be compatible with the bitmap description
made by <code>SetBitmapHeader</code>. Typically with OpenGL, 
<code>bmBits</code> is the buffer read when using <code>glReadPixels</code>.
As for <code>InitEnginge</code>, it returns the HRESULT.</p>

<pre>void ReleaseEngine();</pre>
<p><code>ReleaseEngine</code> releases ressources allocated for movie and close the file.
</p>

<h2>Using CAVIGenerator</h2>

<p>You have to follow these steps:</p>

<ol>
<li>Set the file name (optional), frame rate (optional) and bitmap info (required). 
If you want to grab an OpenGL
screen, just send a pointer of the <code>CView</code> object to the 
<code>SetBitmapHeader</code> function. Alternative, the user can fill in the 
<code>BITMAPINFOHEADER</code> structure himself. Make sure that dimension of bitmap are
a multiple of 4.</li>

<li>Initialize the AVI engine calling <code>InitEngine</code>. A dialog box will
popup to choose and fill in the parameters of the codec.</li>

<li>For each frame: Do the drawing stuff, fill the image buffer with BRG ordering and send it to the AVI engine using <code>AddFrame</code>.</li>

<li>Release ressources and close file by calling <code>ReleaseEngine</code>.</li>

</ol>


<p>And you're are done! Here's some demo pseudo-code:</p>
<pre>	CAVIGenerator AviGen;	// generator
	BYTE* bmBits;	// image buffer
	HRESULT hr;

	AviGen.SetRate(20);	// set 20fps
	AviGen.SetBitmapHeader(GetActiveView());	// get bitmap info out of the view
	hr=AviGen.InitEngine()	// start engine
	if (FAILED(hr))
	{
	    AfxMessageBox(avi.GetLastErrorMessage());
	    goto Cleaning;
	}

	LPBITMAPINFOHEADER lpbih=AviGen.GetBitmapInfo(); // getting bitmap info
	bmBits=new BYTE[3 /* BRG*/ * lpbih-&gt;biWidth* lpbih-&gt;biHeight];	// allocating memory for bmBits
	for (int i=0;i&lt;100;i++)	// make 100 frames
	{
		// TODO pust your draw code here.	
		 /* Draw code where bmBits is filled. 
		 For example, to read OpenGL buffer, put 
		 glReadPixels(0,0,lpbih-&gt;biWidth,lpbih-&gt;biHeight,GL_BGR_EXT,GL_UNSIGNED_BYTE,bmBits); */ 

		// adding frame and continue if OK
		hr=AviGen.AddFrame(bmBits);
		if (FAILED(hr))
		{
		    AfxMessageBox(avi.GetLastErrorMessage());
		    goto Cleaning;
		}
	}
	
	// cleaning memory	
	Cleaning:
	AviGen.ReleaseEngine(); // releasing ressources
	delete[] bmBits;	// release ressources</pre>


<h2>Adding CAVIGenerator to your project</h2>

<ol>
<li>Add <i>AVIGenerator.h</i> and <i>AVIGenerator.cpp</i> to your project.</li>
</ol>

<h2>Non-MFC Applications</h2>
If you want to use CAviGenerator without MFC, undefine _AVIGENERATOR_MFC in AviGenerator.h. It will disable MFC function calls.

<h2>Demo project</h2>

<p>A simple MFC SDI application that shows a cube and triangle rotating using OpenGL.
When selecting the menu item Avi Generation-&gt;Generate..., you start
to create a 100 frames AVI movie.</p>

<p>OpenGL drawing code is copy-pasted from lesson 5 of 
<a href="http://nehe.gamedev.net/">NeHe Productions</a>.</p>


<h2>Update History</h2>

<ul>
<li><b>21.10.2002</b> Ported to non-MFC application, added HRESULT handling</li>
<li><b>11.8.2001</b> Other bug fixed. Thanks to Dick W Augustsson.</li>
<li><b>11.2.2001</b> Bug fixed in setting bitmap header biSizeImage field. Thanks to David.</li>
<li><b>10.8.2001</b> Bug fixed in <code>~CAviGenerator</code> and in example above (<code>LPBITMAPINFOHEADER lpbih</code> not initialized).</li>
<li><b>10.5.2001</b> Bug fixed in <code>CAVIGenerator::SetBitmapHeader(LPBITMAPINFOHEADER lpbih)</code> function. Thanks to Lori Gardi.</li>
</ul>









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