DirectShow.NET

// Retrieve the stream control interface for the video device
// FindInterface will also add any required filters
// (WDM devices in particular may need additional
// upstream filters to function).

// Try looking for an interleaved media type
object o;
cat = PinCategory.Capture;
med = MediaType.Interleaved;
Guid iid = typeof(IAMStreamConfig).GUID;
hr = captureGraphBuilder.FindInterface(
    ref cat, ref med, videoDeviceFilter, ref iid, out o );

if ( hr != 0 )
{
    // If not found, try looking for a video media type
    med = MediaType.Video;
    hr = captureGraphBuilder.FindInterface(
        ref cat, ref med, videoDeviceFilter, ref iid, out o );

    if ( hr != 0 )
        o = null;
}
videoStreamConfig = (IAMStreamConfig) o;

// Retrieve the stream control interface for the audio device
o = null;
cat = PinCategory.Capture;
med = MediaType.Audio ;
iid = typeof(IAMStreamConfig).GUID;
hr = captureGraphBuilder.FindInterface(
    ref cat, ref med, audioDeviceFilter, ref iid, out o );
if ( hr != 0 )
    o = null;
audioStreamConfig = (IAMStreamConfig) o;

/// <summary>
///  Gets and sets the frame size used to capture video.
///  Not all frame size are supported. Changing to an unsupported
///  size will throw and exception. Not all devices support 
///  getting/setting the frame size, in which case, accessing 
///  this property will throw an exception.
/// </summary>
public Size FrameSize
{
	get
	{
		BitmapInfoHeader bmiHeader;
		bmiHeader = (BitmapInfoHeader) getStreamConfigSetting( videoStreamConfig, "BmiHeader" );
		Size size = new Size( bmiHeader.Width, bmiHeader.Height );
		return( size );
	}

	set
	{
		BitmapInfoHeader bmiHeader;
		bmiHeader = (BitmapInfoHeader) getStreamConfigSetting( videoStreamConfig, "BmiHeader" );
		bmiHeader.Width = value.Width;
		bmiHeader.Height = value.Height;
		setStreamConfigSetting( videoStreamConfig, "BmiHeader", bmiHeader );
	}		
}

/// <summary>
///  Get or set the audio sampling rate for waveform-audio data. 
///  Common sampling rates are 8.0 kHz, 11.025 kHz, 22.05 kHz, and 
///  44.1 kHz. Not all devices support getting/setting the 
///  sampling rate and not all sampling rates are supported, 
///  in which case, accessing this property will throw an 
///  exception.
/// </summary>
public int AudioSamplingRate
{
	get
	{
		int samplingRate = (int) getStreamConfigSetting( audioStreamConfig, "nSamplesPerSec" );
		return( samplingRate );
	}
	set
	{
		setStreamConfigSetting( audioStreamConfig, "nSamplesPerSec", value );
	}
}

/// <summary>
///  Retrieves the value of one member of the IAMStreamConfig format block.
///  Helper function for several properties that expose
///  video/audio settings from IAMStreamConfig.GetFormat().
///  IAMStreamConfig.GetFormat() returns a AMMediaType struct.
///  AMMediaType.formatPtr points to a format block structure.
///  This format block structure may be one of several
///  types, the type being determined by AMMediaType.formatType.
/// </summary>
protected object getStreamConfigSetting( IAMStreamConfig streamConfig, string fieldName)
{
    if ( streamConfig == null )
        throw new NotSupportedException();
    assertStateForProperty( CaptureState.Stopped );
    if ( isGraphRendered )
        derenderGraph();

    object returnValue = null;
    IntPtr pmt = IntPtr.Zero;
    AMMediaType mediaType = new AMMediaType();

    try
    {
        // Get the current format info
        int hr = streamConfig.GetFormat( out pmt );
        if ( hr != 0 )
            Marshal.ThrowExceptionForHR( hr );
        Marshal.PtrToStructure( pmt, mediaType );

        // The formatPtr member points to different structures
        // dependingon the formatType
        object formatStruct;
        if ( mediaType.formatType == FormatType.WaveEx )
            formatStruct = new WaveFormatEx();
        else if ( mediaType.formatType == FormatType.VideoInfo )
            formatStruct = new VideoInfoHeader();
        else
            throw new NotSupportedException( "This device does not support a recognized format block." );

        // Retrieve the nested structure
        Marshal.PtrToStructure( mediaType.formatPtr, formatStruct );

        // Find the required field
        Type structType = formatStruct.GetType();
        FieldInfo fieldInfo = structType.GetField( fieldName );
        if ( fieldInfo == null )
            throw new NotSupportedException( "Unable to find the member '" + fieldName + "' in the format block." );

        // Extract the field's current value
        returnValue = fieldInfo.GetValue( formatStruct );

    }
    finally
    {
        DsUtils.FreeAMMediaType( mediaType );
        Marshal.FreeCoTaskMem( pmt );
    }

    return( returnValue );
}

/// <summary>
///  Set the value of one member of the IAMStreamConfig format block.
///  Helper function for several properties that expose
///  video/audio settings from IAMStreamConfig.GetFormat().
///  IAMStreamConfig.GetFormat() returns a AMMediaType struct.
///  AMMediaType.formatPtr points to a format block structure.
///  This format block structure may be one of several
///  types, the type being determined by AMMediaType.formatType.
/// </summary>
protected object setStreamConfigSetting( IAMStreamConfig streamConfig, string fieldName, object newValue)
{
    if ( streamConfig == null )
        throw new NotSupportedException();
    assertStateForProperty( CaptureState.Stopped );
    if ( isGraphRendered )
        derenderGraph();

    object returnValue = null;
    IntPtr pmt = IntPtr.Zero;
    AMMediaType mediaType = new AMMediaType();

    try
    {
        // Get the current format info
        int hr = streamConfig.GetFormat( out pmt );
        if ( hr != 0 )
            Marshal.ThrowExceptionForHR( hr );
        Marshal.PtrToStructure( pmt, mediaType );

        // The formatPtr member points to different structures
        // dependingon the formatType
        object formatStruct;
        if ( mediaType.formatType == FormatType.WaveEx )
            formatStruct = new WaveFormatEx();
        else if ( mediaType.formatType == FormatType.VideoInfo )
            formatStruct = new VideoInfoHeader();
        else
            throw new NotSupportedException( "This device does not support a recognized format block." );

        // Retrieve the nested structure
        Marshal.PtrToStructure( mediaType.formatPtr, formatStruct );

        // Find the required field
        Type structType = formatStruct.GetType();
        FieldInfo fieldInfo = structType.GetField( fieldName );
        if ( fieldInfo == null )
            throw new NotSupportedException( "Unable to find the member '" + fieldName + "' in the format block." );

        // Update the value of the field
        fieldInfo.SetValue( formatStruct, newValue );

        // PtrToStructure copies the data so we need to copy it back
        Marshal.StructureToPtr( formatStruct, mediaType.formatPtr, false );

        // Save the changes
        hr = streamConfig.SetFormat( mediaType );
        if ( hr != 0 )
            Marshal.ThrowExceptionForHR( hr );

    }
    finally
    {
        DsUtils.FreeAMMediaType( mediaType );
        Marshal.FreeCoTaskMem( pmt );
    }

    return( returnValue );
}

/// <summary> 
///  Free the nested structures and release any 
///  COM objects within an AMMediaType struct.
/// </summary>
public static void FreeAMMediaType(AMMediaType mediaType)
{
	if ( mediaType.formatSize != 0 )
		Marshal.FreeCoTaskMem( mediaType.formatPtr );
	if ( mediaType.unkPtr != IntPtr.Zero ) 
		Marshal.Release( mediaType.unkPtr );
	mediaType.formatSize = 0;
	mediaType.formatPtr = IntPtr.Zero;
	mediaType.unkPtr = IntPtr.Zero;
}