private static IntPtr GetCompressor(VfwApi.BitmapInfoHeader inBitmapInfo, VfwApi.BitmapInfoHeader outBitmapInfo, out VfwApi.CompressorInfo compressorInfo)
{
// Using ICLocate is time-consuming. Besides, it does not clean up something, so the process does not terminate on exit.
// Instead open a specific codec and query it for needed features.
var compressorHandle = VfwApi.ICOpen((uint)KnownFourCCs.CodecTypes.Video, outBitmapInfo.Compression, VfwApi.ICMODE_COMPRESS);
if (compressorHandle != IntPtr.Zero)
{
var inHeader = inBitmapInfo;
var outHeader = outBitmapInfo;
var result = VfwApi.ICSendMessage(compressorHandle, VfwApi.ICM_COMPRESS_QUERY, ref inHeader, ref outHeader);
if (result == VfwApi.ICERR_OK)
{
var infoSize = VfwApi.ICGetInfo(compressorHandle, out compressorInfo, Marshal.SizeOf(typeof(VfwApi.CompressorInfo)));
if (infoSize > 0 && compressorInfo.SupportsFastTemporalCompression)
{
return(compressorHandle);
}
}
VfwApi.ICClose(compressorHandle);
}
compressorInfo = new VfwApi.CompressorInfo();
return(IntPtr.Zero);
}
/// <summary>
/// Releases all unmanaged resources used by the encoder.
/// </summary>
public void Dispose()
{
if (!isDisposed)
{
if (needEnd)
{
EndCompression();
}
if (compressorHandle != IntPtr.Zero)
{
VfwApi.ICClose(compressorHandle);
}
isDisposed = true;
GC.SuppressFinalize(this);
}
}
/// <summary>
/// Gets info about the supported codecs that are installed on the system.
/// </summary>
public static CodecInfo[] GetAvailableCodecs()
{
var result = new List <CodecInfo>();
var inBitmapInfo = CreateBitmapInfo(8, 8, 32, KnownFourCCs.Codecs.Uncompressed);
inBitmapInfo.ImageSize = (uint)4;
foreach (var codec in DefaultCodecPreference)
{
var outBitmapInfo = CreateBitmapInfo(8, 8, 24, codec);
VfwApi.CompressorInfo compressorInfo;
var compressorHandle = GetCompressor(inBitmapInfo, outBitmapInfo, out compressorInfo);
if (compressorHandle != IntPtr.Zero)
{
VfwApi.ICClose(compressorHandle);
result.Add(new CodecInfo(codec, compressorInfo.Description));
}
}
return(result.ToArray());
}