What I would like to do is to pass an arbitrary audio file to a DirectShow filtergraph and receive a (PCM audio) stream object in the end using .NET 3.5 C# and DirectShow.NET. I would like to reach the point that I can just say:
Stream OpenFile(string filename) {...}
and
stream.Read(...)
I have been reading up on DirectShow for a couple of days and think I have started to grasp the idea of filters and filtergraphs. I found examples (to file / to device) how to play audio or write it to a file, but cannot seem to find the solution for a Stream object. Is this even possible? Could you point me in the right direction in case I missed something, please?
Best,
Hauke
I would like to share my solution to my own problem with you (my focus was on the exotic bwf file format. hence the name.):
using System;
using System.Collections.Generic;
using System.Text;
using DirectShowLib;
using System.Runtime.InteropServices;
using System.IO;
namespace ConvertBWF2WAV
{
public class BWF2WavConverter : ISampleGrabberCB
{
IFilterGraph2 gb = null;
ICaptureGraphBuilder2 icgb = null;
IBaseFilter ibfSrcFile = null;
DsROTEntry m_rot = null;
IMediaControl m_mediaCtrl = null;
ISampleGrabber sg = null;
public BWF2WavConverter()
{
// Initialize
int hr;
icgb = (ICaptureGraphBuilder2)new CaptureGraphBuilder2();
gb = (IFilterGraph2) new FilterGraph();
sg = (ISampleGrabber)new SampleGrabber();
#if DEBUG
m_rot = new DsROTEntry(gb);
#endif
hr = icgb.SetFiltergraph(gb);
DsError.ThrowExceptionForHR(hr);
}
public void reset()
{
gb = null;
icgb = null;
ibfSrcFile = null;
m_rot = null;
m_mediaCtrl = null;
}
public void convert(object obj)
{
string[] pair = obj as string[];
string srcfile = pair[0];
string targetfile = pair[1];
int hr;
ibfSrcFile = (IBaseFilter)new AsyncReader();
hr = gb.AddFilter(ibfSrcFile, "Reader");
DsError.ThrowExceptionForHR(hr);
IFileSourceFilter ifileSource = (IFileSourceFilter)ibfSrcFile;
hr = ifileSource.Load(srcfile, null);
DsError.ThrowExceptionForHR(hr);
// the guid is the one from ffdshow
Type fftype = Type.GetTypeFromCLSID(new Guid("0F40E1E5-4F79-4988-B1A9-CC98794E6B55"));
object ffdshow = Activator.CreateInstance(fftype);
hr = gb.AddFilter((IBaseFilter)ffdshow, "ffdshow");
DsError.ThrowExceptionForHR(hr);
// the guid is the one from the WAV Dest sample in the SDK
Type type = Type.GetTypeFromCLSID(new Guid("3C78B8E2-6C4D-11d1-ADE2-0000F8754B99"));
object wavedest = Activator.CreateInstance(type);
hr = gb.AddFilter((IBaseFilter)wavedest, "WAV Dest");
DsError.ThrowExceptionForHR(hr);
// manually tell the graph builder to try to hook up the pin that is left
IPin pWaveDestOut = null;
hr = icgb.FindPin(wavedest, PinDirection.Output, null, null, true, 0, out pWaveDestOut);
DsError.ThrowExceptionForHR(hr);
// render step 1
hr = icgb.RenderStream(null, null, ibfSrcFile, (IBaseFilter)ffdshow, (IBaseFilter)wavedest);
DsError.ThrowExceptionForHR(hr);
// Configure the sample grabber
IBaseFilter baseGrabFlt = sg as IBaseFilter;
ConfigSampleGrabber(sg);
IPin pGrabberIn = DsFindPin.ByDirection(baseGrabFlt, PinDirection.Input, 0);
IPin pGrabberOut = DsFindPin.ByDirection(baseGrabFlt, PinDirection.Output, 0);
hr = gb.AddFilter((IBaseFilter)sg, "SampleGrabber");
DsError.ThrowExceptionForHR(hr);
AMMediaType mediatype = new AMMediaType();
sg.GetConnectedMediaType(mediatype);
hr = gb.Connect(pWaveDestOut, pGrabberIn);
DsError.ThrowExceptionForHR(hr);
// file writer
FileWriter file_writer = new FileWriter();
IFileSinkFilter fs = (IFileSinkFilter)file_writer;
fs.SetFileName(targetfile, null);
hr = gb.AddFilter((DirectShowLib.IBaseFilter)file_writer, "File Writer");
DsError.ThrowExceptionForHR(hr);
// render step 2
AMMediaType mediatype2 = new AMMediaType();
pWaveDestOut.ConnectionMediaType(mediatype2);
gb.Render(pGrabberOut);
// alternatively to the file writer use the NullRenderer() to just discard the rest
// assign control
m_mediaCtrl = gb as IMediaControl;
// run
hr = m_mediaCtrl.Run();
DsError.ThrowExceptionForHR(hr);
}
//
// configure the SampleGrabber filter of the graph
//
void ConfigSampleGrabber(ISampleGrabber sampGrabber)
{
AMMediaType media;
// set the media type. works with "stream" somehow...
media = new AMMediaType();
media.majorType = MediaType.Stream;
//media.subType = MediaSubType.WAVE;
//media.formatType = FormatType.WaveEx;
// that's the call to the ISampleGrabber interface
sg.SetMediaType(media);
DsUtils.FreeAMMediaType(media);
media = null;
// set BufferCB as the desired Callback function
sg.SetCallback(this, 1);
}
public int SampleCB(double a, IMediaSample b)
{
return 0;
}
/// <summary>
/// Called on each SampleGrabber hit.
/// </summary>
/// <param name="SampleTime">Starting time of the sample, in seconds.</param>
/// <param name="pBuffer">Pointer to a buffer that contains the sample data.</param>
/// <param name="BufferLen">Length of the buffer pointed to by pBuffer, in bytes.</param>
/// <returns></returns>
public int BufferCB(double SampleTime, IntPtr pBuffer, int BufferLen)
{
byte[] buffer = new byte[BufferLen];
Marshal.Copy(pBuffer, buffer, 0, BufferLen);
using (BinaryWriter binWriter = new BinaryWriter(File.Open(@"C:\directshowoutput.pcm", FileMode.Append)))
{
binWriter.Write(buffer);
}
return 0;
}
}
}
This (AVILibrary Wrapper) may lead you to a solution, it's not DirectSound based (which I get the feeling is very much biased to interfacing your code with the playback hardware) but could be the answer.
Another approach can be found here.
How about NAudio ? http://www.codeplex.com/naudio It has a stream implementation.
来源：https://stackoverflow.com/questions/857546/how-to-access-an-audio-stream-using-directshow-net-c-sharp