Question

I want to transcode a lot of audio from its source format to PCM without resampling or messing with the sample size. I figure if Windows Media Player can play the file and it doesn’t use a legacy ACM codecs it must be using DirectSound to do so (this is on Windows XP and Windows Server 2k3). So is it possible to access DirectSound from C# and do so? I’ve tried searching the web but all the examples have been about playback which I have no interest in doing.

Answer 1

DirectSound is an audio playback API, you mean DirectShow. Windows Media player does use DirectShow to play audio files. In theory, all you need to do is build the same playback graph that media player uses, but replace the audio driver on the end with a .WAV writer filter.

This is somewhat easier to do in C++ code, since the DirectShow graph object is really designed to be called from C++, but with a good set of interop definitions, you can do this in C#.

There’s http://directshownet.sourceforge.net/ for serious hacking with DirectShow in .NET, but that’s probably overkill for your problem.

I would suggest getting a copy of GraphEdit if you don’t already have one. You can use it to “prototype” direct show graphs interactively. drop a file into graphedit. then delete the filter on the end and replace it with a file writer filter.

One problem you will have is that there is no .WAV file writer filter in the default set of o DirectShow filters, you will have to find or write one.

If you just want to get the files converted, and could care less about learning how to write code using DirectShow, I would suggest that you just get a copy of Sound Forge (possibly even a demo version). It has a scripting language (C#,vb) that can be used to easily batch process most audio file formats.