Basename:    ?? please check the spelling for me!
Title:       HOWTO play and record sound
Author:      Thomas.Holme 
Email:       thomas.holme@openmpeg4.org
Environment: VC++ 6.0, win2k
Keywords:    mmsystem, sound, play, record
Level:       Beginner
Description: Howto record and play sound
Section      Multimedia
SubSection   Audio

• Download source + demo 200 Kb



Introduction

This is a simple application that show you how to play and record sound under windows.
It uses the old multimedia API. A better solution may be to use DirectSound.



HOWTO read the code fast

Start with the two functions in CFisterDlg called OnPlay and OnRecord. Follow them down to the depth you need to use the classes.

Short description

CSoundIn is a wrapper class that will let you retreive sound from the soundcard. Main functions is Start() and Stop()

CSoundOut is a wrapper class that will let you play sound on the soundcard. Main functions is Start() and Stop()

CSoundFile is a wrapper class of a single wave file, it can either be a file reader or a file writer object. See the constructor.

CSoundBase is a very small class that encapsulate the wave format.

CBuffer is a very small class that encapsulates a simple one dimentional buffer.

The project has a number of different callback functions:

• One callback function make the Play button change it's lable to stop when it has finished playing the file. CDialogDlg enherits CPipe and overload a function that CPipe can call when it has finished playing the wave file.
• Another callback function make it possible for CSoundIn to callback to CPipe when it has filled the input buffer. Thus CPipe can give CSoundIn a new buffer to fill.
• A clone of the above principle is also used in CSoundOut, which enables it to callback to the owner when it is finished playing the sound in a given buffer.

Problems that I encountered

I have spend almost 2 days debugging the following stupid problem. When CSoundIn and CSoundOut inherit from CSoundBase and CWinThread the order in which they are listed MUST be as shown below. If not the callback functions, which are started by the WinThread message handler, will not be able to access the member variables of the CSoundIn object.

class CSoundIn : public CWinThread, public CSoundBase

During these two days of fustration I also tried to implement the callback as regular callback functions called by the device driver. This is possible using ::waveInOpen(...). But since the this callback function is not allowed to call any of the ::waveInXXX(...) functions it is not of much use.