Determining Features of Synthesizers
You can determine certain information about the capabilities of a synthesizer
by using the SndControl function. For example, you can determine whether a particular synthesizer supports a particular initialization option (some
synthesizers do not support all initialization options). This can be most useful
if you want your application to run under the enhanced Sound Manager as well as under earlier versions where the playback synthesizers do not have the
same output characteristics. By first determining whether the intended
synthesizer supports the desired output characteristics, you can avoid
requesting characteristics that are not available. Because you generally need to
know about the capabilities of a synthesizer before you actually create a sound
channel, you can call SndControl even if no channel has been created for the synthesizer.
To determine whether an initialization option is supported by a particular
synthesizer, call the SndControl function and pass it the availableCmd command. The following code example illustrates how to determine if the
sampled sound synthesizer supports stereo sound output.
Using the availableCmd command to check for stereo sound // Assuming inclusion of MacHeaders
#include <Sound.h>
// Prototype your routine like this prior to calling it
Boolean StereoAvailable (void);
Boolean StereoAvailable()
{
// Prototype for DoError function
mySndCmd.cmd = availableCmd;
mySndCmd. param1 = 0; [TOKEN:12079] unused on input
mySndCmd. param2 = initStereo; // test for stereo
if ( myErr != noErr )
DoError( myErr);
return ( mySndCmd. param1 != 0);
}
The SndControl function requires two parameters. The first parameter indicates the resource ID of the synthesizer whose characteristics are to be
determined. The second parameter is a sound command. In the case illustrated,
the cmd field of that sound command is set to availableCmd. The param2 field of
the sound command contains the initialization parameter in question. (The
initialization parameters are discussed in the separate section entitled
unused on input. If SndControl returns successfully, then param1 contains 1 if the synthesizer has the requested characteristics and 0 otherwise.
To determine which version of a synthesizer is available, call the
SndControl function with the versionCmd command. Neither param1 nor param2 of the sound command passed to SndControl is used on input. If the function returns successfully, the version is returned in param2 of the sound
command. For example, version 2.0 of a synthesizer would be returned as
0x00020000. The following code example illustrates how to use the
versionCmd command.
// Assuming inclusion of MacHeaders
#include <Sound.h>
// Prototype routine to get version like this prior to calling it
void GetVersion(long *);
void GetVersion (long * version)
{
OSErr myErr; // Error checking variable // Prototype for error handling procedure
void DoError(OSErr);
mySndCmd.cmd = versionCmd;
mySndCmd. param1 = 0; // unused on input
mySndCmd. param2 = 0; // unused on input
// determine version of sampled sound synthesizer
if ( myErr )
DoError( myErr);
else
*version = mySndCmd. param2;
}