Inside Macintosh: Sound /

Chapter 2 - Sound Manager / Sound Manager Reference

Sound Manager Routines / Playing Sound Resources

SndPlay

You can use the SndPlay function to play a sound resource that your application has loaded into memory.

FUNCTION SndPlay (chan: SndChannelPtr; sndHdl: Handle; 
                  async: Boolean): OSErr;

chan

A pointer to a valid sound channel. You can pass NIL instead of a pointer to a sound channel if you want the Sound Manager to internally allocate a sound channel in your application's heap zone.

sndHdl

A handle to the sound resource to play.

async

A Boolean value that indicates whether the sound should be played asynchronously (TRUE) or synchronously (FALSE). This parameter is ignored (and the sound plays synchronously) if NIL is passed in the first parameter.

DESCRIPTION

The SndPlay function attempts to play the sound located at sndHdl, which is expected to have the structure of a format 1 or format 2 'snd ' resource. If the resource has not yet been loaded, the SndPlay function fails and returns the resProblem result code.

All commands and data contained in the sound handle are then sent to the channel. Note that you can pass SndPlay a handle to some data created by calling the Sound Input Manager's SndRecord function as well as a handle to an actual 'snd ' resource that you have loaded into memory.

WARNING

In some versions of system software prior to system software version 7.0, the SndPlay function will not work properly with sound resources that specify the sound data type twice. This might happen if a resource specifies that a sound consists of sampled-sound data and an application does the same when creating a sound channel. For more information on this problem, see "Allocating Sound Channels" on page 2-20.

The chan parameter is a pointer to a sound channel. If chan is not NIL, it is used as a valid channel. If chan is NIL, an internally allocated sound channel is used. If you do supply a sound channel pointer in the chan parameter, you can play the sound asynchronously. When a sound is played asynchronously, a callback procedure can be called when a callBackCmd command is processed by the channel. (This procedure is the callback procedure supplied to SndNewChannel.) See "Playing Sounds Asynchronously" on page 2-46 for more information on playing sounds asynchronously. The handle you pass in the sndHdl parameter must be locked for as long as the sound is playing asynchronously.

If a format 1 'snd ' resource does not specify which type of sound data is to be played, SndPlay defaults to square-wave data. SndPlay also supports format 2 'snd ' resources using sampled-sound data and a bufferCmd command. Note that to use SndPlay and sampled-sound data with a format 1 'snd ' resource, the resource must include a bufferCmd command.

SPECIAL CONSIDERATIONS

Because the SndPlay function moves memory, you should not call it at interrupt time.

RESULT CODES

noErr	0	No error
notEnoughHardwareErr	-201	Insufficient hardware available
resProblem	-204	Problem loading the resource
badChannel	-205	Channel is corrupt or unusable
badFormat	-206	Resource is corrupt or unusable

SEE ALSO

For an example of how to play a sound resource using the SndPlay function, see the chapter "Introduction to Sound on the Macintosh" in this book.

For information on playing a sound resource without using the SndPlay function, see "Playing Sounds Using Low-Level Routines" on page 2-61.