macOS Play Alert Sound
This article applies tomacOS only.
See also:Multiplatform Programming Guide
Overview
The Apple macOS operating system has many possible alert sounds which you can play to alert your user to various situation that need their attention. You can use System Sound Services to play short (30 seconds or shorter) sounds. The interface does not provide level, positioning, looping, or timing control, and does not support simultaneous playback: You can play only one sound at a time and the sound only plays once. You can, however, use System Sound Services to provide audible alerts.
System Sound Services supported audio formats:
- It only supports audio data formats linear PCM or IMA4.
- It only supports audio file formats CAF, AIF, or WAV.
If these limitations on System Sound Services are an issue, check out the AVFoundationAVAudioPlayer which does not suffer from the limitations.
Alert Sound Identifiers
These are the AudioToolbox identifiers for System Sound Services alert sounds and alternatives to sounds, for use with the AudioServicesPlayAlertSound:
| Identifier | Description |
|---|---|
| kSystemSoundID_Vibrate | On the iPhone, use this constant with the AudioServicesPlayAlertSound function to invoke a brief vibration. On the iPod touch, does nothing. |
| kSystemSoundID_UserPreferredAlert | On the desktop, use this constant with the AudioServicesPlayAlertSound function to play the alert specified in the Sound preference pane. |
| kSystemSoundID_FlashScreen | On the desktop, use this constant with the AudioServicesPlayAlertSound function to display a flash of light on the screen. |
| kUserPreferredAlert | Deprecated. Use kSystemSoundID_UserPreferredAlert instead. |
When a user has configured System Preferences to flash the screen for alerts, or if sound cannot be rendered, callingAudioServicesPlayAlertSound will result in the screen flashing. In macOS, pass the constantkSystemSoundID_UserPreferredAlert to play the alert sound selected by the user in System Preferences.
Result codes
This table lists the result codes defined for System Sound Services:
| Constant | Value | Description |
|---|---|---|
| kAudioServicesNoError | 0 | No error has occurred |
| kAudioServicesUnsupportedPropertyError | 'pty?' | The property is not supported |
| kAudioServicesBadPropertySizeError | '!siz' | The size of the property data was not correct |
| kAudioServicesBadSpecifierSizeError | '!spc' | The size of the specifier data was not correct |
| kAudioServicesSystemSoundUnspecifiedError | -1500 | An unspecified error has occurred |
| kAudioServicesSystemSoundClientTimedOutError | -1501 | System sound client message timed out |
Example code
The example application code below shows how to play those alert sounds. In this example the alert sound is being played by choosing a menu item which is just for the purposes of the demonstration.
Note that the choice of2 for the alert sound to play in this example is purely arbitrary. You should choose the number for the appropriate sound you want to play. Sound number 4096 is particularly interesting for deaf users. Try it :-)
Alternatively, you can use the sound identifier variables listed in the section above.
unitunit1;{$mode objfpc}{$H+}{$linkframework AudioToolbox}interfaceusesForms,Menus;type{ TForm1 }TForm1=class(TForm)MainMenu1:TMainMenu;MenuItem1:TMenuItem;procedureMenuItem1PlaySoundClick(Sender:TObject);MenuItem2:TMenuItem;procedureMenuItem2PlaySoundClick(Sender:TObject);privatepublicend;varForm1:TForm1;implementation{$R *.lfm}{ TForm1 }// Sound procedure declarationProcedureAudioServicesPlayAlertSound(inSystemSoundID:UInt32)externalname'_AudioServicesPlayAlertSound';// Menu item1 OnClick EventprocedureTForm1.MenuItem1PlaySoundClick(Sender:TObject);beginAudioServicesPlayAlertSound(2);// Use the appropriate value for the sound you wantend;// Menu item2 OnClick EventprocedureTForm1.MenuItem2PlaySoundClick(Sender:TObject);beginAudioServicesPlayAlertSound(kSystemSoundID_UserPreferredAlert);// Use the user's preferred alert soundend;end.
Playing an alert sound from a file
Not only can you play the existing operating system alert sounds, you can also play your own .wav sound files. The example application below demonstrates this. The Button1 OnClick event handler plays your sound from the specified file and updates the button caption with the SoundID assigned to the sound.
unitUnit1;{$mode objfpc}{$H+}{$modeswitch objectivec1}{$linkframework AudioToolbox}interface{$DEFINE DEBUG}// Comment if console log messages may requiredusesClasses,SysUtils,Forms,Controls,StdCtrls,Dialogs,{$IFDEF DEBUG}CocoaAll,{$ENDIF}MacOSAll;typeTSystemSoundID=UInt32;pSystemSoundID=^TSystemSoundID;{ TForm1 }TForm1=class(TForm)Button1:TButton;procedureButton1Click(Sender:TObject);privatepublicend;varForm1:TForm1;implementation{$R *.lfm}// Completion handler: Executed when the sound file finishes playingproceduremyCompletionHandler(SoundID:SystemSoundID;inClientData:CFStringRef);beginAudioServicesDisposeSystemSoundID(SoundID);// Dispose of a system sound object and associated resources{$IFDEF DEBUG}NSLog(NSStr('Completion handler called'));{$ENDIF}end;// System Sound Services procedure and function declarationsprocedureAudioServicesPlayAlertSound(inSystemSoundID:TSystemSoundID);externalname'_AudioServicesPlayAlertSound';functionAudioServicesCreateSystemSoundID(inFileURL:CFURLRef;outSystemSoundID:pSystemSoundID):OSStatus;externalname'_AudioServicesCreateSystemSoundID';functionAudioServicesAddSystemSoundCompletion(inSystemSoundID:TSystemSoundID;inRunLoop:CFRunLoopRef;inRunLoopMode:CFStringRef;inCompletionRoutine:Pointer;inClientData:CFURLRef):OSStatus;cdecl;externalname'AudioServicesAddSystemSoundCompletion';functionAudioServicesDisposeSystemSoundID(inSystemSoundID:TSystemSoundID):OSStatus;cdecl;externalname'_AudioServicesDisposeSystemSoundID';{ TForm1 }procedureTForm1.Button1Click(Sender:TObject);varnewSoundID:TSystemSoundID;filePathURL:CFURLRef;filePathCFStringRef:CFStringRef;filePathStr:String;status:Integer=-1;begin// Sound file to playfilePathStr:='/usr/local/share/fpcsrc/fpc-3.0.4/packages/libndsfpc/examples/audio/maxmod/basic_sound/audio/Ambulance.wav';filePathCFStringRef:=CFStringCreateWithPascalString(kCFAllocatorDefault,filePathStr,CFStringGetSystemEncoding);filePathURL:=CFURLCreateWithFileSystemPath(kCFAllocatorDefault,filePathCFStringRef,kCFURLPOSIXPathStyle,false);// Create a new system sound objectstatus:=AudioServicesCreateSystemSoundID(filePathURL,@newSoundID);if(status=kAudioServicesNoError)thenbeginButton1.Caption:=IntToStr(newSoundID);// Register a callback function, invoked when specified system sound finishes playingstatus:=AudioServicesAddSystemSoundCompletion(newSoundID,Nil,Nil,@myCompletionHandler,Nil);if(status<>kAudioServicesNoError)thenShowMessage('Error in AudioServicesAddSystemSoundCompletion() : '+IntToStr(status));// Play soundAudioServicesPlayAlertSound(newSoundID);endelseShowMessage('Error in AudioServicesCreateSystemSoundID() : '+IntToStr(status));end;end.
In the code above we are disposing of the system sound object and its associated resources in the completion handler procedure. You will not want to do this if you wish to replay the sound using it SoundID at a later time in the application (eg in a game).
