iOS音频播放 (二)：AudioSession

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[code]extern OSStatus AudioSessionInitialize(CFRunLoopRef inRunLoop,
                                       CFStringRef inRunLoopMode,
                                       AudioSessionInterruptionListener inInterruptionListener,
                                       void *inClientData);

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[code]typedef void (*AudioSessionInterruptionListener)(void * inClientData, UInt32 inInterruptionState);

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[code]extern OSStatus AudioSessionAddPropertyListener(AudioSessionPropertyID inID,
                                                AudioSessionPropertyListener inProc,
                                                void *inClientData);
                                              
typedef void (*AudioSessionPropertyListener)(void * inClientData,
                                             AudioSessionPropertyID inID,
                                             UInt32 inDataSize,
                                             const void * inData);

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[code]//AudioSession的AudioRouteChangeReason枚举
enum {
      kAudioSessionRouteChangeReason_Unknown = 0,
      kAudioSessionRouteChangeReason_NewDeviceAvailable = 1,
      kAudioSessionRouteChangeReason_OldDeviceUnavailable = 2,
      kAudioSessionRouteChangeReason_CategoryChange = 3,
      kAudioSessionRouteChangeReason_Override = 4,
      kAudioSessionRouteChangeReason_WakeFromSleep = 6,
      kAudioSessionRouteChangeReason_NoSuitableRouteForCategory = 7,
      kAudioSessionRouteChangeReason_RouteConfigurationChange = 8
  };

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[code]//***AudioSession的AudioRouteChangeReason枚举
typedef NS_ENUM(NSUInteger, ***AudioSessionRouteChangeReason)
{
  ***AudioSessionRouteChangeReasonUnknown = 0,
  ***AudioSessionRouteChangeReasonNewDeviceAvailable = 1,
  ***AudioSessionRouteChangeReasonOldDeviceUnavailable = 2,
  ***AudioSessionRouteChangeReasonCategoryChange = 3,
  ***AudioSessionRouteChangeReasonOverride = 4,
  ***AudioSessionRouteChangeReasonWakeFromSleep = 6,
  ***AudioSessionRouteChangeReasonNoSuitableRouteForCategory = 7,
  ***AudioSessionRouteChangeReasonRouteConfigurationChange NS_ENUM_***AILABLE_IOS(7_0) = 8
}

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[code]+ (BOOL)usingHeadset
{
#if TARGET_IPHONE_SIMULATOR
    return NO;
#endif

    CFStringRef route;
    UInt32 propertySize = sizeof(CFStringRef);
    AudioSessionGetProperty(kAudioSessionProperty_AudioRoute, &propertySize, &route);

    BOOL hasHeadset = NO;
    if((route == NULL) || (CFStringGetLength(route) == 0))
    {
        // Silent Mode
    }
    else
    {
        /* Known values of route:
         * "Headset"
         * "Headphone"
         * "Speaker"
         * "SpeakerAndMicrophone"
         * "HeadphonesAndMicrophone"
         * "HeadsetInOut"
         * "ReceiverAndMicrophone"
         * "Lineout"
         */
        NSString* routeStr = (__bridge NSString*)route;
        NSRange headphoneRange = [routeStr rangeOfString : @"Headphone"];
        NSRange headsetRange = [routeStr rangeOfString : @"Headset"];

        if (headphoneRange.location != NSNotFound)
        {
            hasHeadset = YES;
        }
        else if(headsetRange.location != NSNotFound)
        {
            hasHeadset = YES;
        }
    }

    if (route)
    {
        CFRelease(route);
    }

    return hasHeadset;
}

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[code]+ (BOOL)isAirplayActived
{
    CFDictionaryRef currentRouteDescriptionDictionary = nil;
    UInt32 dataSize = sizeof(currentRouteDescriptionDictionary);
    AudioSessionGetProperty(kAudioSessionProperty_AudioRouteDescription, &dataSize, ¤tRouteDescriptionDictionary);

    BOOL airplayActived = NO;
    if (currentRouteDescriptionDictionary)
    {
        CFArrayRef outputs = CFDictionaryGetValue(currentRouteDescriptionDictionary, kAudioSession_AudioRouteKey_Outputs);
        if(outputs != NULL && CFArrayGetCount(outputs) > 0)
        {
            CFDictionaryRef currentOutput = CFArrayGetValueAtIndex(outputs, 0);
            //Get the output type (will show airplay / hdmi etc
            CFStringRef outputType = CFDictionaryGetValue(currentOutput, kAudioSession_AudioRouteKey_Type);

            airplayActived = (CFStringCompare(outputType, kAudioSessionOutputRoute_AirPlay, 0) == kCFCompareEqualTo);
        }
        CFRelease(currentRouteDescriptionDictionary);
    }
    return airplayActived;
}

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[code]extern OSStatus AudioSessionSetProperty(AudioSessionPropertyID inID,
                                        UInt32 inDataSize,
                                        const void *inData);

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[code]UInt32 sessionCategory = kAudioSessionCategory_MediaPlayback;
AudioSessionSetProperty (kAudioSessionProperty_AudioCategory,
                         sizeof(sessionCategory),
                         &sessionCategory);

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[code]/* set session category */
- (BOOL)setCategory:(NSString *)category error:(NSError **)outError;
/* set session category with options */
- (BOOL)setCategory:(NSString *)category withOptions: (***AudioSessionCategoryOptions)options error:(NSError **)outError NS_***AILABLE_IOS(6_0);

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[code]//AudioSession的AudioSessionCategory枚举
enum {
      kAudioSessionCategory_AmbientSound               = 'ambi',
      kAudioSessionCategory_SoloAmbientSound           = 'solo',
      kAudioSessionCategory_MediaPlayback              = 'medi',
      kAudioSessionCategory_RecordAudio                = 'reca',
      kAudioSessionCategory_PlayAndRecord              = 'plar',
      kAudioSessionCategory_AudioProcessing            = 'proc'
  };

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[code]//AudioSession的AudioSessionCategory字符串
/*  Use this category for background sounds such as rain, car engine noise, etc.  
 Mixes with other music. */
***F_EXPORT NSString *const ***AudioSessionCategoryAmbient;
  
/*  Use this category for background sounds.  Other music will stop playing. */
***F_EXPORT NSString *const ***AudioSessionCategorySoloAmbient;

/* Use this category for music tracks.*/
***F_EXPORT NSString *const ***AudioSessionCategoryPlayback;

/*  Use this category when recording audio. */
***F_EXPORT NSString *const ***AudioSessionCategoryRecord;

/*  Use this category when recording and playing back audio. */
***F_EXPORT NSString *const ***AudioSessionCategoryPlayAndRecord;

/*  Use this category when using a hardware codec or signal processor while
 not playing or recording audio. */
***F_EXPORT NSString *const ***AudioSessionCategoryAudioProcessing;

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[code]//AudioSession的启动方法
extern OSStatus AudioSessionSetActive(Boolean active);
extern OSStatus AudioSessionSetActiveWithFlags(Boolean active, UInt32 inFlags);

//***AudioSession的启动方法
- (BOOL)setActive:(BOOL)active error:(NSError **)outError;
- (BOOL)setActive:(BOOL)active withFlags:(NSInteger)flags error:(NSError **)outError NS_DEPRECATED_IOS(4_0, 6_0);
- (BOOL)setActive:(BOOL)active withOptions:(***AudioSessionSetActiveOptions)options error:(NSError **)outError NS_***AILABLE_IOS(6_0);

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[code]#import <Endian.h>

NSString * OSStatusToString(OSStatus status)
{
    size_t len = sizeof(UInt32);
    long addr = (unsigned long)&status;
    char cstring[5];

    len = (status >> 24) == 0 ? len - 1 : len;
    len = (status >> 16) == 0 ? len - 1 : len;
    len = (status >>  8) == 0 ? len - 1 : len;
    len = (status >>  0) == 0 ? len - 1 : len;

    addr += (4 - len);

    status = EndianU32_NtoB(status);        // strings are big endian

    strncpy(cstring, (char *)addr, len);
    cstring[len] = 0;

    return [NSString stringWithCString:(char *)cstring encoding:NSMacOSRomanStringEncoding];
}

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[code]static void MyAudioSessionInterruptionListener(void *inClientData, UInt32 inInterruptionState)
{
    AudioSessionInterruptionType interruptionType = kAudioSessionInterruptionType_ShouldNotResume;
    UInt32 interruptionTypeSize = sizeof(interruptionType);
    AudioSessionGetProperty(kAudioSessionProperty_InterruptionType,
                            &interruptionTypeSize,
                            &interruptionType);

    NSDictionary *userInfo = @{MyAudioInterruptionStateKey:@(inInterruptionState),
                               MyAudioInterruptionTypeKey:@(interruptionType)};

    [[NSNotificationCenter defaultCenter] postNotificationName:MyAudioInterruptionNotification object:nil userInfo:userInfo];
}

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[code]- (void)interruptionNotificationReceived:(NSNotification *)notification
{
    UInt32 interruptionState = [notification.userInfo[MyAudioInterruptionStateKey] unsignedIntValue];
    AudioSessionInterruptionType interruptionType = [notification.userInfo[MyAudioInterruptionTypeKey] unsignedIntValue];
    [self handleAudioSessionInterruptionWithState:interruptionState type:interruptionType];
}

- (void)handleAudioSessionInterruptionWithState:(UInt32)interruptionState type:(AudioSessionInterruptionType)interruptionType
{
    if (interruptionState == kAudioSessionBeginInterruption)
    {
        //控制UI，暂停播放
    }
    else if (interruptionState == kAudioSessionEndInterruption)
    {
        if (interruptionType == kAudioSessionInterruptionType_ShouldResume)
        {
            OSStatus status = AudioSessionSetActive(true);
            if (status == noErr)
            {
                //控制UI，继续播放
            }
        }
    }
}