我的应用程序从查找表中合成音频。它成功播放音频，但在我尝试停止播放时崩溃。音频播放只需退出而不重新启动，因此处理中断的要求是基本的。我重读了Apple的音频会话编程指南，包括Responding to Interruptions部分。然而，方法handleAudioSessionInterruption似乎没有注册中断，所以我显然错过了一些东西。
编辑查看我的回答。当我开始研究这个时，我对NSNotificationCenter几乎一无所知，所以我欢迎任何有待改进的建议。
两种方法设置音频会话在前台播放。
- (void)setUpAudio
{
if (_playQueue == NULL)
{
if ([self setUpAudioSession] == TRUE)
{
[self setUpPlayQueue];
[self setUpPlayQueueBuffers];
}
}
}
- (BOOL)setUpAudioSession
{
BOOL success = NO;
NSError *audioSessionError = nil;
AVAudioSession *session = [AVAudioSession sharedInstance];
// Set up notifications
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(handleAudioSessionInterruption:)
name:AVAudioSessionInterruptionNotification
object:session];
// Set category
success = [session setCategory:AVAudioSessionCategoryPlayback
error:&audioSessionError];
if (!success)
{
NSLog(@"%@ Error setting category: %@",
NSStringFromSelector(_cmd), [audioSessionError localizedDescription]);
// Exit early
return success;
}
// Set mode
success = [session setMode:AVAudioSessionModeDefault
error:&audioSessionError];
if (!success)
{
NSLog(@"%@ Error setting mode: %@",
NSStringFromSelector(_cmd), [audioSessionError localizedDescription]);
// Exit early
return success;
}
// Set some preferred values
NSTimeInterval bufferDuration = .005; // I would prefer a 5ms buffer duration
success = [session setPreferredIOBufferDuration:bufferDuration
error:&audioSessionError];
if (audioSessionError)
{
NSLog(@"Error %ld, %@ %i", (long)audioSessionError.code, audioSessionError.localizedDescription, success);
}
double sampleRate = _audioFormat.mSampleRate; // I would prefer a sample rate of 44.1kHz
success = [session setPreferredSampleRate:sampleRate
error:&audioSessionError];
if (audioSessionError)
{
NSLog(@"Error %ld, %@ %i", (long)audioSessionError.code, audioSessionError.localizedDescription, success);
}
success = [session setActive:YES
error:&audioSessionError];
if (!success)
{
NSLog(@"%@ Error activating %@",
NSStringFromSelector(_cmd), [audioSessionError localizedDescription]);
}
// Get current values
sampleRate = session.sampleRate;
bufferDuration = session.IOBufferDuration;
NSLog(@"Sample Rate:%0.0fHz I/O Buffer Duration:%f", sampleRate, bufferDuration);
return success;
}
这是按下停止按钮时处理中断的方法。但它没有回应。
编辑正确的方法需要block,而非selector.请参阅我的回答。
- (void)handleAudioSessionInterruption:(NSNotification*)notification
{
if (_playQueue)
{
NSNumber *interruptionType = [[notification userInfo] objectForKey:AVAudioSessionInterruptionTypeKey];
NSNumber *interruptionOption = [[notification userInfo] objectForKey:AVAudioSessionInterruptionOptionKey];
NSLog(@"in-app Audio playback will be stopped by %@ %lu", notification.name, (unsigned long)interruptionType.unsignedIntegerValue);
switch (interruptionType.unsignedIntegerValue)
{
case AVAudioSessionInterruptionTypeBegan:
{
if (interruptionOption.unsignedIntegerValue == AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation)
{
NSLog(@"notify other apps that audio is now available");
}
}
break;
default:
break;
}
}
}
答案 0 :(得分：0)
回答我处理AudioSessionInterruption的方法未正确使用observer订阅NSNotificationCentre。通过使用observer而不是block,
selector.来解决此问题
该解决方案取代了AVAudioSession delegate中已弃用的AudioBufferPlayer,方法，这种方法非常适合用于Matthias Hollejmans最初为直接音频合成开发的音频播放器。一些已弃用的功能（包括InterruptionListenerCallback）后来被Mario Diana升级。解决方案（以下）使用NSNotification，允许用户通过按下按钮优雅地退出AVAudioSession。
以下是相关代码。
<强> PlayViewController.m
UIButton操作会有序关闭synth，使timer无效，并发布将退出AVAudioSession的通知
- (void)fromEscButton:(UIButton*)button
{
[self stopConcertClock];
... // code for Exit PlayViewController not shown
}
- (void)stopConcertClock
{
[_synthLock lock];
[_synth stopAllNotes];
[_synthLock unlock];
[timer invalidate];
timer = nil;
[self postAVAudioSessionInterruptionNotification];
NSLog(@"Esc button pressed or sequence ended. Exit PlayViewController ");
}
- (void) postAVAudioSessionInterruptionNotification
{
[[NSNotificationCenter defaultCenter]
postNotificationName:@"AVAudioSessionInterruptionNotification"
object:self];
}
初始化AVAudioSession包括在startAudioPlayer
AudioBufferPlayer之前订阅单个中断通知
- (id)init
{
if (self = [super init])
{
NSLog(@"PlayViewController starts MotionListener and AudioSession");
[self startAudioSession];
}
return self;
}
- (void)startAudioSession
{
// Synth and the AudioBufferPlayer must use the same sample rate.
_synthLock = [[NSLock alloc] init];
float sampleRate = 44100.0f;
// Initialise synth to fill the audio buffer with audio samples.
_synth = [[Synth alloc] initWithSampleRate:sampleRate];
// Initialise the audio buffer.
_player = [[AudioBufferPlayer alloc] initWithSampleRate:sampleRate
channels:1
bitsPerChannel:16
packetsPerBuffer:1024];
_player.gain = 0.9f;
__block __weak PlayViewController *weakSelf = self;
_player.block = ^(AudioQueueBufferRef buffer, AudioStreamBasicDescription audioFormat)
{
PlayViewController *blockSelf = weakSelf;
if (blockSelf != nil)
{
// Lock access to the synth. This callback runs on an internal Audio Queue thread and we don't
// want another thread to change the Synth's state while we're still filling up the audio buffer.
[blockSelf -> _synthLock lock];
// Calculate how many packets fit into this buffer. Remember that a packet equals one frame
// because we are dealing with uncompressed audio; a frame is a set of left+right samples
// for stereo sound, or a single sample for mono sound. Each sample consists of one or more
// bytes. So for 16-bit mono sound, each packet is 2 bytes. For stereo it would be 4 bytes.
int packetsPerBuffer = buffer -> mAudioDataBytesCapacity / audioFormat.mBytesPerPacket;
// Let the Synth write into the buffer. The Synth just knows how to fill up buffers
// in a particular format and does not care where they come from.
int packetsWritten = [blockSelf -> _synth fillBuffer:buffer->mAudioData frames:packetsPerBuffer];
// We have to tell the buffer how many bytes we wrote into it.
buffer -> mAudioDataByteSize = packetsWritten * audioFormat.mBytesPerPacket;
[blockSelf -> _synthLock unlock];
}
};
// Set up notifications
[self subscribeForBlockNotification];
[_player startAudioPlayer];
}
- (void)subscribeForBlockNotification
{
NSNotificationCenter * __weak center = [NSNotificationCenter defaultCenter];
id __block token = [center addObserverForName:@"AVAudioSessionInterruptionNotification"
object:nil
queue:[NSOperationQueue mainQueue]
usingBlock:^(NSNotification *note) {
NSLog(@"Received the notification!");
[_player stopAudioPlayer];
[center removeObserver:token];
}];
}
<强> PlayViewController.h
这些是相关的界面设置
@interface PlayViewController : UIViewController <EscButtonDelegate>
{
...
// Initialisation of audio player and synth
AudioBufferPlayer* player;
Synth* synth;
NSLock* synthLock;
}
...
- (AudioBufferPlayer*)player;
- (Synth*)synth;
@end
<强> AudioBufferPlayer.m
- (void)stopAudioPlayer
{
[self stopPlayQueue];
[self tearDownPlayQueue];
[self tearDownAudioSession];
}
- (void)stopPlayQueue
{
if (_audioPlaybackQueue != NULL)
{
AudioQueuePause(_audioPlaybackQueue);
AudioQueueReset(_audioPlaybackQueue);
_playing = NO;
}
}
- (void)tearDownPlayQueue
{
AudioQueueDispose(_audioPlaybackQueue, NO);
_audioPlaybackQueue = NULL;
}
- (BOOL)tearDownAudioSession
{
NSError *deactivationError = nil;
BOOL success = [[AVAudioSession sharedInstance] setActive:NO
withOptions:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation
error:nil];
if (!success)
{
NSLog(@"%s AVAudioSession Error: %@", __FUNCTION__, deactivationError);
}
return success;
}