问题是在调用AudioOutputUnitStop暂停播放之后,在进入后台并返回到前台之后,在调用AudioOutputUnitStart之后,音频将不会再次启动.这是由于AVAssetReaderOutput的copyNextSampleBuffer方法返回的错误,它被称为渲染管道的一部分.

调用copyNextSampleBuffer之后,AVAssetReader的status属性为AVAssetReaderStatusFailed,其错误属性为Error Domain = AVFoundationErrorDomain Code = -11847“Operation Interrupted”UserInfo = 0x1d8b6100 {NSLocalizedRecoverySuggestion =停止其他操作,再次尝试,NSLocalizedDescription =操作中断}

我正在寻找一个解决方案,不会强制我重新初始化整个管道回到前台 – 希望有一个这样的解决方案,AVAssetReaders可以生存的应用程序到背景和背面…

笔记

>该应用程序有权在后台播放音频.
>我正在处理音频中断 – 将AVAudioSession设置为AVAudioSessionDelegates endInterruptionWithFlags：事件和应用程序激活时的活动.无论我是否做到这一点,没有什么不同,得到同样的错误.

一些代码：

AudioPlayer

@implementation AudioPlayer
    ...
// Audio Unit Setup
AudioComponentDescription desc;
desc.componentType = kAudioUnitType_Output;
desc.componentSubType = kAudioUnitSubType_RemoteIO;
desc.componentManufacturer = kAudioUnitManufacturer_Apple;
desc.componentFlags = 0;
desc.componentFlagsMask = 0;

AudioComponent defaultOutput = AudioComponentFindNext(NULL,&desc);

AudioComponentInstanceNew(defaultOutput,&_audioUnit);

AudioStreamBasicDescription audioFormat;
    FillOutASBDForLPCM(audioFormat,44100,2,16,false,false);

AudioUnitSetProperty(self.audioUnit,kAudioUnitProperty_StreamFormat,kAudioUnitScope_Input,kOutputBus,&audioFormat,sizeof(audioFormat));

AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = RenderCallback;
callbackStruct.inputProcRefCon = (__bridge void*)self;
AudioUnitSetProperty(self.audioUnit,kAudioUnitProperty_SetRenderCallback,&callbackStruct,sizeof(callbackStruct));

AudioUnitInitialize(self.audioUnit);

AudioReader设置

@implementation AudioReader
    ...
NSError* error = nil;
self.reader = [AVAssetReader assetReaderWithAsset:self.asset error:&error];
NSDictionary *outputSettings = ...
self.readerOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:[self.asset.tracks objectAtIndex:0] outputSettings:outputSettings];
[self.reader addOutput:self.readerOutput];
[self.reader startReading];

AudioReader渲染方法,最终由RenderCallback函数调用

-(BOOL)readChunkIntoBuffer
{
     CMSampleBufferRef sampleBuffer = [self.readerOutput copyNextSampleBuffer];
     if ( sampleBuffer == NULL )
     {
         NSLog(@"Couldn't copy next sample buffer,reader status=%d error=%@,self.reader.status,self.reader.error);
         return NO;
     }
 ...
}