Iphone 音频总结

http://www.cnblogs.com/qq78292959/archive/2011/05/25/2076622.html

今天自己总结一下工程里的实现一个在线的音频播放器。。。

第一步呢。。先初始化AudioSession。为了实现中断的控制和后台，锁屏的播放状态

- (id)initsession {

AudioSessionInitialize (NULL, NULL, interruptionListenerCallback, self);

UInt32 sessionCategory = kAudioSessionCategory_MediaPlayback;//采用后台和锁屏时仍继续播放的模式;

AudioSessionSetProperty (kAudioSessionProperty_AudioCategory, sizeof (sessionCategory), &sessionCategory);

UInt32 doSetProperty = 0;

AudioSessionSetProperty (kAudioSessionProperty_OverrideCategoryMixWithOthers,sizeof (doSetProperty),&doSetProperty);

AudioSessionSetActive (true);//激活AudioSession

return self;

}

void interruptionListenerCallback (void *inUserData, UInt32 interruptionState) {

AudioPlayer *player = (AudioPlayer*)inUserData;

if (interruptionState == kAudioSessionBeginInterruption) {

//使音乐暂停

AudioWrapper * ad = [AudioWrapper sharedAudioWrapperElement];

[ad pause];

}

else if (interruptionState == kAudioSessionEndInterruption ) {

OSStatus rc = AudioSessionSetActive(true);

if (rc) {

NSLog(@"AudioSessionSetActive(true) returned %d", rc);

}

//使音乐恢复播放

AudioWrapper * ad = [AudioWrapper sharedAudioWrapperElement];

[ad resume];

}

}

第二步呢。。。为了接受在线过来的数据要使用媒体流功能，设置，最后解析NSData成为音频Buffer数据。。

先打开流媒体功能：

error = AudioFileStreamOpen(

(void*)self,

&AudioFileStreamPropertyListenerProc, //监听设置变化

&AudioFileStreamPacketsProc, //数据解析后的接收函数

0,

&audio_file_stream);//媒体流的ID

void AudioFileStreamPropertyListenerProc(

void *inClientData,

AudioFileStreamID inAudioFileStream,

AudioFileStreamPropertyID inPropertyID,

UInt32 *ioFlags)

{

#ifdef KXT_DEBUG

[ZPub LogTalk:@"AudioFileStreamPropertyListenerProc"];

#endif

;

}

void AudioFileStreamPacketsProc(

void *inClientData,

UInt32 inNumberBytes,

UInt32 inNumberPackets,

const void *inInputData,

AudioStreamPacketDescription *inPacketDescriptions) {

[(AudioPlayer*)inClientData newAudioData:inInputData bytes:inNumberBytes packets:inNumberPackets packetDescriptions:inPacketDescriptions];//自己开始整理解析后的数据

}

然后再把NSData传给解码器解析：

error = AudioFileStreamParseBytes(

audio_file_stream,//在这时，媒体流文件ID被生成

datalen,

[data bytes],

kAudioFileStreamProperty_FileFormat);

这样解码后的数据自动会被发送到AudioFileStreamPacketsProc接口里。。

第三步;准备Buffer数据（mAudioData（所有的Data），mAudioDataByteSize数据的大小，num_packets多少包，packet_descriptions包的描述）

- (id)initWithData:(NSData*)_data packets:(UInt32)_num_packets packetDescriptions:(const AudioStreamPacketDescription*)_packet_descriptions {

if(!_data)

return nil;

if(!_packet_descriptions)

return nil;

self = [super init];

if(!self)

return nil;

self.data = _data;

num_packets = _num_packets;

packet_descriptions = malloc(num_packets * sizeof(AudioStreamPacketDescription));

memcpy((void*)packet_descriptions, (const void*)_packet_descriptions, num_packets * sizeof(AudioStreamPacketDescription));

return self;

}

第四步如果没有播放队列就创建播放队列。。。

UInt32 formatListSize;

Boolean b;//拿媒体流文件ID申请它的音乐格式结构信息

AudioFileStreamGetPropertyInfo(audio_file_stream,

kAudioFileStreamProperty_FormatList,

&formatListSize,

&b);

// now get the format data得到音乐格式信息

NSMutableData *listData = [NSMutableData dataWithLength:formatListSize];

OSStatus status = AudioFileStreamGetProperty(audio_file_stream,

kAudioFileStreamProperty_FormatList,

&formatListSize,

[listData mutableBytes]);

AudioFormatListItem *formatList = [listData mutableBytes];

// The formatList property isn't always supported, so an error isn't unexpected here.

// Therefore, we won't call VERIFY_STATUS on this status code.

if (status == noErr) {

// now see which format this device supports best

UInt32 chosen;

UInt32 chosenSize = sizeof(UInt32);

int formatCount = formatListSize/sizeof(AudioFormatListItem);

status = AudioFormatGetProperty ('fpfl',

formatListSize,

formatList,

&chosenSize,

&chosen);

if (status == noErr) {

audio_format = formatList[chosen].mASBD;//获取到具体的音乐格式（用于创建更好的播放队列）

} else {

// the docs tell us to grab the last in the list because it's most compatible

audio_format = formatList[formatCount - 1].mASBD;

}

} else {

// fall back to the stream's DataFormat

UInt32 audio_format_size = sizeof(AudioStreamBasicDescription);

error = AudioFileStreamGetProperty(audio_file_stream,

kAudioFileStreamProperty_DataFormat,

&audio_format_size,

&audio_format);

if(error){

[buffer release];

return;

}

}

Float32 outValue ;

AudioQueueGetParameter(audio_queue,kAudioQueueDeviceProperty_NumberChannels,&outValue) ;

if(![self createAudioQueue]){

[buffer release];

return;

}

}

- (BOOL)createAudioQueue {

error = AudioQueueNewOutput(&audio_format, &MyAudioQueueOutputCallback, (void*)self, [[NSRunLoop currentRunLoop] getCFRunLoop], kCFRunLoopCommonModes, 0, &audio_queue);

}

最后。将准备好的buffer放到已创建的播放队列里就播放了。

[buffer enqueueOnQueue:audio_queue];

- (void)enqueueOnQueue:(AudioQueueRef)queue {

AudioQueueBufferRef buffer;

error = AudioQueueAllocateBuffer(queue, [data length], &buffer);

if(error) {

[super dealloc];

return;

}

buffer->mAudioDataByteSize = [data length];

memcpy((char*)buffer->mAudioData, [data bytes], [data length]);

error = AudioQueueEnqueueBuffer(queue, buffer, num_packets, packet_descriptions);

if(error) {

[ZPub LogTalk:[NSString stringWithFormat:@"AudioQueueEnqueueBuffer failed with %d", (int)error]];

return;

}

}