IOS Audio Unit播放MP3、AAC

示例代码： XBVoiceTool

所需基础：

Audio Unit播放PCM数据

分析：

前面讲过如何播放PCM数据，现在我们需要的就是把MP3或者AAC格式的数据转成PCM数据，提供给Player进行播放。

引入几个新的内容：

ExtAudioFileRef ：代表所读取的音频。可以用 ExtAudioFileOpenURL 创建
ExtAudioFileSetProperty ：设置 ExtAudioFileRef 的属性
ExtAudioFileRead ：从 ExtAudioFileRef 读取数据

关键代码：

1.读取音频

NSURL *url = [NSURL fileURLWithPath:filePath];
CheckError(ExtAudioFileOpenURL((__bridge CFURLRef)url, &_audioFile),"打开文件失败");

2.设置 _audioFile 转换出来的音频流格式信息（即从_audioFile读取到的音频流格式）

uint size = sizeof(_outputFormat);
CheckError(ExtAudioFileSetProperty(_audioFile, kExtAudioFileProperty_ClientDataFormat, size, &_outputFormat), "setkExtAudioFileProperty_ClientDataFormat failure");

3.调用ExtAudioFileRead ，从 _audioFile 读取数据,并赋值给Player

_player.bl_inputFull = ^(XBAudioUnitPlayer *player, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData) {
            strongSelf->_bufferList->mBuffers[0].mDataByteSize = CONST_BUFFER_SIZE;
            OSStatus status = ExtAudioFileRead(strongSelf->_audioFile, &inNumberFrames, strongSelf->_bufferList);
            memcpy(ioData->mBuffers[0].mData, strongSelf->_bufferList->mBuffers[0].mData, strongSelf->_bufferList->mBuffers[0].mDataByteSize);
            ioData->mBuffers[0].mDataByteSize = strongSelf->_bufferList->mBuffers[0].mDataByteSize;
            if (ioData->mBuffers[0].mDataByteSize == 0)
            {
                [weakSelf stop];
            }
            strongSelf->_readedFrame += ioData->mBuffers[0].mDataByteSize / strongSelf->_outputFormat.mBytesPerFrame;
            CheckError(status, "转换格式失败");
            if (inNumberFrames == 0) NSLog(@"播放结束");
            
            NSLog(@"%f",[strongSelf getProgress]);
        };