Android音频数据传输.docx

MediaPlayer那边就不看了，从AudioTrack开始研究。1、AudioTrack::write函数调用函数obtainBuffer获取到一块buffer，然后把传入的数据copy到获取的buffer中。2、AudioTrack::obtainBuffer函数该函数的主要功能就是对传入的audioBuffer进行赋值。看看audioBuffer的类型：class Buffer { public: enum { MUTE ? ?= 0}; uint32_t ? ?flags; int ? ? ? ? channelCount; int ? ? ? ? format; size_t ? ? ?frameCount; size_t ? ? ?size; union { void* ? ? ? raw; short* ? ? ?i16; int8_t* ? ? i8; }; };其中存放数据的是下面这个东东：union { void* ? ? ? raw; short* ? ? ?i16; int8_t* ? ? i8; };对这块东东赋值的代码如下：audioBuffer-raw = (int8_t *)cblk-buffer(u);先看其中cblk的来历：audio_track_cblk_t* cblk = mCblk;mCblk的赋值在函数AudioTrack::createTrack中：mCblk = static_castaudio_track_cblk_t*(cblk-pointer());cblk的由来：spIMemory cblk = track-getCblk();track的由来： spIAudioTrack track = audioFlinger-createTrack(getpid(), streamType, sampleRate, format, channelCount, frameCount, ((uint16_t)flags) 16, sharedBuffer, output, mSessionId, status);?函数AudioFlinger::createTrack返回的是一个TrackHandle对象：trackHandle = new TrackHandle(track);return trackHandle;track的由来： track = thread-createTrack_l(client, streamType, sampleRate, format, channelCount, frameCount, sharedBuffer, lSessionId, lStatus);函数AudioFlinger::PlaybackThread::createTrack_l返回的是一个Track对象： track = new Track(this, client, streamType, sampleRate, format, channelCount, frameCount, sharedBuffer, sessionId); return track;看看函数TrackHandle::getCblk() ：return mTrack-getCblk();mTrack就是作为构造函数传入的track对象。函数AudioFlinger::ThreadBase::TrackBase::getCblk() 的实现：return mCblkMemory;mCblkMemory的赋值在构造函数AudioFlinger::ThreadBase::TrackBase::TrackBase中：mCblkMemory = client-heap()-allocate(size);mCblk = static_castaudio_track_cblk_t *(mCblkMemory-pointer()); // 这个成员变量也很重要client是构造函数参数：const spClient client函数AudioFlinger::Client::heap：return mMemoryDealer;mMemoryDealer的赋值在函数AudioFlinger::Client::Client中：mMemoryDealer(new MemoryDealer(1024*1024, AudioFlinger::Client))看看函数MemoryDealer::allocate：spIMemory MemoryDealer::allocate(size_t size){ spIMemory memory;// allocator()直接返回mAllocator// mAlloca