Android MediaRecorder调用AudioRecord流程

  通过一个简单的api来看下调用流程，就看MediaRecorder类的setAudioChannels()设置通道数的方法.
废话不多说，直接来看流程.栗子：
MediaRecorder mRecorder = new MediaRecorder();
mRecorder.setAudioChannels(mChannels);1.frameworks/base/media/java/android/media/MediaRecorder.java
public void setAudioChannels(int numChannels) {setParameter("audio-param-number-of-channels=" + numChannels);
}private native void setParameter(String nameValuePair);2.frameworks/base/media/jni/android_media_MediaRecorder.cpp
static void android_media_MediaRecorder_setParameter(JNIEnv *env, jobject thiz, jstring params){sp<MediaRecorder> mr = getMediaRecorder(env, thiz);process_media_recorder_call(env, mr->setParameters(String8(params8)), "java/lang/RuntimeException", "setParameter failed.");
}3.
<1>.frameworks/av/include/media/mediarecorder.h
class MediaRecorder : public BnMediaRecorderClient, public virtual IMediaDeathNotifier{sp<IMediaRecorder> mMediaRecorder;
}<2>.frameworks/av/media/libmedia/mediarecorder.cpp
MediaRecorder::MediaRecorder(const String16& opPackageName) : mSurfaceMediaSource(NULL){const sp<IMediaPlayerService> service(getMediaPlayerService());mMediaRecorder = service->createMediaRecorder(opPackageName);
}status_t MediaRecorder::setParameters(const String8& params) {status_t ret = mMediaRecorder->setParameters(params);
}4.frameworks/av/media/libmedia/IMediaDeathNotifier.cpp
//Binder通信
<1>.const sp<IMediaPlayerService> IMediaDeathNotifier::getMediaPlayerService(){sMediaPlayerService == 0；sp<IServiceManager> sm = defaultServiceManager();sp<IBinder> binder;//此处为代理获取media.player对应的服务binder = sm->getService(String16("media.player"));sMediaPlayerService = interface_cast<IMediaPlayerService>(binder);
}<2>.frameworks/av/media/libmediaplayerservice/MediaPlayerService.cppvoid MediaPlayerService::instantiate() {//添加media.player字符串对应的MediaPlayerService服务defaultServiceManager()->addService(String16("media.player"), new MediaPlayerService());}
}<3>.frameworks/av/media/mediaserver/main_mediaserver.cpp
int main(int argc __unused, char **argv __unused){//启动MediaPlayerService服务MediaPlayerService::instantiate();ResourceManagerService::instantiate();//启动线程池ProcessState::self()->startThreadPool();//添加到线程池IPCThreadState::self()->joinThreadPool();
}<4>.frameworks/av/media/libmedia/mediarecorder.cpp
接着上边继续追service->createMediaRecorder()
MediaRecorder::MediaRecorder(const String16& opPackageName) : mSurfaceMediaSource(NULL){const sp<IMediaPlayerService> service(getMediaPlayerService());mMediaRecorder = service->createMediaRecorder(opPackageName);
}5.frameworks/av/media/libmediaplayerservice/MediaPlayerService.cpp
sp<IMediaRecorder> MediaPlayerService::createMediaRecorder(const String16 &opPackageName){sp<MediaRecorderClient> recorder = new MediaRecorderClient(this, pid, opPackageName);wp<MediaRecorderClient> w = recorder;mMediaRecorderClients.add(w);return recorder;
}6.frameworks/av/media/libmediaplayerservice/MediaRecorderClient.cpp
MediaRecorderClient::MediaRecorderClient(const sp<MediaPlayerService>& service, pid_t
pid, const String16& opPackageName){mRecorder = AVMediaServiceFactory::get()->createStagefrightRecorder(opPackageName);mMediaPlayerService = service;
}7.frameworks/av/media/libavextensions/mediaplayerservice/AVMediaServiceFactory.cpp
StagefrightRecorder *AVMediaServiceFactory::createStagefrightRecorder(const String16
&opPackageName) {return new StagefrightRecorder(opPackageName);
}8.frameworks/av/media/libmediaplayerservice/StagefrightRecorder.cpp
<1>.构造函数
StagefrightRecorder::StagefrightRecorder(const String16 &opPackageName): MediaRecorderBase(opPackageName),mWriter(NULL),  mOutputFd(-1), mAudioSource(AUDIO_SOURCE_CNT),mVideoSource(VIDEO_SOURCE_LIST_END),mStarted(false)
{ALOGV("Constructor");reset();
}注意：所以frameworks/av/media/libmedia/mediarecorder.cpp里的mMediaRecorder->setParameters(params);调用的是StagefrightRecorder.cpp里的
<2>.status_t StagefrightRecorder::setParameters(const String8 &params){const char *cparams = params.string();const char *key_start = cparams;String8 key(key_start, equal_pos - key_start);setParameter(key, value)；
}<3>.status_t StagefrightRecorder::setParameter(const String8 &key, const String8 &value)
{//由上文得出,走此分支else if (key == "audio-param-number-of-channels") {int32_t number_of_channels;if (safe_strtoi32(value.string(), &number_of_channels)) {return setParamAudioNumberOfChannels(number_of_channels);}}
}<4>.status_t StagefrightRecorder::setParamAudioNumberOfChannels(int32_t channels) {mAudioChannels = channels;//将mAudioChannels传出来
}<5>.sp<MediaCodecSource> StagefrightRecorder::createAudioSource() {sp<AudioSource> audioSource = AVFactory::get()->createAudioSource(mAudioSource,mOpPackageName,sourceSampleRate,mAudioChannels,mSampleRate,mClientUid,mClientPid);
}9.frameworks/av/media/libavextensions/stagefright/AVFactory.cpp
AudioSource* AVFactory::createAudioSource(audio_source_t inputSource,const String16 &opPackageName,uint32_t sampleRate,uint32_t channels,uint32_t outSampleRate,uid_t clientUid,pid_t clientPid) {return new AudioSource(inputSource, opPackageName, sampleRate,channels, outSampleRate, clientUid, clientPid);
}10.frameworks/av/media/libstagefright/AudioSource.cpp
AudioSource::AudioSource( audio_source_t inputSource, const String16 &opPackageName,uint32_t sampleRate, uint32_t channelCount, uint32_t outSampleRate,uid_t uid, pid_t pid)
{status_t status = AudioRecord::getMinFrameCount(&minFrameCount,sampleRate,AUDIO_FORMAT_PCM_16_BIT,                                         audio_channel_in_mask_from_count(channelCount));mRecord = new AudioRecord(inputSource, sampleRate, AUDIO_FORMAT_PCM_16_BIT,audio_channel_in_mask_from_count(channelCount),opPackageName,(size_t) (bufCount * frameCount),AudioRecordCallbackFunction,this,frameCount /*notificationFrames*/,AUDIO_SESSION_ALLOCATE,AudioRecord::TRANSFER_DEFAULT,AUDIO_INPUT_FLAG_NONE,uid,pid);
}11.frameworks/av/media/libmedia/AudioRecord.cpp
AudioRecord::AudioRecord( audio_source_t inputSource,uint32_t sampleRate,audio_format_t format,audio_channel_mask_t channelMask,const String16& opPackageName,size_t frameCount,callback_t cbf,void* user,uint32_t notificationFrames,audio_session_t sessionId,transfer_type transferType,audio_input_flags_t flags,int uid,pid_t pid,const audio_attributes_t* pAttributes){set(inputSource, sampleRate, format, channelMask, frameCount, cbf, user,notificationFrames, false /*threadCanCallJava*/, sessionId, transferType,
flags, uid, pid, pAttributes);
}今天就到这吧，有时间可以继续往下跟...

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