安卓MediaRecorder(2)录制源码分析
- 前言
- JAVA new MediaRecorder() 源码分析
- MediaRecorder 参数设置
- MediaRecorder.prepare 分析
- MediaRecorder.start 分析
- MediaRecorder.stop 分析
- 结语
本文首发地址 https://blog.csdn.net/CSqingchen/article/details/134634628
最新更新地址 https://gitee.com/chenjim/chenjimblog
前言
通过 前文1,我们已经知道如何使用 MediaRecorder。
本文主要分析一下 Framework 中相关流程。
下图是谷歌提供的 MediaRecorder 状态关系图
JAVA new MediaRecorder() 源码分析
public class MediaRecorder implements AudioRouting,AudioRecordingMonitor,
AudioRecordingMonitorClient,MicrophoneDirection {
static {
// 静态代码块,加载链接 liblibmedia_jni.so
System.loadLibrary("media_jni");
native_init();
}
// 已经废弃
public MediaRecorder() {
// 传入 APP Context
this(ActivityThread.currentApplication());
}
public MediaRecorder(@NonNull Context context) {
// 要求 Context 不为空
Objects.requireNonNull(context);
// 创建EventHandler,主要用于JNI层回调时切换到当前App端线程中
Looper looper;
if ((looper = Looper.myLooper()) != null) {
// 如果当前线程有Looper,就使用当前线程的Looper
mEventHandler = new EventHandler(this, looper);
} else if ((looper = Looper.getMainLooper()) != null) {
// 使用主线程的 Looper,Jni回调信息会在主线程执行
mEventHandler = new EventHandler(this, looper);
} else {
mEventHandler = null;
}
// 录制音频的声道数,此处默认 1 (mono即单声道),2 (stereo即双声道立体声),可以通过 setAudioChannels 修改
mChannelCount = 1;
// 创建弱引用,并初始化
try (ScopedParcelState attributionSourceState = context.getAttributionSource().asScopedParcelState()) {
native_setup(new WeakReference<>(this), ActivityThread.currentPackageName(),
attributionSourceState.getParcel());
}
}
android_media_MediaRecorder.cpp native_init()
获取JAVA层 android.media.MediaRecorder 对象
并将 JAVA 对象的属性 mNativeContext、mSurface、postEventFromNative 保存在 fields
详细代码如下
static void
android_media_MediaRecorder_native_init(JNIEnv *env)
{
jclass clazz;
clazz = env->FindClass("android/media/MediaRecorder");
if (clazz == NULL) {
return;
}
fields.context = env->GetFieldID(clazz, "mNativeContext", "J");
if (fields.context == NULL) {
return;
}
fields.surface = env->GetFieldID(clazz, "mSurface", "Landroid/view/Surface;");
if (fields.surface == NULL) {
return;
}
jclass surface = env->FindClass("android/view/Surface");
if (surface == NULL) {
return;
}
fields.post_event = env->GetStaticMethodID(clazz, "postEventFromNative",
"(Ljava/lang/Object;IIILjava/lang/Object;)V");
if (fields.post_event == NULL) {
return;
}
clazz = env->FindClass("java/util/ArrayList");
if (clazz == NULL) {
return;
}
gArrayListFields.add = env->GetMethodID(clazz, "add", "(Ljava/lang/Object;)Z");
gArrayListFields.classId = static_cast<jclass>(env->NewGlobalRef(clazz));
}
MediaRecorder.java postEventFromNative
这个是Jni消息回来的接口,最终会发到 MediaRecorder.EventHandler 的 handleMessage 中
进而可以通过 MediaRecorder.OnInfoListener 、MediaRecorder.OnErrorListener、
AudioRouting.OnRoutingChangedListener 回调到 APP
对应源码如下
private static void postEventFromNative(Object mediarecorder_ref,
int what, int arg1, int arg2, Object obj) {
MediaRecorder mr = (MediaRecorder)((WeakReference)mediarecorder_ref).get();
if (mr == null) {
return;
}
if (mr.mEventHandler != null) {
Message m = mr.mEventHandler.obtainMessage(what, arg1, arg2, obj);
mr.mEventHandler.sendMessage(m);
}
}
// EventHandler 如下
public class MediaRecorder {
...
private class EventHandler extends Handler {
@Override
public void handleMessage(Message msg) {
switch(msg.what) {
case MEDIA_RECORDER_EVENT_ERROR:
case MEDIA_RECORDER_TRACK_EVENT_ERROR:
if (mOnErrorListener != null)
mOnErrorListener.onError(mMediaRecorder, msg.arg1, msg.arg2);
return;
case MEDIA_RECORDER_EVENT_INFO:
case MEDIA_RECORDER_TRACK_EVENT_INFO:
if (mOnInfoListener != null)
mOnInfoListener.onInfo(mMediaRecorder, msg.arg1, msg.arg2);
return;
case MEDIA_RECORDER_AUDIO_ROUTING_CHANGED:
// 耳机使能的消息
return;
}
}
}
android_media_MediaRecorder.cpp native_setup()
static void
android_media_MediaRecorder_native_setup(JNIEnv *env, jobject thiz, jobject weak_this,
jstring packageName, jobject jAttributionSource)
{
// 构建 JNI 对象 MediaRecorder,attributionSource 可以认为是 JNI 中的上下文 Context
sp<MediaRecorder> mr = new MediaRecorder(attributionSource);
...
// 创建 JNI JNIMediaRecorderListener , 其收到的消息最终通过 fields.post_event 回到JAVA
sp<JNIMediaRecorderListener> listener = new JNIMediaRecorderListener(env, thiz, weak_this);
mr->setListener(listener);
...
// 传递客户端包名,以进行权限跟踪
mr->setClientName(clientName);
// 将创建的 mr 保存到 fields.context,也就是 Java 层 MediaRecorder 中的 mNativeContext
setMediaRecorder(env, thiz, mr);
}
MediaRecorder JNI 构造
// frameworks/av/media/libmedia/mediarecorder.cpp
MediaRecorder::MediaRecorder(const AttributionSourceState &attributionSource): mSurfaceMediaSource(NULL)
{
// 通过 binder 获取 MediaPlayerService
const sp<IMediaPlayerService> service(getMediaPlayerService());
if (service != NULL) {
// 通过 MediaPlayerService 创建 MediaRecorderClient
mMediaRecorder = service->createMediaRecorder(attributionSource);
}
...
}
MediaRecorder 类关系如下
class MediaRecorder : public BnMediaRecorderClient, public virtual IMediaDeathNotifier {...}
class BnMediaRecorderClient: public BnInterface<IMediaRecorderClient> {...}
MediaPlayerService 类关系如下
class MediaPlayerService : public BnMediaPlayerService {...}
class BnMediaPlayerService: public BnInterface<IMediaPlayerService> {...}
MediaPlayerService 中 createMediaRecorder 如下
// frameworks/av/media/libmediaplayerservice/MediaPlayerService.cpp
sp<IMediaRecorder> MediaPlayerService::createMediaRecorder(const AttributionSourceState& attributionSource)
{
...
sp<MediaRecorderClient> recorder = new MediaRecorderClient(this, verifiedAttributionSource);
...
return recorder;
}
MediaRecorderClient 构造如下
// frameworks/av/media/libmediaplayerservice/MediaRecorderClient.cpp
MediaRecorderClient::MediaRecorderClient(const sp<MediaPlayerService>& service,
const AttributionSourceState& attributionSource)
{
// 构造StagefrightRecorder,
mRecorder = new StagefrightRecorder(attributionSource);
mMediaPlayerService = service;
}
StagefrightRecorder 类继承关系如下
struct StagefrightRecorder : public MediaRecorderBase {...}
到此 JAVA 层 new MediaRecord()
相关源码已经分析完成
MediaRecorder 参数设置
Java层 setAudioSource 、 setOutputFormat、setInputSurface 等均调用了 Native 接口,下面以 setAudioSource 为例
// frameworks/base/media/java/android/media/MediaRecorder.java
public native void setAudioSource(@Source int audioSource) throws IllegalStateException;
// frameworks/base/media/jni/android_media_MediaRecorder.cpp
static void android_media_MediaRecorder_setAudioSource(JNIEnv *env, jobject thiz, jint as)
{
...
// 读取初始化时保存的mr
sp<MediaRecorder> mr = getMediaRecorder(env, thiz);
if (mr == NULL) {
jniThrowException(env, "java/lang/IllegalStateException", NULL);
return;
}
process_media_recorder_call(env, mr->setAudioSource(as), "java/lang/RuntimeException", "setAudioSource failed.");
}
// frameworks/av/media/libmedia/mediarecorder.cpp
status_t MediaRecorder::setVideoSource(int vs)
{
...
// 上面知道,这里的 mMediaRecorder 是 MediaRecorderClient
status_t ret = mMediaRecorder->setVideoSource(vs);
return ret;
}
// frameworks/av/media/libmediaplayerservice/MediaRecorderClient.cpp
status_t MediaRecorderClient::setVideoSource(int vs)
{
...
// 上面知道,这里的 mRecorder 是 StagefrightRecorder
return mRecorder->setVideoSource((video_source)vs);
}
// frameworks/av/media/libmediaplayerservice/StagefrightRecorder.cpp
status_t StagefrightRecorder::setVideoSource(video_source vs) {
...
// 最终数据保存在 mVideoSource 中
if (vs == VIDEO_SOURCE_DEFAULT) {
mVideoSource = VIDEO_SOURCE_CAMERA;
} else {
mVideoSource = vs;
}
return OK;
}
同理,其它参数设置多数最终都是保存在 StagefrightRecorder 中,录制相关的流程很多也是在其中控制
本文首发地址 https://blog.csdn.net/CSqingchen/article/details/134634628
MediaRecorder.prepare 分析
依据前面的分析,最终 prepare 真正实现如下
// frameworks/av/media/libmediaplayerservice/StagefrightRecorder.cpp
status_t StagefrightRecorder::prepareInternal() {
...
status_t status = OK;
// 依据不同的输出格式,执行不同的 setup
switch (mOutputFormat) {
case OUTPUT_FORMAT_DEFAULT:
case OUTPUT_FORMAT_THREE_GPP:
case OUTPUT_FORMAT_MPEG_4:
case OUTPUT_FORMAT_WEBM:
status = setupMPEG4orWEBMRecording();
break;
case OUTPUT_FORMAT_AMR_NB:
case OUTPUT_FORMAT_AMR_WB:
status = setupAMRRecording();
break;
case OUTPUT_FORMAT_AAC_ADIF:
case OUTPUT_FORMAT_AAC_ADTS:
status = setupAACRecording();
break;
case OUTPUT_FORMAT_RTP_AVP:
status = setupRTPRecording();
break;
case OUTPUT_FORMAT_MPEG2TS:
status = setupMPEG2TSRecording();
break;
case OUTPUT_FORMAT_OGG:
status = setupOggRecording();
break;
default:
ALOGE("Unsupported output file format: %d", mOutputFormat);
status = UNKNOWN_ERROR;
break;
}
return status;
}
这里我们分析一下录制 MP4 的 prepare 流程 setupMPEG4orWEBMRecording
status_t StagefrightRecorder::setupMPEG4orWEBMRecording() {
// 先清理 MediaWriter
mWriter.clear();
mTotalBitRate = 0;
status_t err = OK;
sp<MediaWriter> writer;
sp<MPEG4Writer> mp4writer;
if (mOutputFormat == OUTPUT_FORMAT_WEBM) {
writer = new WebmWriter(mOutputFd);
} else {
// 我们这里分析 MP4 录制,MPEG4Writer 主要是用来写入编码后的音视频内容
writer = mp4writer = new MPEG4Writer(mOutputFd);
}
if (mVideoSource < VIDEO_SOURCE_LIST_END) {
// 如果编码器未配置,设置默认的编码器
setDefaultVideoEncoderIfNecessary();
sp<MediaSource> mediaSource;
// 设置 视频源
err = setupMediaSource(&mediaSource);
if (err != OK) {
return err;
}
sp<MediaCodecSource> encoder;
// 编码参数配置,然后通过 MediaCodecSource::Create 创建编码器
err = setupVideoEncoder(mediaSource, &encoder);
if (err != OK) {
return err;
}
// MPEG4Writer 添加编码通道,一般会有audio、video 两个,这里是 video
writer->addSource(encoder);
mVideoEncoderSource = encoder;
// 输出文件的码率,是视频和音频总码率之和
mTotalBitRate += mVideoBitRate;
}
// Audio source is added at the end if it exists.
// This help make sure that the "recoding" sound is suppressed for
// camcorder applications in the recorded files.
// disable audio for time lapse recording
const bool disableAudio = mCaptureFpsEnable && mCaptureFps < mFrameRate;
if (!disableAudio && mAudioSource != AUDIO_SOURCE_CNT) {
// 通过 createAudioSource() 配置音频编码参数,进而通过 MediaCodecSource::Create 创建 编码器
err = setupAudioEncoder(writer);
if (err != OK) return err;
mTotalBitRate += mAudioBitRate;
}
...
// 监听 MPEG4Writer 一些参数的回调
writer->setListener(mListener);
mWriter = writer;
return OK;
}
通过如上,可以看到 MediaRecorder.prepare 主要是进行参数的配置、编码器的初始化
MediaRecorder.start 分析
依据前面的分析,最终 start 真正实现如下
// frameworks/av/media/libmediaplayerservice/StagefrightRecorder.cpp
status_t StagefrightRecorder::start() {
Mutex::Autolock autolock(mLock);
if (mOutputFd < 0) {
ALOGE("Output file descriptor is invalid");
return INVALID_OPERATION;
}
status_t status = OK;
if (mVideoSource != VIDEO_SOURCE_SURFACE) {
status = prepareInternal();
if (status != OK) {
return status;
}
}
switch (mOutputFormat) {
case OUTPUT_FORMAT_DEFAULT:
case OUTPUT_FORMAT_THREE_GPP:
case OUTPUT_FORMAT_MPEG_4:
case OUTPUT_FORMAT_WEBM:
{
sp<MetaData> meta = new MetaData;
// 设置 meta 信息
setupMPEG4orWEBMMetaData(&meta);
// MPEG4Writer 传入 meta 信息,
// startWriterThread 开启写入线程
// setupAndStartLooper 启动 ALooper, mReflector 用于信息传递
// 通过 writeFtypBox(MetaData *param) 写入
// startTracks(MetaData *params) 启动音、视频Track,参见 MPEG4Writer::Track::start
status = mWriter->start(meta.get());
break;
}
...
}
if (status != OK) {
// start 异常
mWriter.clear();
mWriter = NULL;
}
if ((status == OK) && (!mStarted)) {
mAnalyticsDirty = true;
mStarted = true;
...
// 用于编码耗电统计
addBatteryData(params);
}
return status;
}
MediaRecorder.stop 分析
依据前面的分析,最终 stop 真正实现如下
// frameworks/av/media/libmediaplayerservice/StagefrightRecorder.cpp
status_t StagefrightRecorder::stop() {
Mutex::Autolock autolock(mLock);
status_t err = OK;
if (mCaptureFpsEnable && mCameraSourceTimeLapse != NULL) {
// 延时录制,详细可参见 CameraSourceTimeLapse.cpp
mCameraSourceTimeLapse->startQuickReadReturns();
mCameraSourceTimeLapse = NULL;
}
int64_t stopTimeUs = systemTime() / 1000;
for (const auto &source : { mAudioEncoderSource, mVideoEncoderSource }) {
// 设置停止时间戳
if (source != nullptr && OK != source->setStopTimeUs(stopTimeUs)) {}
}
if (mWriter != NULL) {
// MPEG4Writer 的停止 ,实际调用其 reset(true, true)
// stopWriterThread() 停止写的线程
// Track 停止
// release 关闭文件,停止释放Looper,资源状态重置
err = mWriter->stop();
mLastSeqNo = mWriter->getSequenceNum();
mWriter.clear();
}
// 写入参数相关信息
flushAndResetMetrics(true);
// 重置参数状态
mDurationRecordedUs = 0;
mDurationPausedUs = 0;
mNPauses = 0;
mTotalPausedDurationUs = 0;
mPauseStartTimeUs = 0;
mStartedRecordingUs = 0;
mGraphicBufferProducer.clear();
mPersistentSurface.clear();
mAudioEncoderSource.clear();
mVideoEncoderSource.clear();
......
return err;
}
结语
到这里,已经完成了 MediaRecorder 录制 Framework 源码的分析。
其它部分流程,可以对照参见 StagefrightRecorder.cpp 中源码。希望对你有所帮助。
如果你在使用MediaRecorder的过程中遇到了其他问题,欢迎留言讨论。
如果你觉得本文还不错,可以点赞+收藏。
相关文章
安卓MediaRecorder(1)录制音频的详细使用
安卓MediaRecorder(2)录制源码分析
安卓MediaRecorder(3)音频采集编码写入源码分析
安卓MediaRecorder(4)视频采集编码写入源码分析
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