/**
* Sets the video encoder to be used for recording. If this method is not
* called, the output file will not contain an video track. Call this after
* setOutputFormat() and before prepare().
*
* @param video_encoder the video encoder to use.
* @throws IllegalStateException if it is called before
* setOutputFormat() or after prepare()
* @see android.media.MediaRecorder.VideoEncoder
*/
public native void setVideoEncoder(int video_encoder)
throws IllegalStateException;123456789101112
這是壹個native方法，根據JNI的規則，我們應該去android_media_MediaRecorder.cpp裏看這個方法的實現：
static void
android_media_MediaRecorder_setVideoEncoder(JNIEnv *env, jobject thiz, jint ve)
{
ALOGV("setVideoEncoder(%d)", ve);
if (ve < VIDEO_ENCODER_DEFAULT || ve >= VIDEO_ENCODER_LIST_END) {
jniThrowException(env, "java/lang/IllegalArgumentException", "Invalid video encoder");
return;
}
sp<MediaRecorder> mr = getMediaRecorder(env, thiz);
process_media_recorder_call(env, mr->setVideoEncoder(ve), "java/lang/RuntimeException", "setVideoEncoder failed.");
}1234567891011
關鍵是最後的兩句，sp是Android 裏的壹個指針，就當沒看見~ 所以最後兩句的意思是調用Native層的MediaRecorder的setVideoEncoder方法。
繼續去MediaRecorder.cpp裏看setVideoEncoder方法：
status_t MediaRecorder::setVideoEncoder(int ve)
{
ALOGV("setVideoEncoder(%d)", ve);
if (mMediaRecorder == NULL) {
ALOGE("media recorder is not initialized yet");
return INVALID_OPERATION;
}
if (!mIsVideoSourceSet) {
ALOGE("try to set the video encoder without setting the video source first");
return INVALID_OPERATION;
}
if (mIsVideoEncoderSet) {
ALOGE("video encoder has already been set");
return INVALID_OPERATION;
}
if (!(mCurrentState & MEDIA_RECORDER_DATASOURCE_CONFIGURED)) {
ALOGE("setVideoEncoder called in an invalid state(%d)", mCurrentState);
return INVALID_OPERATION;
}
status_t ret = mMediaRecorder->setVideoEncoder(ve);
if (OK != ret) {
ALOGV("setVideoEncoder failed: %d", ret);
mCurrentState = MEDIA_RECORDER_ERROR;
return ret;
}
mIsVideoEncoderSet = true;
return ret;
}1234567891011121314151617181920212223242526272829
這裏的mMediaReocorder定義在MediaRecorder.h裏：
sp<IMediaRecorder> mMediaRecorder;1
可見其是壹個IMediaRecorder類型的變量，這是壹個接口類型，看壹下其接口定義，在IMediaRecorder.h中：
class IMediaRecorder: public IInterface
{
public:
DECLARE_META_INTERFACE(MediaRecorder);
virtual status_t setCamera(const sp<hardware::ICamera>& camera,
const sp<ICameraRecordingProxy>& proxy) = 0;
virtual status_t setPreviewSurface(const sp<IGraphicBufferProducer>& surface) = 0;
virtual status_t setVideoSource(int vs) = 0;
virtual status_t setAudioSource(int as) = 0;
virtual status_t setOutputFormat(int of) = 0;
virtual status_t setVideoEncoder(int ve) = 0;
virtual status_t setAudioEncoder(int ae) = 0;
virtual status_t setOutputFile(int fd, int64_t offset, int64_t length) = 0;
virtual status_t setVideoSize(int width, int height) = 0;
virtual status_t setVideoFrameRate(int frames_per_second) = 0;
virtual status_t setParameters(const String8& params) = 0;
virtual status_t setListener(const sp<IMediaRecorderClient>& listener) = 0;
virtual status_t setClientName(const String16& clientName) = 0;
virtual status_t prepare() = 0;
virtual status_t getMaxAmplitude(int* max) = 0;
virtual status_t start() = 0;
virtual status_t stop() = 0;
virtual status_t reset() = 0;
virtual status_t pause() = 0;
virtual status_t resume() = 0;
virtual status_t init() = 0;
virtual status_t close() = 0;
virtual status_t release() = 0;
virtual status_t setInputSurface(const sp<IGraphicBufferConsumer>& surface) = 0;
virtual sp<IGraphicBufferProducer> querySurfaceMediaSource() = 0;
};
// ----------------------------------------------------------------------------
class BnMediaRecorder: public BnInterface<IMediaRecorder>
{
public:
virtual status_t onTransact( uint32_t code,
const Parcel& data,
Parcel* reply,
uint32_t flags = 0);
};12345678910111213141516171819202122232425262728293031323334353637383940414243
吶~關鍵的步驟來了，在以前我基本就追到這，就算完蛋了，不知道怎麽繼續往下追了，後來看Binder相關的內容，知道了BnInterface的作用，這是Binder中關鍵的壹環，我們這就不展開講了，只要記得，接下來我們要追的是BnMediaRecorder這個類。
全局搜索壹下“: public BnMediaRecorder”,也就是去找它的實現類，發現在MediaRecorderClient.h當中有如下的定義：
class MediaRecorderClient : public BnMediaRecorder
{
class ServiceDeathNotifier: public IBinder::DeathRecipient
{
public:
ServiceDeathNotifier(
const sp<IBinder>& service,
const sp<IMediaRecorderClient>& listener,
int which);
virtual ~ServiceDeathNotifier();
virtual void binderDied(const wp<IBinder>& who);
private:
int mWhich;
sp<IBinder> mService;
wp<IMediaRecorderClient> mListener;
};
public:
virtual status_t setCamera(const sp<hardware::ICamera>& camera,
const sp<ICameraRecordingProxy>& proxy);
virtual status_t setPreviewSurface(const sp<IGraphicBufferProducer>& surface);
virtual status_t setVideoSource(int vs);
virtual status_t setAudioSource(int as);
virtual status_t setOutputFormat(int of);
virtual status_t setVideoEncoder(int ve);
virtual status_t setAudioEncoder(int ae);
virtual status_t setOutputFile(int fd, int64_t offset,
int64_t length);
virtual status_t setVideoSize(int width, int height);
virtual status_t setVideoFrameRate(int frames_per_second);
virtual status_t setParameters(const String8& params);
virtual status_t setListener(
const sp<IMediaRecorderClient>& listener);
virtual status_t setClientName(const String16& clientName);
virtual status_t prepare();
virtual status_t getMaxAmplitude(int* max);
virtual status_t start();
virtual status_t stop();
virtual status_t reset();
virtual status_t pause();
virtual status_t resume();
virtual status_t init();
virtual status_t close();
virtual status_t release();
virtual status_t dump(int fd, const Vector<String16>& args);
virtual status_t setInputSurface(const sp<IGraphicBufferConsumer>& surface);
virtual sp<IGraphicBufferProducer> querySurfaceMediaSource();
private:
friend class MediaPlayerService; // for accessing private constructor
MediaRecorderClient(
const sp<MediaPlayerService>& service,
pid_t pid,
const String16& opPackageName);
virtual ~MediaRecorderClient();
sp<IBinder::DeathRecipient> mCameraDeathListener;
sp<IBinder::DeathRecipient> mCodecDeathListener;
pid_t mPid;
Mutex mLock;
MediaRecorderBase *mRecorder;
sp<MediaPlayerService> mMediaPlayerService;
};123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566
那麽我們去MediaRecorderClient.cpp裏看看：
status_t MediaRecorderClient::setVideoEncoder(int ve)
{
ALOGV("setVideoEncoder(%d)", ve);
Mutex::Autolock lock(mLock);
if (mRecorder == NULL) {
ALOGE("recorder is not initialized");
return NO_INIT;
}
return mRecorder->setVideoEncoder((video_encoder)ve);
}12345678910
這裏的mRecorder 定義在MediaRecorderClient.h當中：
MediaRecorderBase *mRecorder;1
來，我們繼續搜索“: public MediaRecorderBase”，在StagefrightRecorder.h中找到了，那麽我們去StagefrightRecorder.cpp當中看看~
status_t StagefrightRecorder::setVideoEncoder(video_encoder ve) {
ALOGV("setVideoEncoder: %d", ve);
if (ve < VIDEO_ENCODER_DEFAULT ||
ve >= VIDEO_ENCODER_LIST_END) {
ALOGE("Invalid video encoder: %d", ve);
return BAD_VALUE;
}
mVideoEncoder = ve;
return OK;
}123456789101112
吶，這就算完了~最後我們會發現MediaRecorder中的接口實現基本到最後都會落在這個StagefrightRecorder.cpp當中。