Ijkplayer 初始化和prepare源码分析

本文ijkplayer的版本是k0.8.8

一、Ijkplayer 初始化流程

1、Java层 – 在IjkVideoView中创建IMediaPlayer播放器接口

    //创建Java层IMediaPlayermMediaPlayer = createPlayer(mSettings.getPlayer());//根据设置的播放类型创建对应的IMediaPlayerpublic IMediaPlayer createPlayer(int playerType) {IMediaPlayer mediaPlayer = null;switch (playerType) {//创建ExoMediaPlayercase Settings.PV_PLAYER__IjkExoMediaPlayer: {IjkExoMediaPlayer IjkExoMediaPlayer = new IjkExoMediaPlayer(mAppContext);mediaPlayer = IjkExoMediaPlayer;}break;//创建AndroidMediaPlayercase Settings.PV_PLAYER__AndroidMediaPlayer: {AndroidMediaPlayer androidMediaPlayer = new AndroidMediaPlayer();mediaPlayer = androidMediaPlayer;}break;//创建IjkMediaPlayercase Settings.PV_PLAYER__IjkMediaPlayer:default: {IjkMediaPlayer ijkMediaPlayer = null;if (mUri != null) {ijkMediaPlayer = new IjkMediaPlayer();...}mediaPlayer = ijkMediaPlayer;}break;}if (mSettings.getEnableDetachedSurfaceTextureView()) {mediaPlayer = new TextureMediaPlayer(mediaPlayer);}return mediaPlayer;}

默认我们会创建ijkplayer为我们提供的IjkMediaPlayer播放器。

2、Java层 – IjkMediaPlayer构造方法

    public IjkMediaPlayer() {this(sLocalLibLoader);}public IjkMediaPlayer(IjkLibLoader libLoader) {initPlayer(libLoader);}private void initPlayer(IjkLibLoader libLoader) {loadLibrariesOnce(libLoader);initNativeOnce();Looper looper;if ((looper = Looper.myLooper()) != null) {mEventHandler = new EventHandler(this, looper);} else if ((looper = Looper.getMainLooper()) != null) {mEventHandler = new EventHandler(this, looper);} else {mEventHandler = null;}/** Native setup requires a weak reference to our object. It's easier to* create it here than in C++.*/native_setup(new WeakReference<IjkMediaPlayer>(this));}private static void initNativeOnce() {synchronized (IjkMediaPlayer.class) {if (!mIsNativeInitialized) {native_init();mIsNativeInitialized = true;}}}private static native void native_init();private native void native_setup(Object IjkMediaPlayer_this);

可以看到Java层创建IjkMediaPlayer播放器时，会调用 native_init和 native_setup方法做初始化操作。

下面我们看看native层这两个方法做了啥

3、JNI层 – ijkplayer_jni.c – 初始化分析

我们每在Java层声明一个Native方法时，都需要在JNI层声明一个与之对应的方法，并通过注册的方式将两个方法关联在一起。

注册的方式一般分为：动态注册 和 静态注册，一般的开源框架和系统源码都是采用动态注册的。

3.1、注册JNI方法

//加载JNI时会执行JNI_OnLoad
JNIEXPORT jint JNI_OnLoad(JavaVM *vm, void *reserved)
{JNIEnv* env = NULL;g_jvm = vm;if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {return -1;}assert(env != NULL);pthread_mutex_init(&g_clazz.mutex, NULL );// FindClass returns LocalReferenceIJK_FIND_JAVA_CLASS(env, g_clazz.clazz, JNI_CLASS_IJKPLAYER);//动态注册(*env)->RegisterNatives(env, g_clazz.clazz, g_methods, NELEM(g_methods) );ijkmp_global_init();ijkmp_global_set_inject_callback(inject_callback);FFmpegApi_global_init(env);return JNI_VERSION_1_4;
}static JNINativeMethod g_methods[] = {{"_setDataSource","(Ljava/lang/String;[Ljava/lang/String;[Ljava/lang/String;)V",(void *) IjkMediaPlayer_setDataSourceAndHeaders},{ "_setDataSourceFd",       "(I)V",     (void *) IjkMediaPlayer_setDataSourceFd },{ "_setDataSource",         "(Ltv/danmaku/ijk/media/player/misc/IMediaDataSource;)V", (void *)IjkMediaPlayer_setDataSourceCallback },{ "_setAndroidIOCallback",  "(Ltv/danmaku/ijk/media/player/misc/IAndroidIO;)V", (void *)IjkMediaPlayer_setAndroidIOCallback },{ "_setVideoSurface",       "(Landroid/view/Surface;)V", (void *) IjkMediaPlayer_setVideoSurface },{ "_prepareAsync",          "()V",      (void *) IjkMediaPlayer_prepareAsync },{ "_start",                 "()V",      (void *) IjkMediaPlayer_start },{ "_stop",                  "()V",      (void *) IjkMediaPlayer_stop },{ "seekTo",                 "(J)V",     (void *) IjkMediaPlayer_seekTo },{ "_pause",                 "()V",      (void *) IjkMediaPlayer_pause },{ "isPlaying",              "()Z",      (void *) IjkMediaPlayer_isPlaying },...{ "native_init",            "()V",      (void *) IjkMediaPlayer_native_init },{ "native_setup",           "(Ljava/lang/Object;)V", (void *) IjkMediaPlayer_native_setup },{ "native_finalize",        "()V",      (void *) IjkMediaPlayer_native_finalize },{ "_setOption",             "(ILjava/lang/String;Ljava/lang/String;)V", (void *) IjkMediaPlayer_setOption },{ "_setOption",             "(ILjava/lang/String;J)V",                  (void *) IjkMediaPlayer_setOptionLong },...
};

注册需要三个参数分别为：

参数一：Java层声明的native方法
参数二：Java层声明的native方法的方法签名。()表示方法，()里面的内容表示参数的签名，例如I表示int类型入参，V表示返回值void。
参数三：jni方法，也就是native方法的实现方法

可以看到native_init方法JNI层实现是IjkMediaPlayer_native_init方法，native_setup方法JNI层实现是IjkMediaPlayer_native_setup。

还有一些其它常用的方法都会在这里注册。

3.2、IjkMediaPlayer_native_init

static void
IjkMediaPlayer_native_init(JNIEnv *env)
{MPTRACE("%s\n", __func__);
}

啥事没干。下面在看看 native_setup 方法做了啥

3.3、IjkMediaPlayer_native_setup

static void
IjkMediaPlayer_native_setup(JNIEnv *env, jobject thiz, jobject weak_this)
{MPTRACE("%s\n", __func__);//创建native层IjkMediaPlayer结构体IjkMediaPlayer *mp = ijkmp_android_create(message_loop);JNI_CHECK_GOTO(mp, env, "java/lang/OutOfMemoryError", "mpjni: native_setup: ijkmp_create() failed", LABEL_RETURN);jni_set_media_player(env, thiz, mp);ijkmp_set_weak_thiz(mp, (*env)->NewGlobalRef(env, weak_this));ijkmp_set_inject_opaque(mp, ijkmp_get_weak_thiz(mp));ijkmp_set_ijkio_inject_opaque(mp, ijkmp_get_weak_thiz(mp));ijkmp_android_set_mediacodec_select_callback(mp, mediacodec_select_callback, ijkmp_get_weak_thiz(mp));LABEL_RETURN:ijkmp_dec_ref_p(&mp);
}//ijkplayer.c -- 创建c层IjkMediaPlayer结构体
IjkMediaPlayer *ijkmp_android_create(int(*msg_loop)(void*))
{//创建播放器，并设置消息处理函数IjkMediaPlayer *mp = ijkmp_create(msg_loop);if (!mp)goto fail;//创建图像渲染对象 SDL_Voutmp->ffplayer->vout = SDL_VoutAndroid_CreateForAndroidSurface();if (!mp->ffplayer->vout)goto fail;//创建视频解码器、音频输出设备mp->ffplayer->pipeline = ffpipeline_create_from_android(mp->ffplayer);if (!mp->ffplayer->pipeline)goto fail;ffpipeline_set_vout(mp->ffplayer->pipeline, mp->ffplayer->vout);return mp;fail:ijkmp_dec_ref_p(&mp);return NULL;
}

可以看到 native_setup 方法的作用有：

创建了native层的 IjkMediaPlayer
IjkMediaPlayer 绑定了JNI层的消息队列 message_loop。
创建图像渲染对象 SDL_Vout
创建视频解码器、音频输出设备

message_loop 是ijkplayer在JNI层维护的一个消息循环机制，负责处理播放器发送的一些状态，最后通过发射机制把这些状态发送到Java层IjkMediaPlayer类的postEventFromNative方法中。和Handler的消息队列作用类似。

    @CalledByNativeprivate static void postEventFromNative(Object weakThiz, int what,int arg1, int arg2, Object obj) {...}

其它作用目前没有关注。

3.4、创建视频解码器和音频输出设备

IJKFF_Pipeline *ffpipeline_create_from_android(FFPlayer *ffp)
{ALOGD("ffpipeline_create_from_android()\n");IJKFF_Pipeline *pipeline = ffpipeline_alloc(&g_pipeline_class, sizeof(IJKFF_Pipeline_Opaque));if (!pipeline)return pipeline;IJKFF_Pipeline_Opaque *opaque = pipeline->opaque;opaque->ffp                   = ffp;opaque->surface_mutex         = SDL_CreateMutex();opaque->left_volume           = 1.0f;opaque->right_volume          = 1.0f;if (!opaque->surface_mutex) {ALOGE("ffpipeline-android:create SDL_CreateMutex failed\n");goto fail;}pipeline->func_destroy              = func_destroy;// 创建视频解码器pipeline->func_open_video_decoder   = func_open_video_decoder;// 创建音频输出设备pipeline->func_open_audio_output    = func_open_audio_output;// 初始化pipeline->func_init_video_decoder   = func_init_video_decoder;pipeline->func_config_video_decoder = func_config_video_decoder;return pipeline;
fail:ffpipeline_free_p(&pipeline);return NULL;
}

1、创建视频解码器

static IJKFF_Pipenode *func_open_video_decoder(IJKFF_Pipeline *pipeline, FFPlayer *ffp)
{IJKFF_Pipeline_Opaque *opaque = pipeline->opaque;IJKFF_Pipenode        *node = NULL;if (ffp->mediacodec_all_videos || ffp->mediacodec_avc || ffp->mediacodec_hevc || ffp->mediacodec_mpeg2)// 硬解码node = ffpipenode_create_video_decoder_from_android_mediacodec(ffp, pipeline, opaque->weak_vout);if (!node) {// 软解吗node = ffpipenode_create_video_decoder_from_ffplay(ffp);}return node;
}

2、创建音频输出设备

static SDL_Aout *func_open_audio_output(IJKFF_Pipeline *pipeline, FFPlayer *ffp)
{SDL_Aout *aout = NULL;if (ffp->opensles) {//OpenSL ES 输出音频aout = SDL_AoutAndroid_CreateForOpenSLES();} else {//AudioTrack 输出音频aout = SDL_AoutAndroid_CreateForAudioTrack();}if (aout)SDL_AoutSetStereoVolume(aout, pipeline->opaque->left_volume, pipeline->opaque->right_volume);return aout;
}

初始化流程主要记录了这些，下面来看一下prepare流程

二、prepare流程

4、prepare流程

4.1、Java层prepareAsync()

创建好播放器IMediaPlayer后，我们就可以调用它的 prepareAsync() 方法，就可以在准备完成的回调方法中播放。

    @Overridepublic void prepareAsync() throws IllegalStateException {_prepareAsync();}public native void _prepareAsync() throws IllegalStateException;

执行native方法 _prepareAsync() ，在上面 3.1中注册JNI方法我们可以知道_prepareAsync()在JNI层实现方法是 IjkMediaPlayer_prepareAsync

4.2、JNI层 IjkMediaPlayer_prepareAsync

static void
IjkMediaPlayer_prepareAsync(JNIEnv *env, jobject thiz)
{MPTRACE("%s\n", __func__);int retval = 0;//获取c层播放器IjkMediaPlayer *mp = jni_get_media_player(env, thiz);JNI_CHECK_GOTO(mp, env, "java/lang/IllegalStateException", "mpjni: prepareAsync: null mp", LABEL_RETURN);//准备工作retval = ijkmp_prepare_async(mp);IJK_CHECK_MPRET_GOTO(retval, env, LABEL_RETURN);LABEL_RETURN:ijkmp_dec_ref_p(&mp);
}

继续执行 ijkmp_prepare_async

4.3、ijkplayer.c – ijkmp_prepare_async()

int ijkmp_prepare_async(IjkMediaPlayer *mp)
{assert(mp);MPTRACE("ijkmp_prepare_async()\n");pthread_mutex_lock(&mp->mutex);int retval = ijkmp_prepare_async_l(mp);pthread_mutex_unlock(&mp->mutex);MPTRACE("ijkmp_prepare_async()=%d\n", retval);return retval;
}static int ijkmp_prepare_async_l(IjkMediaPlayer *mp)
{assert(mp);...ijkmp_change_state_l(mp, MP_STATE_ASYNC_PREPARING);//启动msg_queuemsg_queue_start(&mp->ffplayer->msg_queue);// released in msg_loopijkmp_inc_ref(mp);//创建消息循环的线程mp->msg_thread = SDL_CreateThreadEx(&mp->_msg_thread, ijkmp_msg_loop, mp, "ff_msg_loop");// msg_thread is detached inside msg_loop// TODO: 9 release weak_thiz if pthread_create() failed;//执行prepare工作int retval = ffp_prepare_async_l(mp->ffplayer, mp->data_source);if (retval < 0) {ijkmp_change_state_l(mp, MP_STATE_ERROR);return retval;}return 0;
}
#### 4.4、ff_ffplay.c - ffp_prepare_async_l()
```c
int ffp_prepare_async_l(FFPlayer *ffp, const char *file_name)
{assert(ffp);assert(!ffp->is);assert(file_name);if (av_stristart(file_name, "rtmp", NULL) ||av_stristart(file_name, "rtsp", NULL)) {// There is total different meaning for 'timeout' option in rtmpav_log(ffp, AV_LOG_WARNING, "remove 'timeout' option for rtmp.\n");av_dict_set(&ffp->format_opts, "timeout", NULL, 0);}/* there is a length limit in avformat */if (strlen(file_name) + 1 > 1024) {av_log(ffp, AV_LOG_ERROR, "%s too long url\n", __func__);if (avio_find_protocol_name("ijklongurl:")) {av_dict_set(&ffp->format_opts, "ijklongurl-url", file_name, 0);file_name = "ijklongurl:";}}av_log(NULL, AV_LOG_INFO, "===== versions =====\n");ffp_show_version_str(ffp, "ijkplayer",      ijk_version_info());ffp_show_version_str(ffp, "FFmpeg",         av_version_info());ffp_show_version_int(ffp, "libavutil",      avutil_version());ffp_show_version_int(ffp, "libavcodec",     avcodec_version());ffp_show_version_int(ffp, "libavformat",    avformat_version());ffp_show_version_int(ffp, "libswscale",     swscale_version());ffp_show_version_int(ffp, "libswresample",  swresample_version());av_log(NULL, AV_LOG_INFO, "===== options =====\n");ffp_show_dict(ffp, "player-opts", ffp->player_opts);ffp_show_dict(ffp, "format-opts", ffp->format_opts);ffp_show_dict(ffp, "codec-opts ", ffp->codec_opts);ffp_show_dict(ffp, "sws-opts   ", ffp->sws_dict);ffp_show_dict(ffp, "swr-opts   ", ffp->swr_opts);av_log(NULL, AV_LOG_INFO, "===================\n");av_opt_set_dict(ffp, &ffp->player_opts);if (!ffp->aout) {//在初始化时候已经创建SDL_Aout，这里把创建好的音频播放设备赋值给 ffp->aoutffp->aout = ffpipeline_open_audio_output(ffp->pipeline, ffp);if (!ffp->aout)return -1;}#if CONFIG_AVFILTERif (ffp->vfilter0) {GROW_ARRAY(ffp->vfilters_list, ffp->nb_vfilters);ffp->vfilters_list[ffp->nb_vfilters - 1] = ffp->vfilter0;}
#endif// 读取音视频流VideoState *is = stream_open(ffp, file_name, NULL);if (!is) {av_log(NULL, AV_LOG_WARNING, "ffp_prepare_async_l: stream_open failed OOM");return EIJK_OUT_OF_MEMORY;}ffp->is = is;ffp->input_filename = av_strdup(file_name);return 0;
}

此方法最后会执行stream_open()方法读取网络或者文件中的音视频流，然后发送准备完成的消息给JNI层，JNI层再把准备完成的消息通过反射发送到Java层

4.5、stream_open()

static VideoState *stream_open(FFPlayer *ffp, const char *filename, AVInputFormat *iformat)
{assert(!ffp->is);// 数据初始化VideoState *is;// 分配结构体并初始化is = av_mallocz(sizeof(VideoState));if (!is)return NULL;is->filename = av_strdup(filename);if (!is->filename)goto fail;is->iformat = iformat;is->ytop    = 0;is->xleft   = 0;
#if defined(__ANDROID__)if (ffp->soundtouch_enable) {is->handle = ijk_soundtouch_create();}
#endif/* start video display */// 初始化帧队列if (frame_queue_init(&is->pictq, &is->videoq, ffp->pictq_size, 1) < 0)goto fail;if (frame_queue_init(&is->subpq, &is->subtitleq, SUBPICTURE_QUEUE_SIZE, 0) < 0)goto fail;if (frame_queue_init(&is->sampq, &is->audioq, SAMPLE_QUEUE_SIZE, 1) < 0)goto fail;// 初始化Packet队列if (packet_queue_init(&is->videoq) < 0 ||packet_queue_init(&is->audioq) < 0 ||packet_queue_init(&is->subtitleq) < 0)goto fail;if (!(is->continue_read_thread = SDL_CreateCond())) {av_log(NULL, AV_LOG_FATAL, "SDL_CreateCond(): %s\n", SDL_GetError());goto fail;}if (!(is->video_accurate_seek_cond = SDL_CreateCond())) {av_log(NULL, AV_LOG_FATAL, "SDL_CreateCond(): %s\n", SDL_GetError());ffp->enable_accurate_seek = 0;}if (!(is->audio_accurate_seek_cond = SDL_CreateCond())) {av_log(NULL, AV_LOG_FATAL, "SDL_CreateCond(): %s\n", SDL_GetError());ffp->enable_accurate_seek = 0;}// 初始化时钟// 时钟序列->queue_serial，实际上指向的是is->videoq.serialinit_clock(&is->vidclk, &is->videoq.serial);init_clock(&is->audclk, &is->audioq.serial);init_clock(&is->extclk, &is->extclk.serial);is->audio_clock_serial = -1;// 初始化音量if (ffp->startup_volume < 0)av_log(NULL, AV_LOG_WARNING, "-volume=%d < 0, setting to 0\n", ffp->startup_volume);if (ffp->startup_volume > 100)av_log(NULL, AV_LOG_WARNING, "-volume=%d > 100, setting to 100\n", ffp->startup_volume);ffp->startup_volume = av_clip(ffp->startup_volume, 0, 100);ffp->startup_volume = av_clip(SDL_MIX_MAXVOLUME * ffp->startup_volume / 100, 0, SDL_MIX_MAXVOLUME);is->audio_volume = ffp->startup_volume;is->muted = 0;// 音视频同步类型：默认以音频为基准is->av_sync_type = ffp->av_sync_type;is->play_mutex = SDL_CreateMutex();is->accurate_seek_mutex = SDL_CreateMutex();ffp->is = is;is->pause_req = !ffp->start_on_prepared;// 创建视频渲染线程is->video_refresh_tid = SDL_CreateThreadEx(&is->_video_refresh_tid, video_refresh_thread, ffp, "ff_vout");if (!is->video_refresh_tid) {av_freep(&ffp->is);return NULL;}is->initialized_decoder = 0;// 创建读取音视频流线程is->read_tid = SDL_CreateThreadEx(&is->_read_tid, read_thread, ffp, "ff_read");if (!is->read_tid) {av_log(NULL, AV_LOG_FATAL, "SDL_CreateThread(): %s\n", SDL_GetError());goto fail;}if (ffp->async_init_decoder && !ffp->video_disable && ffp->video_mime_type && strlen(ffp->video_mime_type) > 0&& ffp->mediacodec_default_name && strlen(ffp->mediacodec_default_name) > 0) {if (ffp->mediacodec_all_videos || ffp->mediacodec_avc || ffp->mediacodec_hevc || ffp->mediacodec_mpeg2) {decoder_init(&is->viddec, NULL, &is->videoq, is->continue_read_thread);ffp->node_vdec = ffpipeline_init_video_decoder(ffp->pipeline, ffp);}}is->initialized_decoder = 1;return is;
fail:is->initialized_decoder = 1;is->abort_request = true;if (is->video_refresh_tid)SDL_WaitThread(is->video_refresh_tid, NULL);stream_close(ffp);return NULL;
}

stream_open方法中，目前关注的作用：

初始化VideoState对象，存储音视频播放状态
初始化Packet和Frame队列
初始化时钟
创建并执行 read_thread 读取音视频流线程
创建并执行 video_refresh_thread 用来渲染视频

4.6、read_thread()

/* this thread gets the stream from the disk or the network */
static int read_thread(void *arg)
{FFPlayer *ffp = arg;VideoState *is = ffp->is;//iformat 输入封装格式的上下文:封装了文件格式相关信息的结构体 , 如视频宽高 , 音频采样率等信息 AVFormatContext *ic = NULL;...//初始化AVFormatContextic = avformat_alloc_context();...if (ffp->iformat_name)is->iformat = av_find_input_format(ffp->iformat_name);//打开音视频地址 ( 文件地址 / 网络地址 )err = avformat_open_input(&ic, is->filename, is->iformat, &ffp->format_opts);...//查找音视频流信息//打开音视频文件成功后 , 从该地址中获取对应的音视频流 , 获取的流赋值给了 AVFormatContext* 结构体的 nb_streams 成员//返回值 >= 0 , 代表打开成功 , 否则失败 ;err = avformat_find_stream_info(ic, opts);.../* open the streams */if (st_index[AVMEDIA_TYPE_AUDIO] >= 0) {//打开音频流stream_component_open(ffp, st_index[AVMEDIA_TYPE_AUDIO]);} else {ffp->av_sync_type = AV_SYNC_VIDEO_MASTER;is->av_sync_type  = ffp->av_sync_type;}ret = -1;if (st_index[AVMEDIA_TYPE_VIDEO] >= 0) {//打开视频流ret = stream_component_open(ffp, st_index[AVMEDIA_TYPE_VIDEO]);}...ffp->prepared = true;//发送准备完成的消息ffp_notify_msg1(ffp, FFP_MSG_PREPARED);...
}

调用 ffp_notify_msg1 发送FFP_MSG_PREPARED 将消息添加到消息队列中

inline static void ffp_notify_msg1(FFPlayer *ffp, int what) {msg_queue_put_simple3(&ffp->msg_queue, what, 0, 0);
}inline static void msg_queue_put_simple3(MessageQueue *q, int what, int arg1, int arg2)
{AVMessage msg;msg_init_msg(&msg);msg.what = what;msg.arg1 = arg1;msg.arg2 = arg2;//消息入队列msg_queue_put(q, &msg);
}

5、JNI层 – ijkplayer_jni.c – 消息循环

5.1、message_loop

static int message_loop(void *arg)
{MPTRACE("%s\n", __func__);JNIEnv *env = NULL;if (JNI_OK != SDL_JNI_SetupThreadEnv(&env)) {ALOGE("%s: SetupThreadEnv failed\n", __func__);return -1;}IjkMediaPlayer *mp = (IjkMediaPlayer*) arg;JNI_CHECK_GOTO(mp, env, NULL, "mpjni: native_message_loop: null mp", LABEL_RETURN);//真正循环的方法message_loop_n(env, mp);LABEL_RETURN:ijkmp_dec_ref_p(&mp);MPTRACE("message_loop exit");return 0;
}

继续查看message_loop_n

5.2、message_loop_n

static void message_loop_n(JNIEnv *env, IjkMediaPlayer *mp)
{jobject weak_thiz = (jobject) ijkmp_get_weak_thiz(mp);JNI_CHECK_GOTO(weak_thiz, env, NULL, "mpjni: message_loop_n: null weak_thiz", LABEL_RETURN);//死循环，不停获取消息while (1) {AVMessage msg;//获取消息，阻塞方法//第三个参数int block：是否阻塞。此处传1，表示没有消息时会阻塞int retval = ijkmp_get_msg(mp, &msg, 1);if (retval < 0)break;// block-get should never return 0assert(retval > 0);switch (msg.what) {case FFP_MSG_FLUSH:MPTRACE("FFP_MSG_FLUSH:\n");post_event(env, weak_thiz, MEDIA_NOP, 0, 0);break;case FFP_MSG_ERROR://播放出错消息MPTRACE("FFP_MSG_ERROR: %d\n", msg.arg1);post_event(env, weak_thiz, MEDIA_ERROR, MEDIA_ERROR_IJK_PLAYER, msg.arg1);break;case FFP_MSG_PREPARED://准备完成消息MPTRACE("FFP_MSG_PREPARED:\n");post_event(env, weak_thiz, MEDIA_PREPARED, 0, 0);break;case FFP_MSG_COMPLETED://播放完毕消息MPTRACE("FFP_MSG_COMPLETED:\n");post_event(env, weak_thiz, MEDIA_PLAYBACK_COMPLETE, 0, 0);...    default:ALOGE("unknown FFP_MSG_xxx(%d)\n", msg.what);break;}msg_free_res(&msg);}LABEL_RETURN:;
}

获取消息之后，会调用 post_event 通过反射机制，调用Java层IjkMediaPlayer类的静态方法：postEventFromNative()。

我们再来看一下获取消息的方法ijkmp_get_msg

5.3、ijkplayer.c – ijkmp_get_msg()

/* need to call msg_free_res for freeing the resouce obtained in msg */
int ijkmp_get_msg(IjkMediaPlayer *mp, AVMessage *msg, int block)
{assert(mp);while (1) {int continue_wait_next_msg = 0;//从消息队列中获取消息，block的值传递的是1，表示阻塞int retval = msg_queue_get(&mp->ffplayer->msg_queue, msg, block);if (retval <= 0)return retval;switch (msg->what) {case FFP_MSG_PREPARED:MPTRACE("ijkmp_get_msg: FFP_MSG_PREPARED\n");pthread_mutex_lock(&mp->mutex);if (mp->mp_state == MP_STATE_ASYNC_PREPARING) {ijkmp_change_state_l(mp, MP_STATE_PREPARED);} else {// FIXME: 1: onError() ?av_log(mp->ffplayer, AV_LOG_DEBUG, "FFP_MSG_PREPARED: expecting mp_state==MP_STATE_ASYNC_PREPARING\n");}if (!mp->ffplayer->start_on_prepared) {ijkmp_change_state_l(mp, MP_STATE_PAUSED);}pthread_mutex_unlock(&mp->mutex);break;...if (continue_wait_next_msg) {msg_free_res(msg);continue;}return retval;}return -1;
}

核心方法还是msg_queue_get 从消息队列里面获取消息。下面就是队列获取元素的实现了

5.4、ff_ffmsg_queue.c – msg_queue_get()

/* return < 0 if aborted, 0 if no msg and > 0 if msg.  */
inline static int msg_queue_get(MessageQueue *q, AVMessage *msg, int block)
{AVMessage *msg1;int ret;//锁SDL_LockMutex(q->mutex);//死循环，不停获取队列的值for (;;) {if (q->abort_request) {ret = -1;break;}//获取队列最新的值msg1 = q->first_msg;//如果first_msg不为空if (msg1) {//赋值操作q->first_msg = msg1->next;if (!q->first_msg)q->last_msg = NULL;q->nb_messages--;*msg = *msg1;msg1->obj = NULL;
#ifdef FFP_MERGEav_free(msg1);
#elsemsg1->next = q->recycle_msg;q->recycle_msg = msg1;
#endifret = 1;break;} else if (!block) {//如果first_msg为空，并且不阻塞就跳出循环ret = 0;break;} else {//bolck为1，在这里阻塞SDL_CondWait(q->cond, q->mutex);}}//解锁SDL_UnlockMutex(q->mutex);return ret;
}

这里就是典型的队列取值得操作，如果没有值就阻塞。

以上就是ijkplayer初始化流程和prepare流程。