IjkPlayer 源码阅读一 初始化

详见我的简书 http://www.jianshu.com/p/9b0675da8380

1 背景

公司的底层播放器实际上是ffplayer作为基础修改的，当然需要好好学习研究。 记录下来，作为以后备忘。（发觉人老了，就容易忘事）。ps 入坑需谨慎，很容易入门到放弃。

2 分析入口

分析的连接https://github.com/Bilibili/ijkplayer
版本号： 0.8.1.2 android版
基本上IjkPlayer的接口和MediaPlayer接口一致。http://www.jianshu.com/p/55fbfd5b564a
每次我们发觉分析源码总找不到下口的地方，实际上就是没找到分析的入口。那在哪里呢？当然看源码demo了。https://github.com/Bilibili/ijkplayer/blob/5b73bf7eae66a3942e2689ecbe6e51b679abe161/android/ijkplayer/ijkplayer-example/src/main/java/tv/danmaku/ijk/media/example/activities/VideoActivity.java
这个类里面的onCreate 方法里面：

image.png

实际上初始化，作者已注释了 init player。我们来看看初始化里做了什么？

3 IjkMediaPlayer.loadLibrariesOnce(null);

这个很简单load了几个需要的lib（ijkffmpeg，ijksdl，ijkplayer）

image.png

事实上这里还有隐藏逻辑，看其中源码，你会发现，卧槽，我都找不到定义jni的方法名，熟悉jni的同学知道，jni方法名是Java+ 全类名 命名，可是你会发觉比如你想找到_start方法，你是找不到的。 这里使用的一个trick ， 事实上我觉得这对写代码的人，
提高了写作效率，但可读性没那么高。在jni加载lib的时候，会首先查找JNI_OnLoad() 方法，同理卸载的时候JNI_OnUnload()。我们看下他都干了些啥？
a. 这个是ijkplayer_jni做的

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 },
    { "getCurrentPosition",     "()J",      (void *) IjkMediaPlayer_getCurrentPosition },
    { "getDuration",            "()J",      (void *) IjkMediaPlayer_getDuration },
    { "_release",               "()V",      (void *) IjkMediaPlayer_release },
    { "_reset",                 "()V",      (void *) IjkMediaPlayer_reset },
    { "setVolume",              "(FF)V",    (void *) IjkMediaPlayer_setVolume },
    { "getAudioSessionId",      "()I",      (void *) IjkMediaPlayer_getAudioSessionId },
    { "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 },

    { "_getColorFormatName",    "(I)Ljava/lang/String;",    (void *) IjkMediaPlayer_getColorFormatName },
    { "_getVideoCodecInfo",     "()Ljava/lang/String;",     (void *) IjkMediaPlayer_getVideoCodecInfo },
    { "_getAudioCodecInfo",     "()Ljava/lang/String;",     (void *) IjkMediaPlayer_getAudioCodecInfo },
    { "_getMediaMeta",          "()Landroid/os/Bundle;",    (void *) IjkMediaPlayer_getMediaMeta },
    { "_setLoopCount",          "(I)V",                     (void *) IjkMediaPlayer_setLoopCount },
    { "_getLoopCount",          "()I",                      (void *) IjkMediaPlayer_getLoopCount },
    { "_getPropertyFloat",      "(IF)F",                    (void *) ijkMediaPlayer_getPropertyFloat },
    { "_setPropertyFloat",      "(IF)V",                    (void *) ijkMediaPlayer_setPropertyFloat },
    { "_getPropertyLong",       "(IJ)J",                    (void *) ijkMediaPlayer_getPropertyLong },
    { "_setPropertyLong",       "(IJ)V",                    (void *) ijkMediaPlayer_setPropertyLong },
    { "_setStreamSelected",     "(IZ)V",                    (void *) ijkMediaPlayer_setStreamSelected },

    { "native_profileBegin",    "(Ljava/lang/String;)V",    (void *) IjkMediaPlayer_native_profileBegin },
    { "native_profileEnd",      "()V",                      (void *) IjkMediaPlayer_native_profileEnd },

    { "native_setLogLevel",     "(I)V",                     (void *) IjkMediaPlayer_native_setLogLevel },
    { "_injectCacheNode",       "(IJJJJ)V",                 (void *) IjkMediaPlayer_injectCacheNode },
};

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 LocalReference
    IJK_FIND_JAVA_CLASS(env, g_clazz.clazz, JNI_CLASS_IJKPLAYER);
    (*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;
}

来依次看

#define IJK_FIND_JAVA_CLASS(env__, var__, classsign__) \
    do { \
        jclass clazz = (*env__)->FindClass(env__, classsign__); \
        if (J4A_ExceptionCheck__catchAll(env) || !(clazz)) { \
            ALOGE("FindClass failed: %s", classsign__); \
            return -1; \
        } \
        var__ = (*env__)->NewGlobalRef(env__, clazz); \
        if (J4A_ExceptionCheck__catchAll(env) || !(var__)) { \
            ALOGE("FindClass::NewGlobalRef failed: %s", classsign__); \
            (*env__)->DeleteLocalRef(env__, clazz); \
            return -1; \
        } \
        (*env__)->DeleteLocalRef(env__, clazz); \
    } while(0);

这里宏定义的代码块，在ijkplayer非常常见，忍不住吐槽下， do while(0)貌似没其他作用，仅仅为了装逼？ 去掉的话不好么？整个源码里面非常多的 do while(0) 定义的块。这个函数的作用，就是把java class 传递给c。
(*env)->RegisterNatives(env, g_clazz.clazz, g_methods, NELEM(g_methods) ); 这句就是动态注册各个方法了。当然c语言和c++注册的代码稍微有点区别，c++没有env参数。

ijkmp_global_init();

ijkmedia/ijkplayer/ijkplayer.c

void ijkmp_global_init()
 {
         ffp_global_init();
}

哈哈，作为java程序猿，源码缩进格式也看着别扭。继续看ijkmedia/ijkplayer/ff_ffplay.c

void ffp_global_init()
{
    if (g_ffmpeg_global_inited)
        return;

    /* register all codecs, demux and protocols */
    avcodec_register_all();
#if CONFIG_AVDEVICE
    avdevice_register_all();
#endif
#if CONFIG_AVFILTER
    avfilter_register_all();
#endif
    av_register_all();

    ijkav_register_all();

    avformat_network_init();

    av_lockmgr_register(lockmgr);
    av_log_set_callback(ffp_log_callback_brief);

    av_init_packet(&flush_pkt);
    flush_pkt.data = (uint8_t *)&flush_pkt;

    g_ffmpeg_global_inited = true;
}

看到这里你会说，啊，原来ffmpeg的api 初始化都在这里呀，哇咔咔~~ 当然如果想了解细节可以继续跟源码读下去，不想的话，我继续出发了。

ijkmp_global_set_inject_callback(inject_callback)
ijkmedia/ijkplayer/ijkplayer.c

void ijkmp_global_set_inject_callback(ijk_inject_callback cb)
{
    ffp_global_set_inject_callback(cb);
}

别紧张就是一个回调接口。

FFmpegApi_global_init
ijkmedia/ijkplayer/android/ffmpeg_api_jni.c

int FFmpegApi_global_init(JNIEnv *env)
{
    int ret = 0;

    IJK_FIND_JAVA_CLASS(env, g_clazz.clazz, JNI_CLASS_FFMPEG_API);
    (*env)->RegisterNatives(env, g_clazz.clazz, g_methods, NELEM(g_methods));

    return ret;
}

native_profileBegin

这个跟进源码看里面没什么有效的代码，略。

代码位于 https://github.com/Bilibili/ijkplayer/blob/eb265a564f471e91778158156ab49d46bb00197d/android/ijkplayer/ijkplayer-example/src/main/java/tv/danmaku/ijk/media/example/widget/media/IjkVideoView.java

## setVideoURI(Uri.parse(path));
 public void setVideoPath(String path) {
         setVideoURI(Uri.parse(path));
 }

本质上也是调用setVideoURI.

private void setVideoURI(Uri uri, Map headers) {
        mUri = uri;
        mHeaders = headers;
        mSeekWhenPrepared = 0;
        openVideo();
        requestLayout();
        invalidate();
    }

其他的初始化参数略，主要看openVideo()做啥的。

@TargetApi(Build.VERSION_CODES.M)
    private void openVideo() {
        if (mUri == null || mSurfaceHolder == null) {
            // not ready for playback just yet, will try again later
            return;
        }
        // we shouldn't clear the target state, because somebody might have
        // called start() previously
        release(false);

        AudioManager am = (AudioManager) mAppContext.getSystemService(Context.AUDIO_SERVICE);
        am.requestAudioFocus(null, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN);

        try {
            mMediaPlayer = createPlayer(mSettings.getPlayer());

           ....

            String scheme = mUri.getScheme();
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M &&
                    mSettings.getUsingMediaDataSource() &&
                    (TextUtils.isEmpty(scheme) || scheme.equalsIgnoreCase("file"))) {
                IMediaDataSource dataSource = new FileMediaDataSource(new File(mUri.toString()));
                mMediaPlayer.setDataSource(dataSource);
            }  else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
                mMediaPlayer.setDataSource(mAppContext, mUri, mHeaders);
            } else {
                mMediaPlayer.setDataSource(mUri.toString());
            }
            bindSurfaceHolder(mMediaPlayer, mSurfaceHolder);
            mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
            mMediaPlayer.setScreenOnWhilePlaying(true);
            mPrepareStartTime = System.currentTimeMillis();
            mMediaPlayer.prepareAsync();
            if (mHudViewHolder != null)
                mHudViewHolder.setMediaPlayer(mMediaPlayer);

            // REMOVED: mPendingSubtitleTracks

            // we don't set the target state here either, but preserve the
            // target state that was there before.
            mCurrentState = STATE_PREPARING;
            attachMediaController();
        } catch (IOException ex) {
            ...
        } catch (IllegalArgumentException ex) {
          ...
        } finally {
          ...
        }
    }

可以看到一系列参数的初始化。
createPlayer(mSettings.getPlayer()) 这里根据设置，选取播放器。 兼容了系统，ExoPlayer，及IjkPlayer（默认）。

 public IMediaPlayer createPlayer(int playerType) {
        IMediaPlayer mediaPlayer = null;

        switch (playerType) {
            case Settings.PV_PLAYER__IjkExoMediaPlayer: {
                IjkExoMediaPlayer IjkExoMediaPlayer = new IjkExoMediaPlayer(mAppContext);
                mediaPlayer = IjkExoMediaPlayer;
            }
            break;
            case Settings.PV_PLAYER__AndroidMediaPlayer: {
                AndroidMediaPlayer androidMediaPlayer = new AndroidMediaPlayer();
                mediaPlayer = androidMediaPlayer;
            }
            break;
            case Settings.PV_PLAYER__IjkMediaPlayer:
            default: {
                IjkMediaPlayer ijkMediaPlayer = null;
                if (mUri != null) {
                    ijkMediaPlayer = new IjkMediaPlayer();
                  ....

                ...
            }
            break;
        }

        if (mSettings.getEnableDetachedSurfaceTextureView()) {
            mediaPlayer = new TextureMediaPlayer(mediaPlayer);
        }

        return mediaPlayer;
    }

https://github.com/Bilibili/ijkplayer/blob/master/android/ijkplayer/ijkplayer-java/src/main/java/tv/danmaku/ijk/media/player/IjkMediaPlayer.java

    /**
     * Default constructor. Consider using one of the create() methods for
     * synchronously instantiating a IjkMediaPlayer from a Uri or resource.
     * 

     * When done with the IjkMediaPlayer, you should call {@link #release()}, to
     * free the resources. If not released, too many IjkMediaPlayer instances
     * may result in an exception.
     * 
     */
    public IjkMediaPlayer() {
        this(sLocalLibLoader);
    }

    /**
     * do not loadLibaray
     * @param libLoader
     *              custom library loader, can be null.
     */
    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(this));
    }

loadLibrariesOnce 这里再次load下，确保lib被加载。initNativeOnce只是打印。 初始化了EventHandler，及native_setup()。

static void
IjkMediaPlayer_native_setup(JNIEnv *env, jobject thiz, jobject weak_this)
{
    MPTRACE("%s\n", __func__);
    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);
}

代码的层级每次调用都比较深，由于jni的缘故，很容易就走神了。先看ijkmp_android_create().参数是函数指针，函数 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);

    message_loop_n(env, mp);

LABEL_RETURN:
    ijkmp_dec_ref_p(&mp);

    MPTRACE("message_loop exit");
    return 0;
}

message_loop_n 都是做什么的呢？

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);

    while (1) {
        AVMessage msg;

        int retval = ijkmp_get_msg(mp, &msg, 1);
        if (retval < 0)
            break;

        // block-get should never return 0
        assert(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:
            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:
            MPTRACE("FFP_MSG_PREPARED:\n");
            post_event(env, weak_thiz, MEDIA_PREPARED, 0, 0);
            break;
        case FFP_MSG_COMPLETED:
        ...
}

我们发觉这个其实是消息队列形式，看下post_event函数。直接调用了J4AC_IjkMediaPlayer__postEventFromNative(env, weak_this, what, arg1, arg2, NULL) 函数。

 void J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer__postEventFromNative(JNIEnv *env, jobject weakThiz, jint what, jint arg1, jint arg2, jobject obj)
{
    (*env)->CallStaticVoidMethod(env, class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.id, class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.method_postEventFromNative, weakThiz, what, arg1, arg2, obj);
}

其中，class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.method_postEventFromNative
class_id = class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.id;
name = "postEventFromNative";
sign = "(Ljava/lang/Object;IIILjava/lang/Object;)V"; class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.method_postEventFromNative = J4A_GetStaticMethodID__catchAll(env, class_id, name, sign);

所以class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.method_postEventFromNative 本质是调用postEventFromNative android/ijkplayer/ijkplayer-java/src/main/java/tv/danmaku/ijk/media/player/IjkMediaPlayer.java

   @CalledByNative
    private static void postEventFromNative(Object weakThiz, int what,
            int arg1, int arg2, Object obj) {
        if (weakThiz == null)
            return;

        @SuppressWarnings("rawtypes")
        IjkMediaPlayer mp = (IjkMediaPlayer) ((WeakReference) weakThiz).get();
        if (mp == null) {
            return;
        }

        if (what == MEDIA_INFO && arg1 == MEDIA_INFO_STARTED_AS_NEXT) {
            // this acquires the wakelock if needed, and sets the client side
            // state
            mp.start();
        }
        if (mp.mEventHandler != null) {
            Message m = mp.mEventHandler.obtainMessage(what, arg1, arg2, obj);
            mp.mEventHandler.sendMessage(m);
        }
    }

具体是初始化了IjkMediaPlayer 这个结构体，留个坑，单独写个章节介绍其c层数据结构。
位于https://github.com/Bilibili/ijkplayer/blob/eb265a564f471e91778158156ab49d46bb00197d/ijkmedia/ijkplayer/android/ijkplayer_android.c

IjkMediaPlayer *ijkmp_android_create(int(*msg_loop)(void*))
{
    IjkMediaPlayer *mp = ijkmp_create(msg_loop);
    if (!mp)
        goto fail;

    mp->ffplayer->vout = SDL_VoutAndroid_CreateForAndroidSurface();
    if (!mp->ffplayer->vout)
        goto fail;

    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;
}

ijkmp_create 初始化了FFPlayer结构的参数初始化。初始化msg_queue_init 消息队列。af_mutex， vf_mutex 音视频互斥锁。这里涉及的FFPlayer初始化参数很多。

FFPlayer *ffp_create()
{

   ...
    FFPlayer* ffp = (FFPlayer*) av_mallocz(sizeof(FFPlayer));
    if (!ffp)
        return NULL;

    msg_queue_init(&ffp->msg_queue);
    ffp->af_mutex = SDL_CreateMutex();
    ffp->vf_mutex = SDL_CreateMutex();

    ffp_reset_internal(ffp);
    ffp->av_class = &ffp_context_class;
    ffp->meta = ijkmeta_create();

    av_opt_set_defaults(ffp);

    return ffp;
}

回到mp->ffplayer->vout = SDL_VoutAndroid_CreateForAndroidSurface(); 实际是调用 SDL_VoutAndroid_CreateForANativeWindow();
mp->ffplayer->pipeline = ffpipeline_create_from_android(mp->ffplayer); 初始化了IJKFF_Pipeline 结构体。回到IjkMediaPlayer_native_setup 方法。 jni_set_media_player(env, thiz, mp) 其实是调用java的方法set

 void J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer__mNativeMediaPlayer__set(JNIEnv *env, jobject thiz, jlong value)
{
    (*env)->SetLongField(env, thiz, class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.field_mNativeMediaPlayer, value);
}

与postEvent类似，找到mNativeMediaPlayer变量（android/ijkplayer/ijkplayer-java/src/main/java/tv/danmaku/ijk/media/player/IjkMediaPlayer.java）。

回到openVedio函数内mMediaPlayer.setDataSource()， 到c层的ijkmedia/ijkplayer/android/ijkplayer_jni.c IjkMediaPlayer_setDataSourceAndHeaders函数。

static void
IjkMediaPlayer_setDataSourceAndHeaders(
    JNIEnv *env, jobject thiz, jstring path,
    jobjectArray keys, jobjectArray values)
{
    MPTRACE("%s\n", __func__);
    int retval = 0;
    const char *c_path = NULL;
    IjkMediaPlayer *mp = jni_get_media_player(env, thiz);
    JNI_CHECK_GOTO(path, env, "java/lang/IllegalArgumentException", "mpjni: setDataSource: null path", LABEL_RETURN);
    JNI_CHECK_GOTO(mp, env, "java/lang/IllegalStateException", "mpjni: setDataSource: null mp", LABEL_RETURN);

    c_path = (*env)->GetStringUTFChars(env, path, NULL );
    JNI_CHECK_GOTO(c_path, env, "java/lang/OutOfMemoryError", "mpjni: setDataSource: path.string oom", LABEL_RETURN);

    ALOGV("setDataSource: path %s", c_path);
    retval = ijkmp_set_data_source(mp, c_path);
    (*env)->ReleaseStringUTFChars(env, path, c_path);

    IJK_CHECK_MPRET_GOTO(retval, env, LABEL_RETURN);

LABEL_RETURN:
    ijkmp_dec_ref_p(&mp);

ijkmp_set_data_source(mp, c_path) 函数主要代码ijkmp_change_state_l(mp, MP_STATE_INITIALIZED);

void ijkmp_change_state_l(IjkMediaPlayer *mp, int new_state)
{
    mp->mp_state = new_state;
    ffp_notify_msg1(mp->ffplayer, FFP_MSG_PLAYBACK_STATE_CHANGED);
}

发了个FFP_MSG_PLAYBACK_STATE_CHANGED消息，但是我们看message_loop_n里面是没有回调java的。
先分析到这里，有空的话把时序图和其他的类图的坑填上。ps：纠正下java 函数称 method， c，c++叫函数，写作中没转过来。