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android ijkplayer c層分析-初始化

chenjiang3 / 990人閱讀

摘要：管協(xié)議和編解碼，管渲染顯示，管理播放器。然后是，這個最后會走到基本上以的初始化內(nèi)容居多，開頭的應(yīng)該都是。然后是，的網(wǎng)絡(luò)初始化。這下子與基礎(chǔ)協(xié)議對應(yīng)的各項(xiàng)操作算是找到了。終于分析完了，總結(jié)起來就是各種初始化，協(xié)議的解碼器的網(wǎng)絡(luò)的回調(diào)上層的。

本來這個過程我是不大想寫初始化的過程，覺得網(wǎng)上已經(jīng)有不少文章來分析了。但是在前面的整個分析過程中，暴露了自己對一些問題理解還不夠透徹，因此有必要做一次。
首先是java層：

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));
    }

其實(shí)就2個事情，一個是loadLibrariesOnce，一個是initNativeOnce。前者的代碼就不貼了，就是loadLibrary3個so，分別是ijkffmpeg、ijksdl和ijkplayer。ffmpeg管協(xié)議和編解碼，sdl管渲染顯示，ijkplayer管理播放器。每次調(diào)用loadLibrary都會走到每個so的JNI_OnLoad函數(shù)，也就是說這3個so的最開始初始化都在JNI_OnLoad這個函數(shù)內(nèi)處理。回頭我們再看；后者的initNativeOnce里面實(shí)際上走的是native_init。這個對應(yīng)的是jni的函數(shù)IjkMediaPlayer_native_init。在ijkplayer_jni.c中：

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

什么都沒干，對吧。
回來，看看JNI_OnLoad都干了什么：

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;
}

前面都是通用的一些做法，主要是注冊函數(shù)表，用來在java層能夠調(diào)用c層的函數(shù)。然后是ijkmp_global_init，這個最后會走到ffp_global_init：

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;
}

基本上以ffmpeg的初始化內(nèi)容居多，av開頭的應(yīng)該都是。注冊解碼器，然后協(xié)議的注冊。我們看ijkav_register_all：

void ijkav_register_all(void)
{
    static int initialized;

    if (initialized)
        return;
    initialized = 1;

    av_register_all();

    /* protocols */
    av_log(NULL, AV_LOG_INFO, "===== custom modules begin =====
");
#ifdef __ANDROID__
    IJK_REGISTER_PROTOCOL(ijkmediadatasource);
#endif
    IJK_REGISTER_PROTOCOL(async);
    IJK_REGISTER_PROTOCOL(ijklongurl);
    IJK_REGISTER_PROTOCOL(ijktcphook);
    IJK_REGISTER_PROTOCOL(ijkhttphook);
    IJK_REGISTER_PROTOCOL(ijksegment);
    /* demuxers */
    IJK_REGISTER_DEMUXER(ijklivehook);
    av_log(NULL, AV_LOG_INFO, "===== custom modules end =====
");
}

基本上都是為了支持網(wǎng)絡(luò)傳輸?shù)膮f(xié)議注冊。然后是avformat_network_init，ffmpeg的網(wǎng)絡(luò)初始化。最后到達(dá)ff_network_init，里面就是個WSAStartup。
回來看這么多協(xié)議的注冊，先看下這個宏：

#define IJK_REGISTER_PROTOCOL(x)                                        
    {                                                                   
        extern URLProtocol ijkimp_ff_##x##_protocol;                        
        int ijkav_register_##x##_protocol(URLProtocol *protocol, int protocol_size);
        ijkav_register_##x##_protocol(&ijkimp_ff_##x##_protocol, sizeof(URLProtocol));  
    }

URLProtocol結(jié)構(gòu)是個關(guān)鍵。那么這個結(jié)構(gòu)的填充靠什么呢？看宏的調(diào)用，找到extern后面的部分，搜索下，原來在不少文件里都有，例如ijkurlhook.c文件中：

URLProtocol ijkimp_ff_ijktcphook_protocol = {
    .name                = "ijktcphook",
    .url_open2           = ijktcphook_open,
    .url_read            = ijkurlhook_read,
    .url_write           = ijkurlhook_write,
    .url_close           = ijkurlhook_close,
    .priv_data_size      = sizeof(Context),
    .priv_data_class     = &ijktcphook_context_class,
};

這里已經(jīng)規(guī)定了打開和寫入關(guān)閉等的函數(shù)。這下子與基礎(chǔ)協(xié)議對應(yīng)的各項(xiàng)操作算是找到了。我們來看看不一樣的live的處理：

#define IJK_REGISTER_DEMUXER(x)                                         
    {                                                                   
        extern AVInputFormat ijkff_##x##_demuxer;                       
        ijkav_register_input_format(&ijkff_##x##_demuxer);              
    }

然后會定位到ijklivehook.c文件中的

AVInputFormat ijkff_ijklivehook_demuxer = {
    .name           = "ijklivehook",
    .long_name      = "Live Hook Controller",
    .flags          = AVFMT_NOFILE | AVFMT_TS_DISCONT,
    .priv_data_size = sizeof(Context),
    .read_probe     = ijklivehook_probe,
    .read_header2   = ijklivehook_read_header,
    .read_packet    = ijklivehook_read_packet,
    .read_close     = ijklivehook_read_close,
    .priv_class     = &ijklivehook_class,
};

往下看，以ijklivehook_read_header為例，可以看到內(nèi)部有url的判斷，區(qū)分rtmp和rtsp，這下子清楚了吧。
簡單總結(jié)一下，就是通過URLProtocol這個結(jié)構(gòu)來規(guī)范化所有的協(xié)議，名稱和操作函數(shù)都在這里定義。
回到ffp_global_init，下面進(jìn)行到了av_init_packet。這里插一下一個數(shù)據(jù)結(jié)構(gòu)AVPacket。這個是存儲壓縮編碼數(shù)據(jù)相關(guān)信息的結(jié)構(gòu)體。

typedef struct AVPacket {
    /**
     * A reference to the reference-counted buffer where the packet data is
     * stored.
     * May be NULL, then the packet data is not reference-counted.
     */
    AVBufferRef *buf;
    /**
     * Presentation timestamp in AVStream->time_base units; the time at which
     * the decompressed packet will be presented to the user.
     * Can be AV_NOPTS_VALUE if it is not stored in the file.
     * pts MUST be larger or equal to dts as presentation cannot happen before
     * decompression, unless one wants to view hex dumps. Some formats misuse
     * the terms dts and pts/cts to mean something different. Such timestamps
     * must be converted to true pts/dts before they are stored in AVPacket.
     */
    int64_t pts;
    /**
     * Decompression timestamp in AVStream->time_base units; the time at which
     * the packet is decompressed.
     * Can be AV_NOPTS_VALUE if it is not stored in the file.
     */
    int64_t dts;
    uint8_t *data;
    int   size;
    int   stream_index;
    /**
     * A combination of AV_PKT_FLAG values
     */
    int   flags;
    /**
     * Additional packet data that can be provided by the container.
     * Packet can contain several types of side information.
     */
    AVPacketSideData *side_data;
    int side_data_elems;

    /**
     * Duration of this packet in AVStream->time_base units, 0 if unknown.
     * Equals next_pts - this_pts in presentation order.
     */
    int64_t duration;

    int64_t pos;                            ///< byte position in stream, -1 if unknown

#if FF_API_CONVERGENCE_DURATION
    /**
     * @deprecated Same as the duration field, but as int64_t. This was required
     * for Matroska subtitles, whose duration values could overflow when the
     * duration field was still an int.
     */
    attribute_deprecated
    int64_t convergence_duration;
#endif
} AVPacket;

看到了什么嗎？pts,dts,data。顯示時間戳，解碼時間戳，數(shù)據(jù)。av_init_packet就是個簡單填充，不貼代碼了。回到JNI_OnLoad，然后進(jìn)行的是ijkmp_global_set_inject_callback。
設(shè)置了一個回調(diào)，那么看看具體回調(diào)的約定吧：

static int
inject_callback(void *opaque, int what, void *data, size_t data_size)
{
    JNIEnv     *env     = NULL;
    jobject     jbundle = NULL;
    int         ret     = -1;
    SDL_JNI_SetupThreadEnv(&env);

    jobject weak_thiz = (jobject) opaque;
    if (weak_thiz == NULL )
        goto fail;
    switch (what) {
        case AVAPP_CTRL_WILL_HTTP_OPEN:
        case AVAPP_CTRL_WILL_LIVE_OPEN:
        case AVAPP_CTRL_WILL_CONCAT_SEGMENT_OPEN: {
            AVAppIOControl *real_data = (AVAppIOControl *)data;
            real_data->is_handled = 0;

            jbundle = J4AC_Bundle__Bundle__catchAll(env);
            if (!jbundle) {
                ALOGE("%s: J4AC_Bundle__Bundle__catchAll failed for case %d
", __func__, what);
                goto fail;
            }
            J4AC_Bundle__putString__withCString__catchAll(env, jbundle, "url", real_data->url);
            J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "segment_index", real_data->segment_index);
            J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "retry_counter", real_data->retry_counter);
            real_data->is_handled = J4AC_IjkMediaPlayer__onNativeInvoke(env, weak_thiz, what, jbundle);
            if (J4A_ExceptionCheck__catchAll(env)) {
                goto fail;
            }

            J4AC_Bundle__getString__withCString__asCBuffer(env, jbundle, "url", real_data->url, sizeof(real_data->url));
            if (J4A_ExceptionCheck__catchAll(env)) {
                goto fail;
            }
            ret = 0;
            break;
        }
        case AVAPP_EVENT_WILL_HTTP_OPEN:
        case AVAPP_EVENT_DID_HTTP_OPEN:
        case AVAPP_EVENT_WILL_HTTP_SEEK:
        case AVAPP_EVENT_DID_HTTP_SEEK: {
            AVAppHttpEvent *real_data = (AVAppHttpEvent *) data;
            jbundle = J4AC_Bundle__Bundle__catchAll(env);
            if (!jbundle) {
                ALOGE("%s: J4AC_Bundle__Bundle__catchAll failed for case %d
", __func__, what);
                goto fail;
            }
            J4AC_Bundle__putString__withCString__catchAll(env, jbundle, "url", real_data->url);
            J4AC_Bundle__putLong__withCString__catchAll(env, jbundle, "offset", real_data->offset);
            J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "error", real_data->error);
            J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "http_code", real_data->http_code);
            J4AC_IjkMediaPlayer__onNativeInvoke(env, weak_thiz, what, jbundle);
            if (J4A_ExceptionCheck__catchAll(env))
                goto fail;
            ret = 0;
            break;
        }
        case AVAPP_CTRL_DID_TCP_OPEN:
        case AVAPP_CTRL_WILL_TCP_OPEN: {
            AVAppTcpIOControl *real_data = (AVAppTcpIOControl *)data;
            jbundle = J4AC_Bundle__Bundle__catchAll(env);
            if (!jbundle) {
                ALOGE("%s: J4AC_Bundle__Bundle__catchAll failed for case %d
", __func__, what);
                goto fail;
            }
            J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "error", real_data->error);
            J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "family", real_data->family);
            J4AC_Bundle__putString__withCString__catchAll(env, jbundle, "ip", real_data->ip);
            J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "port", real_data->port);
            J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "fd", real_data->fd);
            J4AC_IjkMediaPlayer__onNativeInvoke(env, weak_thiz, what, jbundle);
            if (J4A_ExceptionCheck__catchAll(env))
                goto fail;
            ret = 0;
            break;
        }
        default: {
            ret = 0;
        }
    }
fail:
    SDL_JNI_DeleteLocalRefP(env, &jbundle);
    return ret;
}

簡單找個函數(shù)看下：J4AC_IjkMediaPlayer__onNativeInvoke，在java層里找到了定義：

private OnNativeInvokeListener mOnNativeInvokeListener;
    public void setOnNativeInvokeListener(OnNativeInvokeListener listener) {
        mOnNativeInvokeListener = listener;
    }

    public interface OnNativeInvokeListener {

        int CTRL_WILL_TCP_OPEN = 0x20001;               // NO ARGS
        int CTRL_DID_TCP_OPEN = 0x20002;                // ARG_ERROR, ARG_FAMILIY, ARG_IP, ARG_PORT, ARG_FD

        int CTRL_WILL_HTTP_OPEN = 0x20003;              // ARG_URL, ARG_SEGMENT_INDEX, ARG_RETRY_COUNTER
        int CTRL_WILL_LIVE_OPEN = 0x20005;              // ARG_URL, ARG_RETRY_COUNTER
        int CTRL_WILL_CONCAT_RESOLVE_SEGMENT = 0x20007; // ARG_URL, ARG_SEGMENT_INDEX, ARG_RETRY_COUNTER

        int EVENT_WILL_HTTP_OPEN = 0x1;                 // ARG_URL
        int EVENT_DID_HTTP_OPEN = 0x2;                  // ARG_URL, ARG_ERROR, ARG_HTTP_CODE
        int EVENT_WILL_HTTP_SEEK = 0x3;                 // ARG_URL, ARG_OFFSET
        int EVENT_DID_HTTP_SEEK = 0x4;                  // ARG_URL, ARG_OFFSET, ARG_ERROR, ARG_HTTP_CODE

        String ARG_URL = "url";
        String ARG_SEGMENT_INDEX = "segment_index";
        String ARG_RETRY_COUNTER = "retry_counter";

        String ARG_ERROR = "error";
        String ARG_FAMILIY = "family";
        String ARG_IP = "ip";
        String ARG_PORT = "port";
        String ARG_FD = "fd";

        String ARG_OFFSET = "offset";
        String ARG_HTTP_CODE = "http_code";

        /*
         * @return true if invoke is handled
         * @throws Exception on any error
         */
        boolean onNativeInvoke(int what, Bundle args);
    }

    @CalledByNative
    private static boolean onNativeInvoke(Object weakThiz, int what, Bundle args) {
        DebugLog.ifmt(TAG, "onNativeInvoke %d", what);
        if (weakThiz == null || !(weakThiz instanceof WeakReference))
            throw new IllegalStateException(".onNativeInvoke()");

        @SuppressWarnings("unchecked")
        WeakReference weakPlayer = (WeakReference) weakThiz;
        IjkMediaPlayer player = weakPlayer.get();
        if (player == null)
            throw new IllegalStateException(".onNativeInvoke()");

        OnNativeInvokeListener listener = player.mOnNativeInvokeListener;
        if (listener != null && listener.onNativeInvoke(what, args))
            return true;

        switch (what) {
            case OnNativeInvokeListener.CTRL_WILL_CONCAT_RESOLVE_SEGMENT: {
                OnControlMessageListener onControlMessageListener = player.mOnControlMessageListener;
                if (onControlMessageListener == null)
                    return false;

                int segmentIndex = args.getInt(OnNativeInvokeListener.ARG_SEGMENT_INDEX, -1);
                if (segmentIndex < 0)
                    throw new InvalidParameterException("onNativeInvoke(invalid segment index)");

                String newUrl = onControlMessageListener.onControlResolveSegmentUrl(segmentIndex);
                if (newUrl == null)
                    throw new RuntimeException(new IOException("onNativeInvoke() = "));

                args.putString(OnNativeInvokeListener.ARG_URL, newUrl);
                return true;
            }
            default:
                return false;
        }
    }

那么可以確定，這里是注冊的回調(diào)，以便通知java層。好吧，回來繼續(xù)JNI_OnLoad，就差FFmpegApi_global_init了：

#define JNI_CLASS_FFMPEG_API "tv/danmaku/ijk/media/player/ffmpeg/FFmpegApi"
......
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;
}

按照定義，找到這個類，只有一句話：

public class FFmpegApi {
    public static native String av_base64_encode(byte in[]);
}

其實(shí)就是個base64的解碼，指向ffmpeg的c函數(shù)，這里進(jìn)行了注冊。
終于分析完了，總結(jié)起來就是各種初始化，協(xié)議的、解碼器的、網(wǎng)絡(luò)的、回調(diào)上層的。

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