IjkPlayer初始化过程

None_Ling

发布于 2018-10-24 14:39:35

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发布于 2018-10-24 14:39:35

文章被收录于专栏：Android相关Android相关

背景

最近调研做视频秒开，使用B站开源的ijkplayer作为播放器。ijkplayer基于ffmpeg的播放器。

ijkplayer使用

创建IjkMediaPlayer对象
通过setDataSource设置播放路径
调用prepareAsync让播放器开始工作

JNI_OnLoad

当ijkplayer.so被加载时，会回调到IjkPlayer_jni.c中的JNI_OnLoad中，最主要调用ijkmp_global_init初始化

ijkPlayer播放流程

在IjkMediaPlayer的构造函数中，
- 会调用loadLibrariesOnce加载libijkffmpeg，ijksdl，ijkplayer这三个so
- 调用native_init打印了一行日志
- 初始化当前线程Looper所使用的Handler
  - 如果在有Looper的子线程初始化的话，则会在该子线程进行消息循环
  - 如果没有Looper的子线程，则使用主线程进行消息循环
- 初始化一个Native层的IjkPlayer的引用

 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));
    }

调用__setDataSource将视频URL传入Native层
调用__prepareAsync告知Native层开始加载解码
Ijkplayer_jni.c是IjkMediaPlayer对应的C文件，其中setup完成以下事情：
- 初始化Native的IjkMediaPlayer对象，在ijkmp_create函数中通过ffp_create初始化FFPlayer对象，并且将message_loop赋予该对象

static void IjkMediaPlayer_native_setup(JNIEnv *env, jobject thiz, jobject weak_this)
{
    MPTRACE("%s\n", __func__);
    // 创建Native层的IjkMediaPlayer对象，并且将message_loop对象赋与mp->msg_loop
    IjkMediaPlayer *mp = ijkmp_android_create(message_loop);
    JNI_CHECK_GOTO(mp, env, "java/lang/OutOfMemoryError", "mpjni: native_setup: ijkmp_create() failed", LABEL_RETURN);
    // 通过JNI将上步创建的IjkMediaPlayer对象的指针地址保存到Java层的mNativeMediaPlayer属性中
    // 并且释放旧的IjkMediaPlayer
    jni_set_media_player(env, thiz, mp);
    // 重新生成IjkMediaPlayer的弱引用赋值mp->weak_thiz;
    ijkmp_set_weak_thiz(mp, (*env)->NewGlobalRef(env, weak_this));
    // 设置ffp的inject_opaque为上述弱引用
    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);
}

setDataSource最终会调用到ijkmp_set_data_source_l
- 将原来的mp->data_source指针释放
- 重新将url生成char *赋值给mp->data_source
- 将ijkmediaplayer对象的状态修改成MP_STATE_INITIALIZED

static int ijkmp_set_data_source_l(IjkMediaPlayer *mp, const char *url)
{
    ...
    freep((void**)&mp->data_source);
    mp->data_source = strdup(url);
    if (!mp->data_source)
        return EIJK_OUT_OF_MEMORY;
    ijkmp_change_state_l(mp, MP_STATE_INITIALIZED);
    return 0;
}

prepareAsync最终也会调用到ijkmp_prepare_async_l中
- 将ijkmediaplayer的状态修改为MP_STATE_ASYNC_PREPARING
- 初始化消息队列&mp->ffplayer->msg_queue
- 初始化消息处理线程，线程处理function为ijk_msg_loop
- 调用ffp_prepare_async_l调用ffmpeg中的方法开始prepare

static int ijkmp_prepare_async_l(IjkMediaPlayer *mp)
{
    ...
    ijkmp_change_state_l(mp, MP_STATE_ASYNC_PREPARING);
    // 向&mp->ffplayer->msg_queue中丢入一个FFP_MSG_FLUSH消息
    // 最终目的只是初始化Native的MessageQueue
    msg_queue_start(&mp->ffplayer->msg_queue);

    // released in msg_loop
    ijkmp_inc_ref(mp);
    // 创建处理消息队列的线程，
    // 向Java层IjkMediaPlayer的postEventFromNative回调
    // 该回调会回调到EventHandler中，而队列中只有FFP_MSG_FLUSH这个消息，这只是一个NOP的测试消息
    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;

    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;
}

ffp_prepare_async_l中真正调用ffmpeg开始准备播放
- 判断url协议是否为rtmp或者rtsp，如果是则取消timeout参数
- 如果url长度大于1024，则加入ijklongurl参数
- 调用stream_open打开视频流，使用FFPlayer播放

int ffp_prepare_async_l(FFPlayer *ffp, const char *file_name)
{
    ...
    if (av_stristart(file_name, "rtmp", NULL) ||
        av_stristart(file_name, "rtsp", NULL)) {
        // There is total different meaning for 'timeout' option in rtmp
        av_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_opt_set_dict(ffp, &ffp->player_opts);
    if (!ffp->aout) {
        ffp->aout = ffpipeline_open_audio_output(ffp->pipeline, ffp);
        if (!ffp->aout)
            return -1;
    }

#if CONFIG_AVFILTER
    if (ffp->vfilter0) {
        GROW_ARRAY(ffp->vfilters_list, ffp->nb_vfilters);
        ffp->vfilters_list[ffp->nb_vfilters - 1] = ffp->vfilter0;
    }
#endif
    //  打开视频流
    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;
}

stream_open开始打开视频流，其中VideoState也就代表着视频当前的状态，包括帧，数据，解码器等等
- 初始化帧队列：&is->pictq，&is->subpq，&is->sampq，Queue大小为16
- 初始化数据包队列：&is->videoq，&is->audioq，&is->subtitleq
- 初始化时针：&is->vidclk，&is->audclk，&is->extclk，代表当前视频video，audio的时刻
- 创建视频刷新的线程is->video_refresh_tid
- 创建视频读取线程is->read_tid
- 调用decoder_init初始化视频解码器

static VideoState *stream_open(FFPlayer *ffp, const char *filename, AVInputFormat *iformat)
{
    VideoState *is;  //  视频内容以及状态
    ...
    /* start video display */
    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;

    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;
    }

    init_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;
    ...
    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;
    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;
}

FFMpeg模块分布

encode/decode模块

用于音视频的编码和解码,存放在libavcodec子目录中

muxer/demuxer模块

用于音频和视频的合并与分离（也称混合器模块），存放在libavformat目录中

内存等常用模块

总结

IjkPlayer在Java层初始化主线程/当前线程的EventHandler用于处理从Native层回调的消息
在Native层初始化IjkMediaPlayer对象
- 将message_loop函数指针赋值，以指定Native层的消息
- 通过ffp_create创建FFPlayer对象
- 初始化IjkMediaPlayer中的Mutex，以及ref_count自增
- 创建SDK_Vout用于图形渲染
- 根据平台特性创建各平台的IJKFF_Pipeline，PipeLine中包括了视频解码、音频输出等功能
将NativeMediaPlayer的指针地址赋值给Java层的mNativeMediaPlayer
当调用prepareAsync时，Native层会从Java层获取之前保存的mNativeMediaPlayer指针地址来获取Native层的IjkMediaPlayer
初始化&mp->ffplayer->msg_queue
启动消息线程&mp->_msg_thread以及消息循环函数ijkmp_msg_loop