从demo分析ijk源码四：ijk调用ffplay流程分析

以打开一个网络视频的流程为例，我们需要依次调用IJKMediaPlayer的setDisplay/setSurface、setDataSource、prepareAsync，在收到视频加载成功的OnPreparedListener监听中调用start播放视频。其对应的native方法为
_setVideoSurface、_setDataSource、_prepareAsync，在c调用java的postEventFromNative方法中收到what == MEDIA_PREPARED的消息，表示视频加载成功，回调消息到OnPreparedListener中，再调用_start方法播放视频。

接下来依次分析_setVideoSurface、_setDataSource、_prepareAsync、postEventFromNative、_start是如何调用的？

一、_setVideoSurface

_setVideoSurface在ijkplayer_jni.c中对应的实现方法为IjkMediaPlayer_setVideoSurface

{ "_setVideoSurface",       "(Landroid/view/Surface;)V", (void *) IjkMediaPlayer_setVideoSurface },

IjkMediaPlayer_setVideoSurface

static void
IjkMediaPlayer_setVideoSurface(JNIEnv *env, jobject thiz, jobject jsurface)
{
    MPTRACE("%s\n", __func__);
    IjkMediaPlayer *mp = jni_get_media_player(env, thiz);
    JNI_CHECK_GOTO(mp, env, NULL, "mpjni: setVideoSurface: null mp", LABEL_RETURN);

    ijkmp_android_set_surface(env, mp, jsurface);

LABEL_RETURN:
    ijkmp_dec_ref_p(&mp);
    return;
}

IjkMediaPlayer_setVideoSurface调用ijkmp_android_set_surface方法保存surface
ijkplayer_android.c

void ijkmp_android_set_surface(JNIEnv *env, IjkMediaPlayer *mp, jobject android_surface)
{
    if (!mp)
        return;

    MPTRACE("ijkmp_set_android_surface(surface=%p)", (void*)android_surface);
    pthread_mutex_lock(&mp->mutex);
    ijkmp_android_set_surface_l(env, mp, android_surface);
    pthread_mutex_unlock(&mp->mutex);
    MPTRACE("ijkmp_set_android_surface(surface=%p)=void", (void*)android_surface);
}

void ijkmp_android_set_surface_l(JNIEnv *env, IjkMediaPlayer *mp, jobject android_surface)
{
    if (!mp || !mp->ffplayer || !mp->ffplayer->vout)
        return;

    SDL_VoutAndroid_SetAndroidSurface(env, mp->ffplayer->vout, android_surface);
    ffpipeline_set_surface(env, mp->ffplayer->pipeline, android_surface);
}

void SDL_VoutAndroid_SetAndroidSurface(JNIEnv *env, SDL_Vout *vout, jobject android_surface)
{
    ANativeWindow *native_window = NULL;
    if (android_surface) {
        native_window = ANativeWindow_fromSurface(env, android_surface);
        if (!native_window) {
            ALOGE("%s: ANativeWindow_fromSurface: failed\n", __func__);
            // do not return fail here;
        }
    }

    SDL_VoutAndroid_SetNativeWindow(vout, native_window);
    if (native_window)
        ANativeWindow_release(native_window);
}

ANativeWindow代表的是本地窗口，可以看成NDK提供Native版本的Surface。通过ANativeWindow_fromSurface获得ANativeWindow指针，ANativeWindow_release进行释放。类似Java，可以对它进行lock、unlockAndPost以及通过ANativeWindow_Buffer进行图像数据的修改。

二、_setDataSource

_setDataSource的jni实现方法为IjkMediaPlayer_setDataSourceAndHeaders

    {
        "_setDataSource",
        "(Ljava/lang/String;[Ljava/lang/String;[Ljava/lang/String;)V",
        (void *) IjkMediaPlayer_setDataSourceAndHeaders
    }

IjkMediaPlayer_setDataSourceAndHeaders

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);
    ...
    c_path = (*env)->GetStringUTFChars(env, path, NULL );
    ...
    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

int ijkmp_set_data_source(IjkMediaPlayer *mp, const char *url)
{
    assert(mp);
    assert(url);
    MPTRACE("ijkmp_set_data_source(url=\"%s\")\n", url);
    pthread_mutex_lock(&mp->mutex);
    int retval = ijkmp_set_data_source_l(mp, url);
    pthread_mutex_unlock(&mp->mutex);
    MPTRACE("ijkmp_set_data_source(url=\"%s\")=%d\n", url, retval);
    return retval;
}

保存播放地址，重置播放器状态

static int ijkmp_set_data_source_l(IjkMediaPlayer *mp, const char *url)
{
    assert(mp);
    assert(url);

    // MPST_RET_IF_EQ(mp->mp_state, MP_STATE_IDLE);
    MPST_RET_IF_EQ(mp->mp_state, MP_STATE_INITIALIZED);
    MPST_RET_IF_EQ(mp->mp_state, MP_STATE_ASYNC_PREPARING);
    MPST_RET_IF_EQ(mp->mp_state, MP_STATE_PREPARED);
    MPST_RET_IF_EQ(mp->mp_state, MP_STATE_STARTED);
    MPST_RET_IF_EQ(mp->mp_state, MP_STATE_PAUSED);
    MPST_RET_IF_EQ(mp->mp_state, MP_STATE_COMPLETED);
    MPST_RET_IF_EQ(mp->mp_state, MP_STATE_STOPPED);
    MPST_RET_IF_EQ(mp->mp_state, MP_STATE_ERROR);
    MPST_RET_IF_EQ(mp->mp_state, MP_STATE_END);

    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;
}

三、_prepareAsync

_prepareAsync的jni实现为IjkMediaPlayer_prepareAsync

{ "_prepareAsync",          "()V",      (void *) IjkMediaPlayer_prepareAsync },

IjkMediaPlayer_prepareAsync

static void
IjkMediaPlayer_prepareAsync(JNIEnv *env, jobject thiz)
{
    MPTRACE("%s\n", __func__);
    int retval = 0;
    IjkMediaPlayer *mp = jni_get_media_player(env, thiz);
    JNI_CHECK_GOTO(mp, env, "java/lang/IllegalStateException", "mpjni: prepareAsync: null mp", LABEL_RETURN);

    retval = ijkmp_prepare_async(mp);
    IJK_CHECK_MPRET_GOTO(retval, env, LABEL_RETURN);

LABEL_RETURN:
    ijkmp_dec_ref_p(&mp);
}

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;
}

修改播放器状态为PREPARING(MP_STATE_ASYNC_PREPARING)，启动播放器消息队列&mp->ffplayer->msg_queue，创建消息处理线程mp->msg_thread

static int ijkmp_prepare_async_l(IjkMediaPlayer *mp)
{
    ...
    ijkmp_change_state_l(mp, MP_STATE_ASYNC_PREPARING);

    msg_queue_start(&mp->ffplayer->msg_queue);

    // released in msg_loop
    ijkmp_inc_ref(mp);
    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 打印ijk信息，开始加载数据

int ffp_prepare_async_l(FFPlayer *ffp, const char *file_name)
{
    ...
    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) {
        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

    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 创建数据读取线程
is->read_tid = SDL_CreateThreadEx(&is->_read_tid, read_thread, ffp, "ff_read");

static VideoState *stream_open(FFPlayer *ffp, const char *filename, AVInputFormat *iformat)
{
    assert(!ffp->is);
    VideoState *is;

    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 */
    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;
    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;
    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;

    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;
}

static int read_thread(void *arg) {
    ...
    if (is->video_st && is->video_st->codecpar) {
        AVCodecParameters *codecpar = is->video_st->codecpar;
        ffp_notify_msg3(ffp, FFP_MSG_VIDEO_SIZE_CHANGED, codecpar->width, codecpar->height);
        ffp_notify_msg3(ffp, FFP_MSG_SAR_CHANGED, codecpar->sample_aspect_ratio.num, codecpar->sample_aspect_ratio.den);
    }
    ffp->prepared = true;
    ffp_notify_msg1(ffp, FFP_MSG_PREPARED);
    ...
}

创建解码器

static IJKFF_Pipenode *func_init_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)
        node = ffpipenode_init_decoder_from_android_mediacodec(ffp, pipeline, opaque->weak_vout);

    return node;
}

ffp->node_vdec = ffpipeline_init_video_decoder(ffp->pipeline, ffp);

四、postEventFromNative

以上为例，数据读取成功之后，改变播放器状态

 ffp_notify_msg1(ffp, FFP_MSG_PREPARED);

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;
    msg_queue_put(q, &msg);
}

message_loop_n循环处理消息

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;
            ...
          }
}

通过jni回调消息到java

inline static void post_event(JNIEnv *env, jobject weak_this, int what, int arg1, int arg2)
{
    // MPTRACE("post_event(%p, %p, %d, %d, %d)", (void*)env, (void*) weak_this, what, arg1, arg2);
    J4AC_IjkMediaPlayer__postEventFromNative(env, weak_this, what, arg1, arg2, NULL);
    // MPTRACE("post_event()=void");
}

#define J4AC_IjkMediaPlayer__postEventFromNative J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer__postEventFromNative

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);
}

    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);
    if (class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.method_postEventFromNative == NULL)
        goto fail;

这样在IjkMediaPlayer.java的postEventFromNative方法就收到了视频加载成功的消息

五、_start

_start在jni中的实现方法为IjkMediaPlayer_start

{ "_start",                 "()V",      (void *) IjkMediaPlayer_start },

static void
IjkMediaPlayer_start(JNIEnv *env, jobject thiz)
{
    MPTRACE("%s\n", __func__);
    IjkMediaPlayer *mp = jni_get_media_player(env, thiz);
    JNI_CHECK_GOTO(mp, env, "java/lang/IllegalStateException", "mpjni: start: null mp", LABEL_RETURN);

    ijkmp_start(mp);

LABEL_RETURN:
    ijkmp_dec_ref_p(&mp);
}

ijkmp_start_l执行之后，回调start状态

int ijkmp_start(IjkMediaPlayer *mp)
{
    assert(mp);
    MPTRACE("ijkmp_start()\n");
    pthread_mutex_lock(&mp->mutex);
    int retval = ijkmp_start_l(mp);
    pthread_mutex_unlock(&mp->mutex);
    MPTRACE("ijkmp_start()=%d\n", retval);
    return retval;
}

static int ijkmp_start_l(IjkMediaPlayer *mp)
{
    assert(mp);

    MP_RET_IF_FAILED(ikjmp_chkst_start_l(mp->mp_state));

    ffp_remove_msg(mp->ffplayer, FFP_REQ_START);
    ffp_remove_msg(mp->ffplayer, FFP_REQ_PAUSE);
    ffp_notify_msg1(mp->ffplayer, FFP_REQ_START);

    return 0;
}

        case FFP_REQ_START:
            MPTRACE("ijkmp_get_msg: FFP_REQ_START\n");
            continue_wait_next_msg = 1;
            pthread_mutex_lock(&mp->mutex);
            if (0 == ikjmp_chkst_start_l(mp->mp_state)) {
                // FIXME: 8 check seekable
                if (mp->restart) {
                    if (mp->restart_from_beginning) {
                        av_log(mp->ffplayer, AV_LOG_DEBUG, "ijkmp_get_msg: FFP_REQ_START: restart from beginning\n");
                        retval = ffp_start_from_l(mp->ffplayer, 0);
                        if (retval == 0)
                            ijkmp_change_state_l(mp, MP_STATE_STARTED);
                    } else {
                        av_log(mp->ffplayer, AV_LOG_DEBUG, "ijkmp_get_msg: FFP_REQ_START: restart from seek pos\n");
                        retval = ffp_start_l(mp->ffplayer);
                        if (retval == 0)
                            ijkmp_change_state_l(mp, MP_STATE_STARTED);
                    }
                    mp->restart = 0;
                    mp->restart_from_beginning = 0;
                } else {
                    av_log(mp->ffplayer, AV_LOG_DEBUG, "ijkmp_get_msg: FFP_REQ_START: start on fly\n");
                    retval = ffp_start_l(mp->ffplayer);
                    if (retval == 0)
                        ijkmp_change_state_l(mp, MP_STATE_STARTED);
                }
            }
            pthread_mutex_unlock(&mp->mutex);
            break;

切换播放状态到播放

int ffp_start_l(FFPlayer *ffp)
{
    assert(ffp);
    VideoState *is = ffp->is;
    if (!is)
        return EIJK_NULL_IS_PTR;

    toggle_pause(ffp, 0);
    return 0;
}