ijkplayer 源码分析系列（1）——整体结构总结

前言

本系列基于ijkplayer源码进行总结分析，主要分析从java层—JNI层—C层，作为一个播放器的整体流程，整体结构体如下。

主要结构体

在初始化native_setUp的时候，创建了IjkMediaPlayer、FFPlayer、IJKFF_Pipeline，在prepare阶段通过stream_open创建了VideoState，这几个结构体基本贯穿了整个流程，非常重要

IjkMediaPlayer

表示native层的Player，与Java层一对一绑定。作为Java到c的入口封装。

struct IjkMediaPlayer {
    volatile int ref_count;
    pthread_mutex_t mutex;
    FFPlayer *ffplayer;
​
    int (*msg_loop)(void*);
    SDL_Thread *msg_thread;
    SDL_Thread _msg_thread;
​
    int mp_state;
    char *data_source;
    void *weak_thiz;
​
    int restart;
    int restart_from_beginning;
    int seek_req;
};

FFPlayer

具体的播放器，internal player，包含编码、输出等；代码进入到ff_ffplay.c后，就都使用的是FFPlayer。持有VideoState。

typedef struct FFPlayer {
    VideoState *is;
​
    /* extra fields */
    SDL_Aout *aout;
    SDL_Vout *vout;
    struct IJKFF_Pipeline *pipeline;
    struct IJKFF_Pipenode *node_vdec;
​
    MessageQueue msg_queue;
}

VideoState

VideoState，在stream_open中被创建，表示播放过程中的所有状态。

typedef struct VideoState {
    Clock audclk;
    Clock vidclk;
    Clock extclk;
​
    FrameQueue pictq;
    FrameQueue subpq;
    FrameQueue sampq;
​
    Decoder auddec;
    Decoder viddec;
    Decoder subdec;
​
    PacketQueue audioq;
    PacketQueue subtitleq;
    PacketQueue videoq;
​
    int seek_req;
    double frame_timer;
    int abort_request;
    int force_refresh;
    int paused;
​
}

IJKFF_Pipeline

ffpipeline封装了视频解码器和音频解码器/输出，实现通过函数指针。

// ffpipeline_android.c中
typedef struct IJKFF_Pipeline_Opaque {
    FFPlayer      *ffp;
    SDL_mutex     *surface_mutex;
    jobject        jsurface;
    volatile bool  is_surface_need_reconfigure;

    bool         (*mediacodec_select_callback)(void *opaque, ijkmp_mediacodecinfo_context *mcc);
    void          *mediacodec_select_callback_opaque;

    SDL_Vout      *weak_vout;

    float          left_volume;
    float          right_volume;
} IJKFF_Pipeline_Opaque;

// 在ff_ffpipeline.h
typedef struct IJKFF_Pipeline_Opaque IJKFF_Pipeline_Opaque;
typedef struct IJKFF_Pipeline IJKFF_Pipeline;
struct IJKFF_Pipeline {
    SDL_Class             *opaque_class;
    IJKFF_Pipeline_Opaque *opaque;

    void            (*func_destroy)             (IJKFF_Pipeline *pipeline);
    IJKFF_Pipenode *(*func_open_video_decoder)  (IJKFF_Pipeline *pipeline, FFPlayer *ffp);
    SDL_Aout       *(*func_open_audio_output)   (IJKFF_Pipeline *pipeline, FFPlayer *ffp);
    IJKFF_Pipenode *(*func_init_video_decoder)  (IJKFF_Pipeline *pipeline, FFPlayer *ffp);
    int           (*func_config_video_decoder)  (IJKFF_Pipeline *pipeline, FFPlayer *ffp);
};

IJKFF_Pipeline *ffpipeline_alloc(SDL_Class *opaque_class, size_t opaque_size);
void ffpipeline_free(IJKFF_Pipeline *pipeline);
void ffpipeline_free_p(IJKFF_Pipeline **pipeline);

// 打开视频解码器
IJKFF_Pipenode *ffpipeline_open_video_decoder(IJKFF_Pipeline *pipeline, FFPlayer *ffp);
// 打开音频解码器
SDL_Aout       *ffpipeline_open_audio_output(IJKFF_Pipeline *pipeline, FFPlayer *ffp);

// 异步初始化IJKFF_Pipenode
IJKFF_Pipenode* ffpipeline_init_video_decoder(IJKFF_Pipeline *pipeline, FFPlayer *ffp); 

// 异步初始化视频解码器
int ffpipeline_config_video_decoder(IJKFF_Pipeline *pipeline, FFPlayer *ffp);

初始化流程

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);
}
//ijkmp_android_create
IjkMediaPlayer *ijkmp_android_create(int(*msg_loop)(void*))
{
    //初始化 IjkMediaPlayer结构体
    IjkMediaPlayer *mp = ijkmp_create(msg_loop);
    if (!mp)
        goto fail;
    //  创建SDL_Vout
    mp->ffplayer->vout = SDL_VoutAndroid_CreateForAndroidSurface();
    if (!mp->ffplayer->vout)
        goto fail;
    // 创建IJKFF_Pipeline
    mp->ffplayer->pipeline = ffpipeline_create_from_android(mp->ffplayer);
    if (!mp->ffplayer->pipeline)
        goto fail;
    // 互相绑定s
    ffpipeline_set_vout(mp->ffplayer->pipeline, mp->ffplayer->vout);

    return mp;

fail:
    ijkmp_dec_ref_p(&mp);
    return NULL;
}

IjkMediaPlayer_setDataSource

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;
}
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;
}

IjkMediaPlayer_prepareAsync

调用流程 IjkMediaPlayer_prepareAsync->ijkmp_prepare_async_l->ffp_prepare_async_l->stream_open

stream_open

这个方法就是大杂烩了，封装了所有流程中需要的参数

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;
}

• video_refresh_thread，主要负责音视频同步，以及音视频渲染显示流程。
• read_thread ，负责打开流，创建音视频解码线程，读取packet等流程

message_loop

消息循环队列，IjkMediaPlayer创建的时候赋值，prepare中创建线程，启动loop，实现机制类似android消息队列锁机制的Looper那一套。