知识点：
1、视频自适应滤波器

2、func_run_sync

func_run_sync.png

static int video_thread(void *arg)
{
    FFPlayer *ffp = (FFPlayer *)arg;
    int       ret = 0;

    if (ffp->node_vdec) {
        ret = ffpipenode_run_sync(ffp->node_vdec);
    }
    return ret;
}

int ffpipenode_run_sync(IJKFF_Pipenode *node)
{
    return node->func_run_sync(node);
}

if ((ret = decoder_start(&is->viddec, video_thread, ffp, "ff_video_dec")) < 0)
            goto out;

static int decoder_start(Decoder *d, int (*fn)(void *), void *arg, const char *name)
{
    packet_queue_start(d->queue);
    d->decoder_tid = SDL_CreateThreadEx(&d->_decoder_tid, fn, arg, name);
    if (!d->decoder_tid) {
        av_log(NULL, AV_LOG_ERROR, "SDL_CreateThread(): %s\n", SDL_GetError());
        return AVERROR(ENOMEM);
    }
    return 0;
}

#import "ijksdl_thread_ios.h"
#include "ijksdl/ijksdl_thread.h"

static void *SDL_RunThread(void *data)
{
    @autoreleasepool {
        SDL_Thread *thread = data;
        pthread_setname_np(thread->name);
        thread->retval = thread->func(thread->data);
        return NULL;
    }
}

SDL_Thread *SDL_CreateThreadEx(SDL_Thread *thread, int (*fn)(void *), void *data, const char *name)
{
    thread->func = fn;
    thread->data = data;
    strlcpy(thread->name, name, sizeof(thread->name) - 1);
    int retval = pthread_create(&thread->id, NULL, SDL_RunThread, thread);
    if (retval)
        return NULL;

    return thread;
}

3、ffp_video_thread

ffp_video_thread.png

4、线程

1.png

2.png

3.png

static int video_refresh_thread(void *arg)
{
    FFPlayer *ffp = arg;
    VideoState *is = ffp->is;
    double remaining_time = 0.0;
    while (!is->abort_request) {
        if (remaining_time > 0.0)
            av_usleep((int)(int64_t)(remaining_time * 1000000.0));
        remaining_time = REFRESH_RATE;
        if (is->show_mode != SHOW_MODE_NONE && (!is->paused || is->force_refresh))
            video_refresh(ffp, &remaining_time);
    }

    return 0;
}

/* called to display each frame */
static void video_refresh(FFPlayer *opaque, double *remaining_time)
{
    ......
}

/* this thread gets the stream from the disk or the network */
static int read_thread(void *arg)
{
    ......
    /* open the streams */
    if (st_index[AVMEDIA_TYPE_AUDIO] >= 0) {
        stream_component_open(ffp, st_index[AVMEDIA_TYPE_AUDIO]);
    } else {
        ffp->av_sync_type = AV_SYNC_VIDEO_MASTER;
        is->av_sync_type  = ffp->av_sync_type;
    }
    ......
}

static VideoState *stream_open(FFPlayer *ffp, const char *filename, AVInputFormat *iformat)
{
    ......
    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;
    }
    ......
}

/* open a given stream. Return 0 if OK */
static int stream_component_open(FFPlayer *ffp, int stream_index)
{
    ......
    if ((ret = decoder_start(&is->auddec, audio_thread, ffp, "ff_audio_dec")) < 0)
        goto out;
    ......
    if ((ret = decoder_start(&is->viddec, video_thread, ffp, "ff_video_dec")) < 0)
        goto out;
    ......
    if ((ret = decoder_start(&is->subdec, subtitle_thread, ffp, "ff_subtitle_dec")) < 0)
        goto out;
    ......
}

从以上图1、2、3及代码可以看出在线程read_thread中创建了3个子线程audio_thread、video_thread、subtitle_thread。
video_refresh_thread调用video_refresh（/* called to display each frame /）：显示视频帧。
read_thread（/ this thread gets the stream from the disk or the network */）：获取原始视频流（解码）

5、同步

/* prepare a new audio buffer */
static void sdl_audio_callback(void *opaque, Uint8 *stream, int len)
{
......
}

IJKSDLAudioQueueController

static void IJKSDLAudioQueueOuptutCallback(void * inUserData, AudioQueueRef inAQ, AudioQueueBufferRef inBuffer) {
    @autoreleasepool {
        IJKSDLAudioQueueController* aqController = (__bridge IJKSDLAudioQueueController *) inUserData;

        if (!aqController) {
            // do nothing;
        } else if (aqController->_isPaused || aqController->_isStopped) {
            memset(inBuffer->mAudioData, aqController.spec.silence, inBuffer->mAudioDataByteSize);//暂停音频
        } else {
            (*aqController.spec.callback)(aqController.spec.userdata, inBuffer->mAudioData, inBuffer->mAudioDataByteSize);//播放音频
        }

        AudioQueueEnqueueBuffer(inAQ, inBuffer, 0, NULL);
    }
}

sdl_audio_callback.png

static inline av_const int av_clip(int a, int amin, int amax)
{
    if      (a < amin) return amin;
    else if (a > amax) return amax;
    else               return a;
}

static inline av_const uint8_t av_clip_uint8(int a)
{
    if (a&(~0xFF)) return (-a)>>31;
    else           return a;
}

static inline av_const uint16_t av_clip_uint16(int a)
{
    if (a&(~0xFFFF)) return (-a)>>31;
    else             return a;
}

static inline av_const int16_t av_clip_int16(int a)
{
    if ((a+0x8000) & ~0xFFFF) return (a>>31) ^ 0x7FFF;
    else                      return a;
}

static inline av_const int32_t av_clipl_int32(int64_t a)
{
    if ((a+0x80000000u) & ~UINT64_C(0xFFFFFFFF)) return (a>>63) ^ 0x7FFFFFFF;
    else                                         return a;
}

static inline av_const float av_clipf(float a, float amin, float amax)
{
    if      (a < amin) return amin;
    else if (a > amax) return amax;
    else               return a;
}

6、音频

/**
 * Decode one audio frame and return its uncompressed size.
 *
 * The processed audio frame is decoded, converted if required, and
 * stored in is->audio_buf, with size in bytes given by the return
 * value.
 */
static int audio_decode_frame(FFPlayer *ffp)
{
......
}