ffplay.h

//关键结构体
//存储视频包的队列结构
typedef struct PacketQueue {
AVPacketList *first_pkt, *last_pkt;
int nb_packets; 
int size;
SDL_mutex *mutex;
SDL_cond *cond;
} PacketQueue;

//一个视频渲染单元
typedef struct VideoPicture {
  SDL_Overlay *bmp;
int width, height; /* source height & width */
int allocated;
double pts;
} VideoPicture;

//当前视频文件的相关上下文内容
typedef struct VideoState {

AVFormatContext *pFormatCtx;
int             videoStream, audioStream;

double          audio_clock;
AVStream        *audio_st;
PacketQueue     audioq;
AVFrame         audio_frame;
uint8_t         audio_buf[(MAX_AUDIO_FRAME_SIZE * 3) / 2];
unsigned int    audio_buf_size;
unsigned int    audio_buf_index;
AVPacket        audio_pkt;
uint8_t         *audio_pkt_data;
int             audio_pkt_size;
int             audio_hw_buf_size;  
double          frame_timer;
double          frame_last_pts;
double          frame_last_delay;
double          video_clock; ///<pts of last decoded frame / predicted pts of next decoded frame
AVStream        *video_st;
PacketQueue     videoq;

VideoPicture    pictq[VIDEO_PICTURE_QUEUE_SIZE];
int             pictq_size, pictq_rindex, pictq_windex;
SDL_mutex       *pictq_mutex;
SDL_cond        *pictq_cond;

SDL_Thread      *parse_tid;
SDL_Thread      *video_tid;

char            filename[1024];
int             quit;

AVIOContext     *io_context;
struct SwsContext *sws_ctx;
} VideoState;

//关键函数
//获得当前音频的播放时钟（当前最后一次的播放pts）
double get_audio_clock(VideoState *is)

//音频解码方法
int audio_decode_frame(VideoState *is, double *pts_ptr)

//视频帧播放刷新函数
//计算当前播放的时间位置是否同步
void video_refresh_timer(void *userdata)

//获得当前视频播放的时间位置
double synchronize_video(VideoState *is, AVFrame *src_frame, double pts)

//视频播放线程
int video_thread(void *arg)

//音频播放线程
int audio_thread(void *arg)

//音视频流打开
int stream_component_open(VideoState *is, int stream_index)

// tutorial05.c
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavformat/avio.h>
#include <libswscale/swscale.h>
#include <libavutil/avstring.h>
#include <libavutil/time.h>

#include <SDL.h>
#include <SDL_thread.h>

#ifdef __MINGW32__
#undef main /* Prevents SDL from overriding main() */
#endif

#include <stdio.h>
#include <math.h>

#define SDL_AUDIO_BUFFER_SIZE 1024
#define MAX_AUDIO_FRAME_SIZE 192000

#define MAX_AUDIOQ_SIZE (5 * 16 * 1024)
#define MAX_VIDEOQ_SIZE (5 * 256 * 1024)

#define AV_SYNC_THRESHOLD 0.01
#define AV_NOSYNC_THRESHOLD 10.0

#define FF_ALLOC_EVENT   (SDL_USEREVENT)
#define FF_REFRESH_EVENT (SDL_USEREVENT + 1)
#define FF_QUIT_EVENT (SDL_USEREVENT + 2)

#define VIDEO_PICTURE_QUEUE_SIZE 1

typedef struct PacketQueue {
AVPacketList *first_pkt, *last_pkt;
  int nb_packets;
int size;
SDL_mutex *mutex;
SDL_cond *cond;
} PacketQueue;


  typedef struct VideoPicture {
SDL_Overlay *bmp;
int width, height; /* source height & width */
int allocated;
  double pts;
} VideoPicture;

typedef struct VideoState {

  AVFormatContext *pFormatCtx;
int             videoStream, audioStream;

double          audio_clock;
  AVStream        *audio_st;
  PacketQueue     audioq;
AVFrame         audio_frame;
uint8_t         audio_buf[(MAX_AUDIO_FRAME_SIZE * 3) / 2];
unsigned int    audio_buf_size;
unsigned int    audio_buf_index;
AVPacket        audio_pkt;
uint8_t         *audio_pkt_data;
int             audio_pkt_size;
int             audio_hw_buf_size;  
double          frame_timer;
double          frame_last_pts;
double          frame_last_delay;
double          video_clock; ///<pts of last decoded frame / predicted     pts of next decoded frame
AVStream        *video_st;
PacketQueue     videoq;

VideoPicture    pictq[VIDEO_PICTURE_QUEUE_SIZE];
int             pictq_size, pictq_rindex, pictq_windex;
  SDL_mutex       *pictq_mutex;
SDL_cond        *pictq_cond;

SDL_Thread      *parse_tid;
SDL_Thread      *video_tid;

char            filename[1024];
int             quit;

  AVIOContext     *io_context;
struct SwsContext *sws_ctx;
} VideoState;

SDL_Surface     *screen;

/* Since we only have one decoding thread, the Big Struct
 can be global in case we need it. */
VideoState *global_video_state;

void packet_queue_init(PacketQueue *q) {
memset(q, 0, sizeof(PacketQueue));
q->mutex = SDL_CreateMutex();
  q->cond = SDL_CreateCond();
}
int packet_queue_put(PacketQueue *q, AVPacket *pkt) {

AVPacketList *pkt1;
if(av_dup_packet(pkt) < 0) {
return -1;
}
pkt1 = av_malloc(sizeof(AVPacketList));
if (!pkt1)
return -1;
pkt1->pkt = *pkt;
pkt1->next = NULL;

SDL_LockMutex(q->mutex);

if (!q->last_pkt)
q->first_pkt = pkt1;
else
q->last_pkt->next = pkt1;
  q->last_pkt = pkt1;
q->nb_packets++;
q->size += pkt1->pkt.size;
SDL_CondSignal(q->cond);

SDL_UnlockMutex(q->mutex);
  return 0;
}
  static int packet_queue_get(PacketQueue *q, AVPacket *pkt, int   block)
{
  AVPacketList *pkt1;
int ret;

SDL_LockMutex(q->mutex);

  for(;;) {

  if(global_video_state->quit) {
    ret = -1;
  break;
  }

  pkt1 = q->first_pkt;
if (pkt1) {
  q->first_pkt = pkt1->next;
  if (!q->first_pkt)
      q->last_pkt = NULL;
  q->nb_packets--;
  q->size -= pkt1->pkt.size;
  *pkt = pkt1->pkt;
  av_free(pkt1);
  ret = 1;
  break;
} else if (!block) {
  ret = 0;
  break;
} else {
  SDL_CondWait(q->cond, q->mutex);
}
  }
SDL_UnlockMutex(q->mutex);
  return ret;
}
double get_audio_clock(VideoState *is) {
double pts;
int hw_buf_size, bytes_per_sec, n;

pts = is->audio_clock; /* maintained in the audio thread */
hw_buf_size = is->audio_buf_size - is->audio_buf_index;
bytes_per_sec = 0;
n = is->audio_st->codec->channels * 2;
if(is->audio_st) {
bytes_per_sec = is->audio_st->codec->sample_rate * n;
}
if(bytes_per_sec) {
pts -= (double)hw_buf_size / bytes_per_sec;
}
return pts;
}

int audio_decode_frame(VideoState *is, double *pts_ptr) {
int len1, data_size = 0, n;
AVPacket *pkt = &is->audio_pkt;
double pts;

for(;;) {
while(is->audio_pkt_size > 0) {
  int got_frame;
  len1 = avcodec_decode_audio4(is->audio_st->codec, &is->audio_frame, &got_frame, pkt);
  if(len1 < 0) {
    /* if error, skip frame */
    is->audio_pkt_size = 0;
    break;
  }
  if (got_frame)
  {
    data_size =
    av_samples_get_buffer_size
    (
        NULL, 
        is->audio_st->codec->channels,
        is->audio_frame.nb_samples,
        is->audio_st->codec->sample_fmt,
        1
    );
    memcpy(is->audio_buf, is->audio_frame.data[0], data_size);
  }
  is->audio_pkt_data += len1;
  is->audio_pkt_size -= len1;
  if(data_size <= 0) {
/* No data yet, get more frames */
continue;
  }
  pts = is->audio_clock;
  *pts_ptr = pts;
  n = 2 * is->audio_st->codec->channels;
  is->audio_clock += (double)data_size /
(double)(n * is->audio_st->codec->sample_rate);

  /* We have data, return it and come back for more later */
  return data_size;
}
if(pkt->data)
  av_free_packet(pkt);

if(is->quit) {
  return -1;
}
/* next packet */
if(packet_queue_get(&is->audioq, pkt, 1) < 0) {
  return -1;
}
is->audio_pkt_data = pkt->data;
is->audio_pkt_size = pkt->size;
/* if update, update the audio clock w/pts */
if(pkt->pts != AV_NOPTS_VALUE) {
  is->audio_clock = av_q2d(is->audio_st->time_base)*pkt->pts;
}

}
}

void audio_callback(void *userdata, Uint8 *stream, int len) {

  VideoState *is = (VideoState *)userdata;
  int len1, audio_size;
double pts;

while(len > 0) {
if(is->audio_buf_index >= is->audio_buf_size) {
  /* We have already sent all our data; get more */
  audio_size = audio_decode_frame(is, &pts);
  if(audio_size < 0) {
/* If error, output silence */
is->audio_buf_size = 1024;
memset(is->audio_buf, 0, is->audio_buf_size);
  } else {
is->audio_buf_size = audio_size;
  }
  is->audio_buf_index = 0;
}
len1 = is->audio_buf_size - is->audio_buf_index;
if(len1 > len)
  len1 = len;
memcpy(stream, (uint8_t *)is->audio_buf + is->audio_buf_index, len1);
len -= len1;
stream += len1;
is->audio_buf_index += len1;
}
}

static Uint32 sdl_refresh_timer_cb(Uint32 interval, void *opaque) {
SDL_Event event;
event.type = FF_REFRESH_EVENT;
event.user.data1 = opaque;
SDL_PushEvent(&event);
return 0; /* 0 means stop timer */
}

/* schedule a video refresh in 'delay' ms */
static void schedule_refresh(VideoState *is, int delay) {
SDL_AddTimer(delay, sdl_refresh_timer_cb, is);
}

void video_display(VideoState *is) {

SDL_Rect rect;
VideoPicture *vp;
//AVPicture pict;
float aspect_ratio;
  int w, h, x, y;
//int i;

  vp = &is->pictq[is->pictq_rindex];
  if(vp->bmp) {
//YUV
if(is->video_st->codec->sample_aspect_ratio.num == 0) {
  aspect_ratio = 0;
} else {
  aspect_ratio = av_q2d(is->video_st->codec->sample_aspect_ratio) *
is->video_st->codec->width / is->video_st->codec->height;
}
if(aspect_ratio <= 0.0) {
  aspect_ratio = (float)is->video_st->codec->width /
(float)is->video_st->codec->height;
}
h = screen->h;
w = ((int)rint(h * aspect_ratio)) & -3;
if(w > screen->w) {
  w = screen->w;
  h = ((int)rint(w / aspect_ratio)) & -3;
}
x = (screen->w - w) / 2;
y = (screen->h - h) / 2;

rect.x = x;
rect.y = y;
rect.w = w;
rect.h = h;
SDL_DisplayYUVOverlay(vp->bmp, &rect);
}
}

void video_refresh_timer(void *userdata) {

VideoState *is = (VideoState *)userdata;
VideoPicture *vp;
  double actual_delay, delay, sync_threshold, ref_clock, diff;

if(is->video_st) {
if(is->pictq_size == 0) {
  //当队列中的不存在未处理的图片时，进行延时等待，等待时间为10ms
  schedule_refresh(is, 1);
} else {
  vp = &is->pictq[is->pictq_rindex];

  delay = vp->pts - is->frame_last_pts; /* the pts from last time */
  if(delay <= 0 || delay >= 1.0) {
    /* if incorrect delay, use previous one */
    delay = is->frame_last_delay;
  }
  /* save for next time */
  is->frame_last_delay = delay;
  is->frame_last_pts = vp->pts;

  /* update delay to sync to audio */
  ref_clock = get_audio_clock(is);
  diff = vp->pts - ref_clock;

  /* Skip or repeat the frame. Take delay into account
 FFPlay still doesn't "know if this is the best guess." */
  sync_threshold = (delay > AV_SYNC_THRESHOLD) ? delay : AV_SYNC_THRESHOLD;
  if(fabs(diff) < AV_NOSYNC_THRESHOLD) {
    if(diff <= -sync_threshold) {
      delay = 0;
    } else if(diff >= sync_threshold) {
      delay = 2 * delay;
    }
  }
  is->frame_timer += delay;
  /* computer the REAL delay */
  actual_delay = is->frame_timer - (av_gettime() / 1000000.0);
  if(actual_delay < 0.010) {
/* Really it should skip the picture instead */
actual_delay = 0.010;
  }
  schedule_refresh(is, (int)(actual_delay * 1000 + 0.5));
  /* show the picture! */
  video_display(is);
  
  /* update queue for next picture! */
  if(++is->pictq_rindex == VIDEO_PICTURE_QUEUE_SIZE) {
is->pictq_rindex = 0;
  }
  SDL_LockMutex(is->pictq_mutex);
  is->pictq_size--;
  SDL_CondSignal(is->pictq_cond);
  SDL_UnlockMutex(is->pictq_mutex);
}
  } else {
  schedule_refresh(is, 100);
}
}  
  
void alloc_picture(void *userdata) {

  VideoState *is = (VideoState *)userdata;
VideoPicture *vp;

vp = &is->pictq[is->pictq_windex];
if(vp->bmp) {
  // we already have one make another, bigger/smaller
SDL_FreeYUVOverlay(vp->bmp);
}
// Allocate a place to put our YUV image on that screen
vp->bmp = SDL_CreateYUVOverlay(is->video_st->codec->width,
             is->video_st->codec->height,
             SDL_YV12_OVERLAY,
             screen);
vp->width = is->video_st->codec->width;
vp->height = is->video_st->codec->height;

SDL_LockMutex(is->pictq_mutex);
vp->allocated = 1;
SDL_CondSignal(is->pictq_cond);
SDL_UnlockMutex(is->pictq_mutex);

}

int queue_picture(VideoState *is, AVFrame *pFrame, double pts) {

  VideoPicture *vp;
AVPicture pict;

/* wait until we have space for a new pic */
SDL_LockMutex(is->pictq_mutex);
  while(is->pictq_size >= VIDEO_PICTURE_QUEUE_SIZE &&
  !is->quit) {
  SDL_CondWait(is->pictq_cond, is->pictq_mutex);
}
SDL_UnlockMutex(is->pictq_mutex);

if(is->quit)
  return -1;

// windex is set to 0 initially
vp = &is->pictq[is->pictq_windex];

/* allocate or resize the buffer! */
if(!vp->bmp ||
 vp->width != is->video_st->codec->width ||
 vp->height != is->video_st->codec->height) {
SDL_Event event;

vp->allocated = 0;
/* we have to do it in the main thread */
event.type = FF_ALLOC_EVENT;
event.user.data1 = is;
SDL_PushEvent(&event);

/* wait until we have a picture allocated */
SDL_LockMutex(is->pictq_mutex);
while(!vp->allocated && !is->quit) {
  SDL_CondWait(is->pictq_cond, is->pictq_mutex);
}
SDL_UnlockMutex(is->pictq_mutex);
if(is->quit) {
  return -1;
}
}
/* We have a place to put our picture on the queue */
/* If we are skipping a frame, do we set this to null 
   but still return vp->allocated = 1? */


if(vp->bmp) {

SDL_LockYUVOverlay(vp->bmp);

/* point pict at the queue */

pict.data[0] = vp->bmp->pixels[0];
pict.data[1] = vp->bmp->pixels[2];
pict.data[2] = vp->bmp->pixels[1];

pict.linesize[0] = vp->bmp->pitches[0];
pict.linesize[1] = vp->bmp->pitches[2];
pict.linesize[2] = vp->bmp->pitches[1];

// Convert the image into YUV format that SDL uses
sws_scale
(
    is->sws_ctx,
    (uint8_t const * const *)pFrame->data,
    pFrame->linesize,
    0, 
    is->video_st->codec->height, 
    pict.data, 
    pict.linesize
);

SDL_UnlockYUVOverlay(vp->bmp);
vp->pts = pts;

/* now we inform our display thread that we have a pic ready */
if(++is->pictq_windex == VIDEO_PICTURE_QUEUE_SIZE) {
  is->pictq_windex = 0;
}
SDL_LockMutex(is->pictq_mutex);
is->pictq_size++;
SDL_UnlockMutex(is->pictq_mutex);
}
return 0;
}

double synchronize_video(VideoState *is, AVFrame *src_frame, double pts) {

double frame_delay;

if(pts != 0) {
/* if we have pts, set video clock to it */
is->video_clock = pts;
} else {
/* if we aren't given a pts, set it to the clock */
pts = is->video_clock;
}
/* update the video clock */
frame_delay = av_q2d(is->video_st->codec->time_base);
/* if we are repeating a frame, adjust clock accordingly */
frame_delay += src_frame->repeat_pict * (frame_delay * 0.5);
is->video_clock += frame_delay;
return pts;
}
uint64_t global_video_pkt_pts = AV_NOPTS_VALUE;

/* These are called whenever we allocate a frame
 * buffer. We use this to store the global_pts in
 * a frame at the time it is allocated.
 */
int our_get_buffer(struct AVCodecContext *c, AVFrame *pic) {
  int ret = avcodec_default_get_buffer(c, pic);
uint64_t *pts = av_malloc(sizeof(uint64_t));
*pts = global_video_pkt_pts;
pic->opaque = pts;
return ret;
}
void our_release_buffer(struct AVCodecContext *c, AVFrame *pic)   {
if(pic) av_freep(&pic->opaque);
avcodec_default_release_buffer(c, pic);
}

int video_thread(void *arg) {
VideoState *is = (VideoState *)arg;
AVPacket pkt1, *packet = &pkt1;
int frameFinished;
AVFrame *pFrame;
double pts;

pFrame = av_frame_alloc();

for(;;) {
if(packet_queue_get(&is->videoq, packet, 1) < 0) {
  // means we quit getting packets
  break;
}
pts = 0;

// Save global pts to be stored in pFrame in first call
global_video_pkt_pts = packet->pts;
// Decode video frame
avcodec_decode_video2(is->video_st->codec, pFrame, &frameFinished, 
            packet);
if(packet->dts == AV_NOPTS_VALUE 
   && pFrame->opaque && *(uint64_t*)pFrame->opaque != AV_NOPTS_VALUE) {
  pts = *(uint64_t *)pFrame->opaque;
} else if(packet->dts != AV_NOPTS_VALUE) {
  pts = packet->dts;
} else {
  pts = 0;
}
pts *= av_q2d(is->video_st->time_base);

// Did we get a video frame?
if(frameFinished) {
  pts = synchronize_video(is, pFrame, pts);
  if(queue_picture(is, pFrame, pts) < 0) {
break;
  }
}
av_free_packet(packet);
}
av_free(pFrame);
return 0;
}

int stream_component_open(VideoState *is, int stream_index) {

AVFormatContext *pFormatCtx = is->pFormatCtx;
AVCodecContext *codecCtx = NULL;
AVCodec *codec = NULL;
AVDictionary *optionsDict = NULL;
SDL_AudioSpec wanted_spec, spec;

if(stream_index < 0 || stream_index >= pFormatCtx->nb_streams) {
return -1;
}

// Get a pointer to the codec context for the video stream
codecCtx = pFormatCtx->streams[stream_index]->codec;

if(codecCtx->codec_type == AVMEDIA_TYPE_AUDIO) {
// Set audio settings from codec info
wanted_spec.freq = codecCtx->sample_rate;
wanted_spec.format = AUDIO_S16SYS;
wanted_spec.channels = codecCtx->channels;
wanted_spec.silence = 0;
wanted_spec.samples = SDL_AUDIO_BUFFER_SIZE;
wanted_spec.callback = audio_callback;
wanted_spec.userdata = is;

if(SDL_OpenAudio(&wanted_spec, &spec) < 0) {
  fprintf(stderr, "SDL_OpenAudio: %s\n", SDL_GetError());
  return -1;
}
is->audio_hw_buf_size = spec.size;

}
codec = avcodec_find_decoder(codecCtx->codec_id);

if(!codec || (avcodec_open2(codecCtx, codec, &optionsDict) < 0)) {
fprintf(stderr, "Unsupported codec!\n");
return -1;
}

switch(codecCtx->codec_type) {
case AVMEDIA_TYPE_AUDIO:
is->audioStream = stream_index;
is->audio_st = pFormatCtx->streams[stream_index];
is->audio_buf_size = 0;
is->audio_buf_index = 0;
memset(&is->audio_pkt, 0, sizeof(is->audio_pkt));
packet_queue_init(&is->audioq);
SDL_PauseAudio(0);
break;
case AVMEDIA_TYPE_VIDEO:
is->videoStream = stream_index;
is->video_st = pFormatCtx->streams[stream_index];

is->frame_timer = (double)av_gettime() / 1000000.0;
is->frame_last_delay = 40e-3;

packet_queue_init(&is->videoq);
is->video_tid = SDL_CreateThread(video_thread, is);
is->sws_ctx =
    sws_getContext
    (
        is->video_st->codec->width,
        is->video_st->codec->height,
        is->video_st->codec->pix_fmt,
        is->video_st->codec->width,
        is->video_st->codec->height,
        PIX_FMT_YUV420P, 
        SWS_BILINEAR, 
        NULL, 
        NULL, 
        NULL
    );
codecCtx->get_buffer2 = our_get_buffer;
codecCtx->release_buffer = our_release_buffer;
break;

default:
break;
}

return 0;
}

int decode_interrupt_cb(void *opaque) {
return (global_video_state && global_video_state->quit);
}

int decode_thread(void *arg) {

VideoState *is = (VideoState *)arg;
AVFormatContext *pFormatCtx = NULL;
AVPacket pkt1, *packet = &pkt1;

AVDictionary *io_dict = NULL;
AVIOInterruptCB callback;

int video_index = -1;
int audio_index = -1;
int i;

is->videoStream=-1;
is->audioStream=-1;

global_video_state = is;
// will interrupt blocking functions if we quit!
callback.callback = decode_interrupt_cb;
callback.opaque = is;
if (avio_open2(&is->io_context, is->filename, 0, &callback, &io_dict))
{
fprintf(stderr, "Unable to open I/O for %s\n", is->filename);
return -1;
}

// Open video file
if(avformat_open_input(&pFormatCtx, is->filename, NULL, NULL)!=0)
return -1; // Couldn't open file

is->pFormatCtx = pFormatCtx;

// Retrieve stream information检索流信息
if(avformat_find_stream_info(pFormatCtx, NULL)<0)
return -1; // Couldn't find stream information

// Dump information about file onto standard error将有关文件的信息转储为标准错误
av_dump_format(pFormatCtx, 0, is->filename, 0);

// Find the first video stream

for(i=0; i<pFormatCtx->nb_streams; i++) {
if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO &&
   video_index < 0) {
  video_index=i;
}
if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO &&
   audio_index < 0) {
  audio_index=i;
}
}
if(audio_index >= 0) {
stream_component_open(is, audio_index);
}
if(video_index >= 0) {
stream_component_open(is, video_index);
}   

if(is->videoStream < 0 || is->audioStream < 0) {
fprintf(stderr, "%s: could not open codecs\n", is->filename);
goto fail;
}

// main decode loop

for(;;) {
if(is->quit) {
  break;
}
// seek stuff goes here
if(is->audioq.size > MAX_AUDIOQ_SIZE ||
   is->videoq.size > MAX_VIDEOQ_SIZE) {
  SDL_Delay(10);
  continue;
}
if(av_read_frame(is->pFormatCtx, packet) < 0) {
  if(is->pFormatCtx->pb->error == 0) {
SDL_Delay(100); /* no error; wait for user input */
continue;
  } else {
break;
  }
}
// Is this a packet from the video stream?
if(packet->stream_index == is->videoStream) {
  packet_queue_put(&is->videoq, packet);
} else if(packet->stream_index == is->audioStream) {
  packet_queue_put(&is->audioq, packet);
} else {
  av_free_packet(packet);
}
}
/* all done - wait for it */
while(!is->quit) {
  SDL_Delay(100);
}

 fail:
{
SDL_Event event;
event.type = FF_QUIT_EVENT;
event.user.data1 = is;
SDL_PushEvent(&event);
}
return 0;
}

int main(int argc, char *argv[]) {

SDL_Event       event;

VideoState      *is;

is = av_mallocz(sizeof(VideoState));

if(argc < 2) {
fprintf(stderr, "Usage: test <file>\n");
exit(1);
}
// Register all formats and codecs
av_register_all();

if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
  fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
  exit(1);
}

  // Make a screen to put our video
#ifndef __DARWIN__
    screen = SDL_SetVideoMode(640, 480, 0, 0);
#else
    screen = SDL_SetVideoMode(640, 480, 24, 0);
#endif
if(!screen) {
fprintf(stderr, "SDL: could not set video mode - exiting\n");
exit(1);
}

av_strlcpy(is->filename, argv[1], 1024);

is->pictq_mutex = SDL_CreateMutex();
is->pictq_cond = SDL_CreateCond();

schedule_refresh(is, 40);

is->parse_tid = SDL_CreateThread(decode_thread, is);
if(!is->parse_tid) {
av_free(is);
return -1;
}

for(;;) {

SDL_WaitEvent(&event);
switch(event.type) {
case FF_QUIT_EVENT:
case SDL_QUIT:
  is->quit = 1;
  /*
   * If the video has finished playing, then both the picture and
   * audio queues are waiting for more data.  Make them stop
   * waiting and terminate normally.
   *如果视频已完成播放，则图片和音频队列都在等待更多数据。 使他们停止等待并正常终止。
   */
  SDL_CondSignal(is->audioq.cond);
  SDL_CondSignal(is->videoq.cond);
  SDL_Quit();
  exit(0);
  break;
case FF_ALLOC_EVENT:
  alloc_picture(event.user.data1);
  break;
case FF_REFRESH_EVENT:
  video_refresh_timer(event.user.data1);
  break;
default:
  break;
}
}
return 0;

}