目录

这次的代码主要解决了如下问题

存在的问题

 与之前版本的差异点

关于time_base的知识

video显示线程内等待audio的代码

audio线程计算 audio_clock的代码

完整的代码

在上一篇文章中FFMPEG学习（三）ffmpeg+SDL2.0制作简单的视频播放器（图像+声音），我们的代码里播放了MP4文件的音频跟视屏，但是会有音频晚于视屏的问题。这里我们进进行修改，使得视屏的播放基于音频播放时间进行同步

这次的代码主要解决了如下问题

1、播放完成无法自动结束的问题

2、音频与视屏播放无法同步时间问题

存在的问题

1、概率性执行完成之后发生段错，gdb调试暂时没有结论。后续再优化

2、只考虑了音频比视频慢的情况处理，如果银屏比视频更快这个情况，是不是也要在audio线程内等待？

3、代码内视屏播放时间使用的是pts时间，而非dts。这样是否可以考虑到B帧 的dts、pts不相等的问题？

代码逻辑大致如下（暂时未考虑存在B帧的情况，认为视屏的dts与pts相同的前提下）

 与之前版本的差异点

1、主线程是等待video播放线程结束再退出的，解决了播放完成无法退出，必须kill -9强杀的问题

2、一共三条线程

2.1、主线程读取视屏流，放到对应的队列中

2.2、一条音频播放线程，更新播放器的时钟

2.3、一条视屏播放线程，判断播放器时钟与当前帧的pts比较，显示图像

关于time_base的知识

暂时可以理解为ffmpeg内的一种时间单位，等同于提倡生活中的其他单位一样：米、千米每小时、千克等等

AVRational time_base;typedef struct AVRational{int num; ///< Numeratorint den; ///< Denominator
} AVRational;

从AVRational 的定义中我们可以看到这个时间使用分数来表示的，只有使用相同的时间基，计算出来的时间才有对比的意义。

不管是从设备采集信息保存到文件，还是一个文件播放出图像。都会有这样几个过程

1、mux/demux（分装/解封装）

2、codec/decode（bian/解码）

3、Raw data （YUV/PCM源数据）

每个过程向另一个过程转换，都需要转换这个time_base。

video显示线程内等待audio的代码

video_pts *= av_q2d(is->video_st->time_base);
video_pts = synchronize_video(is, pFrame, video_pts);while(1)
{//audio_clock时间再audio线程里播放，更新这个时间audio_pts = is->audio_clock;if (video_pts <= audio_pts) break;int delayTime = (video_pts - audio_pts) * 1000;delayTime = delayTime > 5 ? 5:delayTime;SDL_Delay(delayTime);
}

audio线程计算 audio_clock的代码

//基本思路是根据当前音频的声道数，采样位数，采样率，还有本次copy的数据大小，来计算播放玩buffer内数据的时间（这个时间不是很准确）
n = is->audioFrame->channels * is->audio_st->codec->channels;
is->audio_clock += (double) len1 / (double) (n * is->audio_st->codec->sample_rate);//time = bufsize /（声道数 * 采样位数 * 采样率）
//（声道数 * 采样位数 * 采样率）这一块可以理解为一秒钟可以播放的数据的大小

完整的代码

/* *************************************************************************       Filename:  sync_play.c*    Description:  *        Version:  1.0*        Created:  2020年07月08日 22时12分10秒*       Revision:  none*       Compiler:  gcc*         Author:  YOUR NAME (), *        Company:  * ************************************************************************/
#ifdef __cplusplus
extern "C"
{
#endif#include <libavcodec/avcodec.h>#include <libavformat/avformat.h>#include <libavutil/pixfmt.h>#include <libswscale/swscale.h>#include <SDL.h>#include <SDL_audio.h>#include <SDL_types.h>#include <SDL_name.h>#include <SDL_main.h>#include <SDL_config.h>#include <SDL2/SDL_thread.h>
#ifdef __cplusplus
};
#endif
#include <stdio.h>//Refresh
#define SFM_REFRESH_EVENT  (SDL_USEREVENT + 1)
//audio play end
#define SFM_AUDIOEND_EVENT  (SDL_USEREVENT + 1)//先按照提供的acc文件播放，后续修改
#define SDL_AUDIO_BUFFER_SIZE 1024
#define AVCODEC_MAX_AUDIO_FRAME_SIZE 192000 // 1 second of 48khz 32bit audio
#define PLAY_REFRESH_TIME			10		//刷新时间间隔#define MAX_AUDIO_SIZE (25 * 16 * 1024)
#define MAX_VIDEO_SIZE (25 * 256 * 1024)typedef struct PacketQueue {AVPacketList *first_pkt, *last_pkt;		//首尾指针int nb_packets;				//包个数int size;					//队列大小SDL_mutex *mutex;				//队列互斥锁SDL_cond *cond;				//队列全局变量
} PacketQueue;typedef struct VideoState {AVFormatContext *VideoFormatCtx;AVCodecContext *aCodecCtx; //音频解码器AVCodecContext *vCodecCtx; //音频解码器AVFrame *audioFrame;// 解码音频过程中的使用缓存PacketQueue audioq; //音频队列	unsigned int audio_buf_size;unsigned int audio_buf_index;//AVPacket audio_pkt;uint8_t *audio_pkt_data;uint8_t *audio_pkt_size;uint8_t *audio_buf;// 做两个线程同步使用double audio_clock; ///音频时钟double video_clock; ///<pts of last decoded frame / predicted pts of next decoded frameAVStream *video_st; //视频流AVStream *audio_st; //音频流PacketQueue videoq;	//视频队列SDL_Thread *video_tid;  //视频线程idSDL_Thread *refresh_tid;  //视频刷新线程idSDL_AudioDeviceID audioID;	//audio模块打开的设备ID} VideoState;
//SDL播放回调
void audio_callback(void *userdata, Uint8 *stream, int len);
//播放流队列初始化
void packet_queue_init(PacketQueue *q);
//播放流添加入队列
int packet_queue_put(PacketQueue *q, AVPacket *pkt);
//播放流出队列
static int packet_queue_get(PacketQueue *q, AVPacket *pkt, int block);
//从流中解码音频数据
int audio_decode_frame(VideoState *is, uint8_t *audio_buf, int buf_size);
///显示视频帧
void Video_Display_To_Window(VideoState 		*is,			//video play 状态机   AVPacket 		*packet,		//包AVFrame 		*pFrame, 		//流AVFrame 		*pFrameYUV, 	//YUV流AVCodecContext 	*pCodecCtx,		//解码上下文SDL_Texture    	*bmp,			//显示句柄SDL_Renderer   	*renderer,		//渲染器句柄struct SwsContext *img_convert_ctx,//转码数据SDL_Rect 		rect			//显示区域);int sfp_refresh_thread(void *opaque);	//SDL新线程入口			//调整同步时间
static double synchronize_video(VideoState *is, AVFrame *src_frame, double pts);//音频处理
int audio_stream_component_open(VideoState *is, int stream_index);//视频播放线程
int video_play(void *arg);int thread_exit=0;// 分配解码过程中的使用缓存
//AVFrame* audioFrame = avcodec_alloc_frame();
AVFrame *audioFrame = NULL;
PacketQueue *audioq = NULL;
VideoState  is = {0};#undef main
int main(int argc, char *argv[])
{AVFormatContext	*pFormatCtx;				//视频上下文AVCodecContext	*pCodecCtx, *videoCodeCtx;				//解码上下文int				i, audioindex, videoindex;AVCodec			*pCodec, *videoCodec;		//解码器AVPacket 		*packet, *VideoPacket;			//打包的流数据AVFrame 		*FrameAudio, *FrameVideo, *FrameYUV;uint8_t* out_buffer;int numBytes;int wait_flag = 0;SDL_Event event; char *filename = "./test3.mp4";	//SDL threadif(1 == argc){printf("%s:%d parameter error \n", __func__, __LINE__);return -1;}audioFrame = av_frame_alloc();//==================固定的结构================start====================//1、注册所有的解码器av_register_all();//printf("%s -- %d\n", __func__, __LINE__);//2、分配空间pFormatCtx = avformat_alloc_context();//videoCodeCtx = avformat_alloc_context();//printf("%s -- %d\n", __func__, __LINE__);if(pFormatCtx){//3、打开文件if(avformat_open_input(&pFormatCtx, /*filename*/argv[1], NULL, NULL) != 0) //error{printf("Couldn't open input stream.\n");return -1;}}//dump 视频信息av_dump_format(pFormatCtx, 0, /*filename*/argv[1], 0);//4、检索视频流信息if(avformat_find_stream_info(pFormatCtx,NULL)<0){printf("Couldn't find stream information.\n");return -1;}//5、查找流位置audioindex = -1;videoindex = -1;for(i = 0; i < pFormatCtx->nb_streams; i ++){printf("cur type :%d\n", pFormatCtx->streams[i]->codec->codec_type);if(pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO){audioindex = i;}if((pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) && (videoindex < 0)){videoindex = i;}}if((videoindex < 0) && (audioindex < 0)){printf("not fine audio or video stream! \n");return -1;}	printf("audioindex:%d, videoindex:%d\n", audioindex, videoindex);//6、解码上下文pCodecCtx = pFormatCtx->streams[audioindex]->codec;videoCodeCtx = pFormatCtx->streams[videoindex]->codec;//7、、获取视频解码器pCodec=avcodec_find_decoder(pCodecCtx->codec_id);videoCodec = avcodec_find_decoder(videoCodeCtx->codec_id);if(pCodec==NULL){printf("Codec not found.\n");return -1;}//8、、打开解码器if(avcodec_open2(pCodecCtx, pCodec,NULL)<0){printf("Could not open audio codec.\n");return -1;}if(avcodec_open2(videoCodeCtx, videoCodec,NULL)<0){printf("Could not open video codec.\n");return -1;}
//======================固定的结构===========end====================//=================SDL=============start===========if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {  printf( "Could not initialize SDL - %s\n", SDL_GetError()); return -1;}//video statu initis.VideoFormatCtx = avformat_alloc_context();is.VideoFormatCtx = pFormatCtx;is.audioFrame 	= av_frame_alloc();is.aCodecCtx 		= pCodecCtx;is.vCodecCtx 		= videoCodeCtx;is.audio_buf = (uint8_t *)malloc((AVCODEC_MAX_AUDIO_FRAME_SIZE * 3) / 2);is.video_tid = SDL_CreateThread(video_play, "video_play", &is);is.audio_st = pFormatCtx->streams[audioindex];is.video_st = pFormatCtx->streams[videoindex];//printf("%s -- %d\n", __func__, __LINE__);///  打开SDL播放设备 - 结束
//=================SDL=============end=============//创建一个队列，并且初始化audio_stream_component_open(&is, audioindex);packet = av_packet_alloc();if(!packet){printf("Could not malloc packet.\n");return -1;}// Debug -- Beginprintf("比特率 %3d\n", pFormatCtx->bit_rate);printf("解码器名称 %s\n", pCodecCtx->codec->long_name);printf("time_base  %d \n", pCodecCtx->time_base);printf("声道数  %d \n", pCodecCtx->channels);printf("sample per second  %d \n", pCodecCtx->sample_rate);// Debug -- End//主线程。读取流到对应的队列。while(1){if((is.audioq.size > MAX_AUDIO_SIZE) || (is.videoq.size > MAX_VIDEO_SIZE)) {SDL_Delay(10);  //队列限制以下大小，防止一下读取太多的包，导致内存吃完continue;}if(av_read_frame(pFormatCtx, packet) < 0) //流已经读取完了{//Exit Threadthread_exit=1;break;}if(packet->stream_index == audioindex){packet_queue_put(&is.audioq, packet);//这里我们将数据存入队列 因此不调用 av_free_packet 释放}else if(packet->stream_index == videoindex) //display video stream{packet_queue_put(&is.videoq, packet);}else{// Free the packet that was allocated by av_read_frameav_free_packet(packet);}}printf("read finished!\n");wait_flag = 1;do{SDL_WaitEvent(&event);if(SFM_AUDIOEND_EVENT == event.type){printf("main thread wait audio thread exit!\n");wait_flag = 0;}}while(wait_flag);//等待ideo play线程退出SDL_WaitThread(is.video_tid, NULL);av_free(FrameAudio);avcodec_close(pCodecCtx);// Close the codecavformat_close_input(&pFormatCtx);// Close the video filereturn 0;
}void audio_callback(void *userdata, Uint8 *stream, int len)
{VideoState *is = (VideoState *)userdata;int len1, audio_data_size;int n = 0; if((NULL != is) && (NULL != stream))  //参数检查{int audio_buf_size = (AVCODEC_MAX_AUDIO_FRAME_SIZE * 3) / 2;/*   len是由SDL传入的SDL缓冲区的大小，如果这个缓冲未满，我们就一直往里填充数据 */while (len > 0) {/*  audio_buf_index 和 audio_buf_size 标示我们自己用来放置解码出来的数据的缓冲区，*//*   这些数据待copy到SDL缓冲区， 当audio_buf_index >= audio_buf_size的时候意味着我*//*   们的缓冲为空，没有数据可供copy，这时候需要调用audio_decode_frame来解码出更/*   多的桢数据 */if (is->audio_buf_index >= is->audio_buf_size) {audio_data_size = audio_decode_frame(is, is->audio_buf, audio_buf_size/*sizeof(audio_buf)*/);/* audio_data_size < 0 标示没能解码出数据，我们默认播放静音 */if (audio_data_size < 0) {/* silence */is->audio_buf_size = 1024;/* 清零，静音 */memset(is->audio_buf, 0, is->audio_buf_size);} else {is->audio_buf_size = audio_data_size;}is->audio_buf_index = 0;}/*  查看stream可用空间，决定一次copy多少数据，剩下的下次继续copy */len1 = is->audio_buf_size - is->audio_buf_index;if (len1 > len) {len1 = len;}//音频PTS暂时现这样写，坑了再改if(is->audio_st->codec){//n = 2 * is->audio_st->codec->channels;n = is->audioFrame->channels * is->audio_st->codec->channels;is->audio_clock += (double) len1 / (double) (n * is->audio_st->codec->sample_rate);}memcpy(stream, (uint8_t *) is->audio_buf + is->audio_buf_index, len1);len -= len1;stream += len1;is->audio_buf_index += len1;}}
}//初始化队列
void packet_queue_init(PacketQueue *q) 
{memset(q, 0, sizeof(PacketQueue));q->mutex = SDL_CreateMutex();q->cond = SDL_CreateCond();
}//数据进入到队列中
int packet_queue_put(PacketQueue *q, AVPacket *pkt)
{AVPacketList *pkt1;if (av_dup_packet(pkt) < 0) {return -1;}pkt1 = (AVPacketList*)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;elseq->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;
}//从队列中取走数据
static int packet_queue_get(PacketQueue *q, AVPacket *pkt, int block) 
{AVPacketList *pkt1;int ret;SDL_LockMutex(q->mutex);for (;;) {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;
}//解码流数据到
int audio_decode_frame(VideoState *is, uint8_t *audio_buf, int buf_size)
{static AVPacket *pkt;static uint8_t *audio_pkt_data = NULL;static int audio_pkt_size = 0;int len1, data_size;SDL_Event event;pkt = av_packet_alloc();for(;;){if(packet_queue_get(&is->audioq, pkt, 0/*1*/) < 0){return -1;}//printf("%s %d\n", __func__, __LINE__);is->audio_pkt_data = pkt->data;is->audio_pkt_size = pkt->size;if(is->audio_pkt_size <= 0){//向主线程发送音频播放完成的消息event.type = SFM_AUDIOEND_EVENT;SDL_PushEvent(&event);return 0;   //没有数据，直接返回}while(is->audio_pkt_size > 0){int got_picture;int ret = avcodec_decode_audio4( is->aCodecCtx, is->audioFrame, &got_picture, pkt);if( ret < 0 ) {printf("Error in decoding audio frame.\n");exit(0);}//printf("%s %d\n", __func__, __LINE__);if( got_picture ) {int in_samples = is->audioFrame->nb_samples;short *sample_buffer = (short*)malloc(is->audioFrame->nb_samples * 2 * 2);memset(sample_buffer, 0, is->audioFrame->nb_samples * 4);int i=0;float *inputChannel0 = (float*)(is->audioFrame->extended_data[0]);//printf("%s %d in_samples:%d \n", __func__, __LINE__, in_samples);// Mono  单声道if( is->audioFrame->channels == 1 ) {for( i=0; i<in_samples; i++ ) {float sample = *inputChannel0++;if( sample < -1.0f ) {sample = -1.0f;} else if( sample > 1.0f ) {sample = 1.0f;}sample_buffer[i] = (int16_t)(sample * 32767.0f);}} else { // Stereo  双声道float* inputChannel1 = (float*)(is->audioFrame->extended_data[1]);for( i=0; i<in_samples; i++) {sample_buffer[i*2] = (int16_t)((*inputChannel0++) * 32767.0f);sample_buffer[i*2+1] = (int16_t)((*inputChannel1++) * 32767.0f);}}memcpy(audio_buf,sample_buffer,in_samples*4);free(sample_buffer);}		is->audio_pkt_size -= ret;if (is->audioFrame->nb_samples <= 0){continue;}data_size = is->audioFrame->nb_samples * 4;return data_size;}if(pkt->data)av_free_packet(pkt);}
}///显示视频帧
void Video_Display_To_Window(VideoState 		*is,			//video play 状态机AVPacket 		*packet,		//包AVFrame 		*pFrame, 		//流AVFrame 		*pFrameYUV, 	//YUV流AVCodecContext 	*pCodecCtx,		//解码上下文SDL_Texture    	*bmp,			//显示句柄SDL_Renderer   	*renderer,		//渲染器句柄struct SwsContext *img_convert_ctx,//转码数据SDL_Rect 		rect			//显示区域)
{int got_picture;SDL_Rect DisplayRect = {0};int ret = 0;double video_pts = 0; //当前视频的ptsdouble audio_pts = 0; //音频ptsDisplayRect.x = rect.x;DisplayRect.y = rect.y;DisplayRect.w = rect.w;DisplayRect.h = rect.h;ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);if(ret < 0){printf("Decode Error.\n");return -1;}if (packet->dts == AV_NOPTS_VALUE && pFrame->opaque&& *(uint64_t*) pFrame->opaque != AV_NOPTS_VALUE){video_pts = *(uint64_t *) pFrame->opaque;}else if (packet->dts != AV_NOPTS_VALUE){video_pts = packet->dts;}else{video_pts = 0;}
#if 0printf("%s %d ！\n", __func__, __LINE__);printf("num:%d den:%d\n", is->video_st->time_base.num, is->video_st->time_base.den);printf("num:%d den:%d\n", is->aCodecCtx->time_base.num, is->aCodecCtx->time_base.den);video_pts *= av_q2d(is->video_st->time_base);printf("video_pts:%f ！\n", video_pts);video_pts = synchronize_video(is, pFrame, video_pts);printf("%s %d ！\n", __func__, __LINE__);printf("video_pts: %f, audio_pts:%f\n", video_pts, is->audio_clock);
#elsevideo_pts *= av_q2d(is->video_st->time_base);video_pts = synchronize_video(is, pFrame, video_pts);
#endifwhile(1){//audio_clock时间再audio线程里播放，更新这个时间audio_pts = is->audio_clock;if (video_pts <= audio_pts) break;int delayTime = (video_pts - audio_pts) * 1000;delayTime = delayTime > 5 ? 5:delayTime;SDL_Delay(delayTime);}if(got_picture){	 //printf("update texture to SDL widows!\n");sws_scale(img_convert_ctx,(uint8_t const * const *)pFrame->data,pFrame->linesize,0,pCodecCtx->height,pFrameYUV->data,pFrameYUV->linesize);////iPitch 计算yuv一行数据占的字节数SDL_UpdateTexture( bmp, &DisplayRect, pFrameYUV->data[0], pFrameYUV->linesize[0] );//SDL_UpdateYUVTexture(bmp, &rect, pFrameYUV->data[0], pFrameYUV->linesize[0], pFrameYUV->data[1], pFrameYUV->linesize[1], pFrameYUV->data[2], pFrameYUV->linesize[2]);SDL_RenderClear( renderer );SDL_RenderCopy( renderer, bmp, &DisplayRect, &DisplayRect );SDL_RenderPresent( renderer );}//av_free_packet(packet);
}//Thread
int sfp_refresh_thread(void *opaque)
{SDL_Event event;VideoState *is = (VideoState *)opaque;printf("%s %d refresh thread id:%d !\n", __func__, __LINE__, is->refresh_tid);//while (is->refresh_tid != 0) //先把消息发过去，播放线程在等消息do{event.type = SFM_REFRESH_EVENT;SDL_PushEvent(&event);//Wait x msSDL_Delay(PLAY_REFRESH_TIME);}while(is->refresh_tid != 0);return 0;
}//调整同步时间
static 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;
}//音频处理
int audio_stream_component_open(VideoState *is, int stream_index)
{AVFormatContext *ic = is->VideoFormatCtx;AVCodecContext *codecCtx;AVCodec *codec;SDL_AudioSpec wanted_spec, spec;int64_t wanted_channel_layout = 0;int wanted_nb_channels;/*  SDL支持的声道数为 1, 2, 4, 6 *//*  后面我们会使用这个数组来纠正不支持的声道数目 */const int next_nb_channels[] = { 0, 0, 1, 6, 2, 6, 4, 6 };if (stream_index < 0 || stream_index >= ic->nb_streams) {return -1;}printf("%s %d entry !\n", __func__, __LINE__);packet_queue_init(&is->audioq);  //初始化音频队列
#if 0wanted_spec.format = AUDIO_S16SYS; // 具体含义请查看“SDL宏定义”部分wanted_spec.silence = 0;            // 0指示静音wanted_spec.samples = SDL_AUDIO_BUFFER_SIZE;  // 自定义SDL缓冲区大小wanted_spec.callback = audio_callback;        // 音频解码的关键回调函数wanted_spec.userdata = is;                    // 传给上面回调函数的外带数据do{is->audioID = SDL_OpenAudioDevice(SDL_GetAudioDeviceName(0,0),0,&wanted_spec, &spec,0);printf("SDL_OpenAudio (%d channels): %s\n",wanted_spec.channels, SDL_GetError());wanted_spec.channels = next_nb_channels[FFMIN(7, wanted_spec.channels)];if (!wanted_spec.channels)	//逐个匹配频道{printf("No more channel combinations to tyu, audio open failed\n");
//            return -1;break;}}while(is->audioID == 0);SDL_PauseAudioDevice(is->audioID,0);
#endif#if 1///  打开SDL播放设备 - 开始SDL_LockAudio();wanted_spec.freq = is->aCodecCtx->sample_rate;wanted_spec.format = AUDIO_S16SYS;wanted_spec.channels = is->aCodecCtx->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;}SDL_UnlockAudio();SDL_PauseAudio(0); //开始播放
#endif
}//视频播放线程
int video_play(void *arg)
{//========SDL==========//SDL---------------------------int screen_w=0,screen_h=0;SDL_Window *screen; SDL_Renderer* sdlRenderer;SDL_Texture* sdlTexture;SDL_Rect sdlRect;int ret, got_picture;struct SwsContext *img_convert_ctx;SDL_Thread *refresh_tid;SDL_Event event; AVFrame 		*FrameVideo, *FrameYUV;int numBytes;uint8_t* out_buffer;AVPacket *packet;//=========SDL===end===VideoState *is = (VideoState *) arg;//初始化队列packet_queue_init(&is->videoq);printf("%s init video queue :%p\n", __func__, &is->videoq);//=============video====================FrameVideo = av_frame_alloc();FrameYUV = av_frame_alloc();printf("%s %d entry !\n", __func__, __LINE__);///解码后数据转成YUV420Pimg_convert_ctx = sws_getContext(is->vCodecCtx->width, is->vCodecCtx->height, is->vCodecCtx->pix_fmt, is->vCodecCtx->width, is->vCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);numBytes = avpicture_get_size(AV_PIX_FMT_YUV420P, is->vCodecCtx->width,is->vCodecCtx->height);out_buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));avpicture_fill((AVPicture *) FrameYUV, out_buffer, AV_PIX_FMT_YUV420P,is->vCodecCtx->width, is->vCodecCtx->height);//int y_size = is->vCodecCtx->width * is->vCodecCtx->height;//packet = (AVPacket *) malloc(sizeof(AVPacket)); //分配一个packet//av_new_packet(packet, y_size); //分配packet的数据packet = av_packet_alloc();screen_w = is->vCodecCtx->width;screen_h = is->vCodecCtx->height;printf("%s -- %d\n", __func__, __LINE__);if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {  printf( "Could not initialize SDL - %s\n", SDL_GetError()); return -1;} //SDL 2.0 Support for multiple windows//创建窗口screen = SDL_CreateWindow("Simplest ffmpeg player's Window", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,screen_w, screen_h,SDL_WINDOW_OPENGL);if(!screen) {  printf("SDL: could not create window - exiting:%s\n",SDL_GetError());  return -1;}//创建一个渲染器sdlRenderer = SDL_CreateRenderer(screen, -1, 0);  //IYUV: Y + U + V  (3 planes)//YV12: Y + V + U  (3 planes)sdlTexture = SDL_CreateTexture(sdlRenderer, SDL_PIXELFORMAT_IYUV, SDL_TEXTUREACCESS_STREAMING,is->vCodecCtx->width,is->vCodecCtx->height);  sdlRect.x=0;sdlRect.y=0;sdlRect.w=screen_w;sdlRect.h=screen_h;//================video===end===========//refresh_tid = SDL_CreateThread(sfp_refresh_thread, "play thread", NULL); //创建一个线程定时刷新is->refresh_tid = SDL_CreateThread(sfp_refresh_thread, "play thread", is); //创建一个线程定时刷新if(0 > is->refresh_tid){printf("video play create thread fail : %s\n", SDL_GetError());}while(1){//printf("%s %d loop\n", __func__, __LINE__);SDL_WaitEvent(&event);  //等待消息到来，再刷新//printf("%s %d\n", __func__, __LINE__);if(event.type==SFM_REFRESH_EVENT){//第三个参数改成0，会有这样的情况：当队列中刚好为空，还没来得及往队列中存包，导致播放器意外停止//如果改成1的话，会导致一直阻塞在读ideo pack中：SDL_CondWait(q->cond, q->mutex);if (packet_queue_get(&is->videoq, packet, 0) <= 0) {//printf("%s read pack end !\n", __func__);is->refresh_tid = 0;break;//队列里面没有数据了  读取完毕了}Video_Display_To_Window( 		is, packet,FrameVideo, FrameYUV,is->vCodecCtx, sdlTexture,sdlRenderer, img_convert_ctx,sdlRect);}}}