ffmpeg+sdl教程----编写一个简单的播放器7(处理快进快退命令)

这篇教程例子中的程序，让右方向按键为快进10秒，上方向按键为快进60秒，左方向按键为快退10秒，上方向按键为快退60秒，程序中的av_seek_frame函数可能是用错了，或者函数本身的问题导致按上和右都没反应;按左和下让画面暂停，声音在很短区间内不停播放，这时再按右和下才正常。

#include "stdafx.h"extern "C"{#include "libavformat/avformat.h"#include "libswscale/swscale.h"}#include <SDL.h>#include <SDL_thread.h>#pragma comment(lib, "avformat.lib")#pragma comment(lib, "swscale.lib")#pragma comment(lib, "avcodec.lib")#pragma comment(lib, "avdevice.lib")#pragma comment(lib, "sdl.lib")#pragma comment(lib, "avutil.lib")#pragma comment(lib, "avfilter.lib")#pragma comment(lib, "postproc.lib")#ifdef main#undef main /* Prevents SDL from overriding main() */#endif#include <stdio.h>#include <math.h>#define SDL_AUDIO_BUFFER_SIZE 1024#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 SAMPLE_CORRECTION_PERCENT_MAX 10#define AUDIO_DIFF_AVG_NB 20#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#define DEFAULT_AV_SYNC_TYPE AV_SYNC_EXTERNAL_MASTERenum{AV_SYNC_AUDIO_MASTER,AV_SYNC_VIDEO_MASTER,AV_SYNC_EXTERNAL_MASTER,};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;int             av_sync_type;double          external_clock; /* external clock base */int64_t         external_clock_time;int             seek_req;int             seek_flags;int64_t         seek_pos;double          audio_clock;AVStream        *audio_st;PacketQueue     audioq;uint8_t*        audio_buf;unsigned int    audio_buf_size;unsigned int    audio_buf_index;AVPacket        audio_pkt;uint8_taudio_pkt_size;//uint8_t         *audio_pkt_data;//int             audio_pkt_size;int             audio_hw_buf_size;double          audio_diff_cum; /* used for AV difference average computation */double          audio_diff_avg_coef;double          audio_diff_threshold;int             audio_diff_avg_count;double          frame_timer;double          frame_last_pts;double          frame_last_delay;double          video_clock; ///<pts of last decoded frame / predicted pts of next decoded framedouble          video_current_pts; ///<current displayed pts (different from video_clock if frame fifos are used)int64_t         video_current_pts_time;  ///<time (av_gettime) at which we updated video_current_pts - used to have running video ptsAVStream        *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;} VideoState;SDL_Surface     *screen;/* Since we only have one decoding thread, the Big Structcan be global in case we need it. */VideoState *global_video_state;AVPacket flush_pkt;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(pkt != &flush_pkt && 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;}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;}static void packet_queue_flush(PacketQueue *q){AVPacketList *pkt, *pkt1;SDL_LockMutex(q->mutex);for(pkt = q->first_pkt; pkt != NULL; pkt = pkt1){pkt1 = pkt->next;av_free_packet(&pkt->pkt);av_freep(&pkt);}q->last_pkt = NULL;q->first_pkt = NULL;q->nb_packets = 0;q->size = 0;SDL_UnlockMutex(q->mutex);}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;}double get_video_clock(VideoState *is){double delta;delta = (av_gettime() - is->video_current_pts_time) / 1000000.0;return is->video_current_pts + delta;}double get_external_clock(VideoState *is){return av_gettime() / 1000000.0;}double get_master_clock(VideoState *is){if(is->av_sync_type == AV_SYNC_VIDEO_MASTER){return get_video_clock(is);}else if(is->av_sync_type == AV_SYNC_AUDIO_MASTER){return get_audio_clock(is);}else{return get_external_clock(is);}}/* Add or subtract samples to get a better sync, return newaudio buffer size */int synchronize_audio(VideoState *is, short *samples,int samples_size, double pts){int n;double ref_clock;n = 2 * is->audio_st->codec->channels;if(is->av_sync_type != AV_SYNC_AUDIO_MASTER){double diff, avg_diff;int wanted_size, min_size, max_size, nb_samples;ref_clock = get_master_clock(is);diff = get_audio_clock(is) - ref_clock;if(diff < AV_NOSYNC_THRESHOLD){// accumulate the diffsis->audio_diff_cum = diff + is->audio_diff_avg_coef* is->audio_diff_cum;if(is->audio_diff_avg_count < AUDIO_DIFF_AVG_NB){is->audio_diff_avg_count++;}else{avg_diff = is->audio_diff_cum * (1.0 - is->audio_diff_avg_coef);if(fabs(avg_diff) >= is->audio_diff_threshold){wanted_size = samples_size + ((int)(diff * is->audio_st->codec->sample_rate) * n);min_size = samples_size * ((100 - SAMPLE_CORRECTION_PERCENT_MAX) / 100);max_size = samples_size * ((100 + SAMPLE_CORRECTION_PERCENT_MAX) / 100);if(wanted_size < min_size){wanted_size = min_size;}else if (wanted_size > max_size){wanted_size = max_size;}if(wanted_size < samples_size){/* remove samples */samples_size = wanted_size;}else if(wanted_size > samples_size){uint8_t *samples_end, *q;int nb;/* add samples by copying final sample*/nb = (samples_size - wanted_size);samples_end = (uint8_t *)samples + samples_size - n;q = samples_end + n;while(nb > 0){memcpy(q, samples_end, n);q += n;nb -= n;}samples_size = wanted_size;}}}}else{/* difference is TOO big; reset diff stuff */is->audio_diff_avg_count = 0;is->audio_diff_cum = 0;}}return samples_size;}int audio_decode_frame(VideoState *is, uint8_t *audio_buf, int buf_size, double *pts_ptr){int len1, data_size, n;AVPacket *pkt = &is->audio_pkt;double pts;for(;;){while(pkt->size > 0){data_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;len1 = avcodec_decode_audio3(is->audio_st->codec,(int16_t *)audio_buf, &data_size,pkt);if(len1 < 0){/* if error, skip frame */pkt->size = 0;is->audio_pkt_size = 0;break;}pkt->data += len1;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){pkt->data -= (is->audio_pkt_size - pkt->size);av_free_packet(pkt);}if(is->quit){return -1;}/* next packet */if(packet_queue_get(&is->audioq, pkt, 1) < 0){is->audio_pkt_size = 0;return -1;}is->audio_pkt_size = pkt->size;if(pkt->data == flush_pkt.data){avcodec_flush_buffers(is->audio_st->codec);continue;}/* 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, is->audio_buf, sizeof(is->audio_buf), &pts);if(audio_size < 0){/* If error, output silence */is->audio_buf_size = 1024;memset(is->audio_buf, 0, is->audio_buf_size);}else{audio_size = synchronize_audio(is, (int16_t *)is->audio_buf,audio_size, pts);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){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)(h * aspect_ratio)) & -3;if(w > screen->w){w = screen->w;h = ((int)(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){schedule_refresh(is, 1);}else{vp = &is->pictq[is->pictq_rindex];is->video_current_pts = vp->pts;is->video_current_pts_time = av_gettime();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_master_clock(is);diff = vp->pts - ref_clock;/* Skip or repeat the frame. Take delay into accountFFPlay still doesn't "know if this is the best guess." */if(is->av_sync_type != AV_SYNC_VIDEO_MASTER){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/smallerSDL_FreeYUVOverlay(vp->bmp);}// Allocate a place to put our YUV image on that screenvp->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;//int dst_pix_fmt;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 initiallyvp = &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 nullbut still return vp->allocated = 1? */static struct SwsContext *img_convert_ctx;if (img_convert_ctx == NULL){img_convert_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_BICUBIC, NULL, NULL, NULL);if (img_convert_ctx == NULL){fprintf(stderr, "Cannot initialize the conversion context/n");exit(1);}}if(vp->bmp){SDL_LockYUVOverlay(vp->bmp);//dst_pix_fmt = PIX_FMT_YUV420P;/* 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/*img_convert(&pict, dst_pix_fmt,(AVPicture *)pFrame, is->video_st->codec->pix_fmt,is->video_st->codec->width, is->video_st->codec->height);*/sws_scale(img_convert_ctx, 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 = (uint64_t *)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 len1, frameFinished;AVFrame *pFrame;double pts;pFrame = avcodec_alloc_frame();for(;;){if(packet_queue_get(&is->videoq, packet, 1) < 0){// means we quit getting packetsbreak;}pts = 0;// Save global pts to be stored in pFrame in first callglobal_video_pkt_pts = packet->pts;// Decode video framelen1 = 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;AVCodec *codec;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 streamcodecCtx = pFormatCtx->streams[stream_index]->codec;if(codecCtx->codec_type == AVMEDIA_TYPE_AUDIO){// Set audio settings from codec infowanted_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_open(codecCtx, codec) < 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);is->audio_buf = (uint8_t *)av_malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE * 3 / 2);is->audio_pkt_size = 0;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;is->video_current_pts_time = av_gettime();packet_queue_init(&is->videoq);is->video_tid = SDL_CreateThread(video_thread, is);codecCtx->get_buffer = our_get_buffer;codecCtx->release_buffer = our_release_buffer;break;default:break;}return 0;}int decode_interrupt_cb(void){return (global_video_state && global_video_state->quit);}int decode_thread(void *arg){VideoState *is = (VideoState *)arg;AVFormatContext *pFormatCtx;AVPacket pkt1, *packet = &pkt1;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!url_set_interrupt_cb(decode_interrupt_cb);// Open video fileif(av_open_input_file(&pFormatCtx, is->filename, NULL, 0, NULL)!=0)return -1; // Couldn't open fileis->pFormatCtx = pFormatCtx;// Retrieve stream informationif(av_find_stream_info(pFormatCtx)<0)return -1; // Couldn't find stream information// Dump information about file onto standard errordump_format(pFormatCtx, 0, is->filename, 0);// Find the first video streamfor(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 loopav_init_packet(&flush_pkt);flush_pkt.data = (uint8_t *)"FLUSH";for(;;){if(is->quit){break;}// seek stuff goes hereif(is->seek_req){int stream_index= -1;int64_t seek_target = is->seek_pos;if(is->videoStream >= 0)stream_index = is->videoStream;else if(is->audioStream >= 0)stream_index = is->audioStream;if(stream_index>=0){AVRational base_q;base_q.den = 1;base_q.num = AV_TIME_BASE;seek_target = av_rescale_q(seek_target, base_q,pFormatCtx->streams[stream_index]->time_base);}if(!av_seek_frame(is->pFormatCtx, stream_index, seek_target, is->seek_flags)){fprintf(stderr, "%s: error while seeking/n", is->pFormatCtx->filename);}else{if(is->audioStream >= 0){packet_queue_flush(&is->audioq);//packet_queue_put(&is->audioq, &flush_pkt);}if(is->videoStream >= 0){packet_queue_flush(&is->videoq);//packet_queue_put(&is->videoq, &flush_pkt);}}is->seek_req = 0;printf("av_seek_frame called/n");}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(url_ferror(pFormatCtx->pb) == 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;}void stream_seek(VideoState *is, int64_t pos, int rel){if(!is->seek_req){is->seek_pos = pos;is->seek_flags = rel < 0 ? AVSEEK_FLAG_BACKWARD : AVSEEK_FLAG_BYTE;is->seek_req = 1;}}int main(int argc, char *argv[]){SDL_Event       event;VideoState      *is;is = (VideoState *)av_mallocz(sizeof(VideoState));//if(argc < 2)//{//fprintf(stderr, "Usage: test <file>/n");//exit(1);//}//argv[1] = "c:\\b frame 24.mp4";argv[1] = "c:\\640x480_sound.mp4";// Register all formats and codecsav_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);#elsescreen = SDL_SetVideoMode(640, 480, 24, 0);#endifif(!screen){fprintf(stderr, "SDL: could not set video mode - exiting/n");exit(1);}//pstrcpy(is->filename, sizeof(is->filename), argv[1]);strcpy(is->filename,argv[1]);is->pictq_mutex = SDL_CreateMutex();is->pictq_cond = SDL_CreateCond();schedule_refresh(is, 40);//is->av_sync_type = DEFAULT_AV_SYNC_TYPE;is->av_sync_type = AV_SYNC_AUDIO_MASTER;is->parse_tid = SDL_CreateThread(decode_thread, is);if(!is->parse_tid){av_free(is);return -1;}for(;;){double incr, pos;SDL_WaitEvent(&event);switch(event.type){case SDL_KEYDOWN:switch(event.key.keysym.sym){case SDLK_LEFT:incr = -10.0;goto do_seek;case SDLK_RIGHT:incr = 10.0;goto do_seek;case SDLK_UP:incr = 60.0;goto do_seek;case SDLK_DOWN:incr = -60.0;goto do_seek;do_seek:if(global_video_state){pos = get_master_clock(global_video_state);pos += incr;stream_seek(global_video_state, (int64_t)(pos * AV_TIME_BASE), incr);}break;default:break;}break;case FF_QUIT_EVENT:case SDL_QUIT:is->quit = 1;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;}

     

转自 http://blog.csdn.net/mu399/article/details/5818970