tutorial07.c

// tutorial07.c
// A pedagogical video player that really works! Now with seeking features.
//
// Code based on FFplay, Copyright (c) 2003 Fabrice Bellard,
// and a tutorial by Martin Bohme (boehme@inb.uni-luebeckREMOVETHIS.de)
// Tested on Gentoo, CVS version 5/01/07 compiled with GCC 4.1.1
// Use
//
// gcc -o tutorial07 tutorial07.c -lavformat -lavcodec -lz -lm `sdl-config --cflags --libs`
// to build (assuming libavformat and libavcodec are correctly installed,
// and assuming you have sdl-config. Please refer to SDL docs for your installation.)
//
// Run using
// tutorial07 myvideofile.mpg
//
// to play the video.

#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <libavformat/avio.h>
#include <libavutil/avstring.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_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_VIDEO_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[(AVCODEC_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          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 frame
    double          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 pts
    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;
} VideoState;

enum {
    AV_SYNC_AUDIO_MASTER,
    AV_SYNC_VIDEO_MASTER,
    AV_SYNC_EXTERNAL_MASTER,
};

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;
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 = 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;
}
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 *vidState) {
    double pts;
    int hw_buf_size, bytes_per_sec, n;
    
    pts = vidState->audio_clock; /* maintained in the audio thread */
    hw_buf_size = vidState->audio_buf_size - vidState->audio_buf_index;
    bytes_per_sec = 0;
    n = vidState->audio_st->codec->channels * 2;
    if(vidState->audio_st) {
        bytes_per_sec = vidState->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 *vidState) {
    double delta;
    
    delta = (av_gettime() - vidState->video_current_pts_time) / 1000000.0;
    return vidState->video_current_pts + delta;
}
double get_external_clock(VideoState *vidState) {
    return av_gettime() / 1000000.0;
}
double get_master_clock(VideoState *vidState) {
    if(vidState->av_sync_type == AV_SYNC_VIDEO_MASTER) {
        return get_video_clock(vidState);
    } else if(vidState->av_sync_type == AV_SYNC_AUDIO_MASTER) {
        return get_audio_clock(vidState);
    } else {
        return get_external_clock(vidState);
    }
}
/* Add or subtract samples to get a better sync, return new
 audio buffer size */
int synchronize_audio(VideoState *vidState, short *samples,
                      int samples_size, double pts) {
    int n;
    double ref_clock;
    
    n = 2 * vidState->audio_st->codec->channels;
    
    if(vidState->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(vidState);
        diff = get_audio_clock(vidState) - ref_clock;
        
        if(diff < AV_NOSYNC_THRESHOLD) {
            // accumulate the diffs
            vidState->audio_diff_cum = diff + vidState->audio_diff_avg_coef
            * vidState->audio_diff_cum;
            if(vidState->audio_diff_avg_count < AUDIO_DIFF_AVG_NB) {
                vidState->audio_diff_avg_count++;
            } else {
                avg_diff = vidState->audio_diff_cum * (1.0 - vidState->audio_diff_avg_coef);
                if(fabs(avg_diff) >= vidState->audio_diff_threshold) {
                    wanted_size = samples_size + ((int)(diff * vidState->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 vidState TOO big; reset diff stuff */
            vidState->audio_diff_avg_count = 0;
            vidState->audio_diff_cum = 0;
        }
    }
    return samples_size;
}

int audio_decode_frame(VideoState *vidState, uint8_t *audio_buf, int buf_size, double *pts_ptr) {
    
    int len1, data_size, n;
    AVPacket *pkt = &vidState->audio_pkt;
    static AVPacket pktTemp;
    double pts;
    static AVFrame *decoded_aframe;
    
    for(;;) {
        while(vidState->audio_pkt_size > 0) {
            int got_frame = 0;
            if (!decoded_aframe) {
                if (!(decoded_aframe = avcodec_alloc_frame())) {
                    fprintf(stderr, "out of memory\n");
                    exit(1);
                }
            } else
                avcodec_get_frame_defaults(decoded_aframe);
            data_size = buf_size;
            len1 = avcodec_decode_audio4(vidState->audio_st->codec, decoded_aframe, &got_frame, &pktTemp);
            
            if(len1 < 0) {
                /* if error, skip frame */
                vidState->audio_pkt_size = 0;
                break;
            }
            
            if (got_frame) {
                //printf("\nGot frame!");
                //printf("\nFrame data size: %d", sizeof(decoded_aframe->data[0]));
                data_size = av_samples_get_buffer_size(NULL, vidState->audio_st->codec->channels,
                                                       decoded_aframe->nb_samples,
                                                       vidState->audio_st->codec->sample_fmt, 1);
                if (data_size > buf_size) {
                    data_size = buf_size;
                }
                memcpy(audio_buf, decoded_aframe->data[0], data_size);
                
            }else{
                data_size = 0;
            }
            pktTemp.data += len1;
            pktTemp.size -= len1;
            vidState->audio_pkt_data += len1;
            vidState->audio_pkt_size -= len1;
            if(data_size <= 0) {
                /* No data yet, get more frames */
                continue;
            }
            pts = vidState->audio_clock;
            *pts_ptr = pts;
            n = 2 * vidState->audio_st->codec->channels;
            vidState->audio_clock += (double)data_size /
            (double)(n * vidState->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(vidState->quit) {
            return -1;
        }
        /* next packet */
        if(packet_queue_get(&vidState->audioq, pkt, 1) < 0) {
            return -1;
        }
        if(pkt->data == flush_pkt.data) {
            avcodec_flush_buffers(vidState->audio_st->codec);
            continue;
        }
        pktTemp.data = pkt->data;
        pktTemp.size = pkt->size;
        vidState->audio_pkt_data = pkt->data;
        vidState->audio_pkt_size = pkt->size;
        /* if update, update the audio clock w/pts */
        if(pkt->pts != AV_NOPTS_VALUE) {
            vidState->audio_clock = av_q2d(vidState->audio_st->time_base)*pkt->pts;
        }
    }
}

void audio_callback(void *userdata, Uint8 *stream, int len) {
    
    VideoState *vidState = (VideoState *)userdata;
    int len1, audio_size;
    double pts;
    
    while(len > 0) {
        if(vidState->audio_buf_index >= vidState->audio_buf_size) {
            /* We have already sent all our data; get more */
            audio_size = audio_decode_frame(vidState, vidState->audio_buf, sizeof(vidState->audio_buf), &pts);
            if(audio_size < 0) {
                /* If error, output silence */
                vidState->audio_buf_size = 1024;
                memset(vidState->audio_buf, 0, vidState->audio_buf_size);
            } else {
                audio_size = synchronize_audio(vidState, (int16_t *)vidState->audio_buf,
                                               audio_size, pts);
                vidState->audio_buf_size = audio_size;
            }
            vidState->audio_buf_index = 0;
        }
        len1 = vidState->audio_buf_size - vidState->audio_buf_index;
        if(len1 > len)
            len1 = len;
        memcpy(stream, (uint8_t *)vidState->audio_buf + vidState->audio_buf_index, len1);
        len -= len1;
        stream += len1;
        vidState->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 *vidState, int delay) {
    SDL_AddTimer(delay, sdl_refresh_timer_cb, vidState);
}

void video_display(VideoState *vidState) {
    
    SDL_Rect rect;
    VideoPicture *vp;
    AVPicture pict;
    float aspect_ratio;
    int w, h, x, y;
    int i;
    
    vp = &vidState->pictq[vidState->pictq_rindex];
    if(vp->bmp) {
        if(vidState->video_st->codec->sample_aspect_ratio.num == 0) {
            aspect_ratio = 0;
        } else {
            aspect_ratio = av_q2d(vidState->video_st->codec->sample_aspect_ratio) *
            vidState->video_st->codec->width / vidState->video_st->codec->height;
        }
        if(aspect_ratio <= 0.0) {
            aspect_ratio = (float)vidState->video_st->codec->width /
            (float)vidState->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 *vidState = (VideoState *)userdata;
    VideoPicture *vp;
    double actual_delay, delay, sync_threshold, ref_clock, diff;
    
    if(vidState->video_st) {
        if(vidState->pictq_size == 0) {
            schedule_refresh(vidState, 1);
        } else {
            vp = &vidState->pictq[vidState->pictq_rindex];
            
            vidState->video_current_pts = vp->pts;
            vidState->video_current_pts_time = av_gettime();
            
            delay = vp->pts - vidState->frame_last_pts; /* the pts from last time */
            if(delay <= 0 || delay >= 1.0) {
                /* if incorrect delay, use previous one */
                delay = vidState->frame_last_delay;
            }
            /* save for next time */
            vidState->frame_last_delay = delay;
            vidState->frame_last_pts = vp->pts;
            
            /* update delay to sync to audio if not master source */
            if(vidState->av_sync_type != AV_SYNC_VIDEO_MASTER) {
                ref_clock = get_master_clock(vidState);
                diff = vp->pts - ref_clock;
                
                /* Skip or repeat the frame. Take delay into account
                 FFPlay still doesn't "know if this vidState 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;
                    }
                }
            }
            
            vidState->frame_timer += delay;
            /* computer the REAL delay */
            actual_delay = vidState->frame_timer - (av_gettime() / 1000000.0);
            if(actual_delay < 0.010) {
                /* Really it should skip the picture instead */
                actual_delay = 0.010;
            }
            schedule_refresh(vidState, (int)(actual_delay * 1000 + 0.5));
            
            /* show the picture! */
            video_display(vidState);
            
            /* update queue for next picture! */
            if(++vidState->pictq_rindex == VIDEO_PICTURE_QUEUE_SIZE) {
                vidState->pictq_rindex = 0;
            }
            SDL_LockMutex(vidState->pictq_mutex);
            vidState->pictq_size--;
            SDL_CondSignal(vidState->pictq_cond);
            SDL_UnlockMutex(vidState->pictq_mutex);
        }
    } else {
        schedule_refresh(vidState, 100);
    }
}

void alloc_picture(void *userdata) {
    
    VideoState *vidState = (VideoState *)userdata;
    VideoPicture *vp;
    
    vp = &vidState->pictq[vidState->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(vidState->video_st->codec->width,
                                   vidState->video_st->codec->height,
                                   SDL_YV12_OVERLAY,
                                   screen);
    vp->width = vidState->video_st->codec->width;
    vp->height = vidState->video_st->codec->height;
    
    SDL_LockMutex(vidState->pictq_mutex);
    vp->allocated = 1;
    SDL_CondSignal(vidState->pictq_cond);
    SDL_UnlockMutex(vidState->pictq_mutex);
    
}

int queue_picture(VideoState *vidState, AVFrame *pFrame, double pts) {
    
    VideoPicture *vp;
    int dst_pix_fmt;
    AVPicture pict;
    
    /* wait until we have space for a new pic */
    SDL_LockMutex(vidState->pictq_mutex);
    while(vidState->pictq_size >= VIDEO_PICTURE_QUEUE_SIZE &&
          !vidState->quit) {
        SDL_CondWait(vidState->pictq_cond, vidState->pictq_mutex);
    }
    SDL_UnlockMutex(vidState->pictq_mutex);
    
    if(vidState->quit)
        return -1;
    
    // windex vidState set to 0 initially
    vp = &vidState->pictq[vidState->pictq_windex];
    
    /* allocate or resize the buffer! */
    if(!vp->bmp ||
       vp->width != vidState->video_st->codec->width ||
       vp->height != vidState->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 = vidState;
        SDL_PushEvent(&event);
        
        /* wait until we have a picture allocated */
        SDL_LockMutex(vidState->pictq_mutex);
        while(!vp->allocated && !vidState->quit) {
            SDL_CondWait(vidState->pictq_cond, vidState->pictq_mutex);
        }
        SDL_UnlockMutex(vidState->pictq_mutex);
        if(vidState->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);
        
        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
        static struct SwsContext *img_convert_ctx;
        int w = vidState->video_st->codec->width;
        int h = vidState->video_st->codec->height;
        if (!img_convert_ctx)
            img_convert_ctx = sws_getContext(w, h, vidState->video_st->codec->pix_fmt,
                                         w, h, dst_pix_fmt,
                                         SWS_X, NULL, NULL, NULL);
        
        sws_scale(img_convert_ctx, (const uint8_t * const *)pFrame->data,
                  pFrame->linesize, 0, h,
                  pict.data, pict.linesize);
        SDL_UnlockYUVOverlay(vp->bmp);
        vp->pts = pts;
        
        /* now we inform our display thread that we have a pic ready */
        if(++vidState->pictq_windex == VIDEO_PICTURE_QUEUE_SIZE) {
            vidState->pictq_windex = 0;
        }
        SDL_LockMutex(vidState->pictq_mutex);
        vidState->pictq_size++;
        SDL_UnlockMutex(vidState->pictq_mutex);
    }
    return 0;
}

double synchronize_video(VideoState *vidState, AVFrame *src_frame, double pts) {
    
    double frame_delay;
    
    if(pts != 0) {
        /* if we have pts, set video clock to it */
        vidState->video_clock = pts;
    } else {
        /* if we aren't given a pts, set it to the clock */
        pts = vidState->video_clock;
    }
    /* update the video clock */
    frame_delay = av_q2d(vidState->video_st->codec->time_base);
    /* if we are repeating a frame, adjust clock accordingly */
    frame_delay += src_frame->repeat_pict * (frame_delay * 0.5);
    vidState->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 vidState 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 *vidState = (VideoState *)arg;
    AVPacket pkt1, *packet = &pkt1;
    int len1, frameFinished;
    AVFrame *pFrame;
    double pts;
    
    pFrame = avcodec_alloc_frame();
    
    for(;;) {
        if(packet_queue_get(&vidState->videoq, packet, 1) < 0) {
            // means we quit getting packets
            break;
        }
        if(packet->data == flush_pkt.data) {
            avcodec_flush_buffers(vidState->video_st->codec);
            continue;
        }
        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(vidState->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(vidState->video_st->time_base);
        
        // Did we get a video frame?
        if(frameFinished) {
            pts = synchronize_video(vidState, pFrame, pts);
            if(queue_picture(vidState, pFrame, pts) < 0) {
                break;
            }
        }
        av_free_packet(packet);
    }
    av_free(pFrame);
    return 0;
}
int stream_component_open(VideoState *vidState, int stream_index) {
    
    AVFormatContext *pFormatCtx = vidState->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 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 = vidState;
        
        if(SDL_OpenAudio(&wanted_spec, &spec) < 0) {
            fprintf(stderr, "SDL_OpenAudio: %s\n", SDL_GetError());
            return -1;
        }
        vidState->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:
            vidState->audioStream = stream_index;
            vidState->audio_st = pFormatCtx->streams[stream_index];
            vidState->audio_buf_size = 0;
            vidState->audio_buf_index = 0;
            
            /* averaging filter for audio sync */
            vidState->audio_diff_avg_coef = exp(log(0.01 / AUDIO_DIFF_AVG_NB));
            vidState->audio_diff_avg_count = 0;
            /* Correct audio only if larger error than this */
            vidState->audio_diff_threshold = 2.0 * SDL_AUDIO_BUFFER_SIZE / codecCtx->sample_rate;
            
            memset(&vidState->audio_pkt, 0, sizeof(vidState->audio_pkt));
            packet_queue_init(&vidState->audioq);
            SDL_PauseAudio(0);
            break;
        case AVMEDIA_TYPE_VIDEO:
            vidState->videoStream = stream_index;
            vidState->video_st = pFormatCtx->streams[stream_index];
            
            vidState->frame_timer = (double)av_gettime() / 1000000.0;
            vidState->frame_last_delay = 40e-3;
            vidState->video_current_pts_time = av_gettime();
            
            packet_queue_init(&vidState->videoq);
            vidState->video_tid = SDL_CreateThread(video_thread, vidState);
            codecCtx->get_buffer = our_get_buffer;
            codecCtx->release_buffer = our_release_buffer;
            
            break;
        default:
            break;
    }
    
    
}

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

const AVIOInterruptCB int_cb = { decode_interrupt_cb, NULL };

int decode_thread(void *arg) {
    
    VideoState *vidState = (VideoState *)arg;
    AVFormatContext *pFormatCtx;
    AVPacket pkt1, *packet = &pkt1;
    
    int video_index = -1;
    int audio_index = -1;
    int i;
    
    vidState->videoStream=-1;
    vidState->audioStream=-1;
    
    global_video_state = vidState;

    pFormatCtx = avformat_alloc_context();
    pFormatCtx->interrupt_callback = int_cb;
    
    if (avio_open2(&pFormatCtx->pb, vidState->filename, AVIO_FLAG_READ, &pFormatCtx->interrupt_callback, NULL))
        return -1;
    
    // Open video file
    if (avformat_open_input(&pFormatCtx, vidState->filename, NULL, NULL)!=0)
        return -1; // Couldn't open file
    
    vidState->pFormatCtx = pFormatCtx;
    
    // Retrieve stream information
    if(avformat_find_stream_info(pFormatCtx, NULL)<0)
        return -1; // Couldn't find stream information
    
    // Dump information about file onto standard error
    av_dump_format(pFormatCtx, 0, vidState->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(vidState, audio_index);
    }
    if(video_index >= 0) {
        stream_component_open(vidState, video_index);
    }
    
    if(vidState->videoStream < 0 || vidState->audioStream < 0) {
        fprintf(stderr, "%s: could not open codecs\n", vidState->filename);
        goto fail;
    }
    
    // main decode loop
    
    for(;;) {
        if(vidState->quit) {
            break;
        }
        // seek stuff goes here
        if(vidState->seek_req) {
            int stream_index= -1;
            int64_t seek_target = vidState->seek_pos;
            
            if     (vidState->videoStream >= 0) stream_index = vidState->videoStream;
            else if(vidState->audioStream >= 0) stream_index = vidState->audioStream;
            
            if(stream_index>=0){
                seek_target= av_rescale_q(seek_target, AV_TIME_BASE_Q, pFormatCtx->streams[stream_index]->time_base);
            }
            if(!av_seek_frame(vidState->pFormatCtx, stream_index, seek_target, vidState->seek_flags)) {
                fprintf(stderr, "%s: error while seeking\n", vidState->pFormatCtx->filename);
            } else {
                if(vidState->audioStream >= 0) {
                    packet_queue_flush(&vidState->audioq);
                    packet_queue_put(&vidState->audioq, &flush_pkt);
                }
                if(vidState->videoStream >= 0) {
                    packet_queue_flush(&vidState->videoq);
                    packet_queue_put(&vidState->videoq, &flush_pkt);
                }
            }
            vidState->seek_req = 0;
        }
        
        if(vidState->audioq.size > MAX_AUDIOQ_SIZE ||
           vidState->videoq.size > MAX_VIDEOQ_SIZE) {
            SDL_Delay(10);
            continue;
        }
        if(av_read_frame(vidState->pFormatCtx, packet) < 0) {
            //if(url_ferror(&pFormatCtx->pb) == 0) {
            if(&pFormatCtx->pb && &pFormatCtx->pb->error){
                SDL_Delay(100); /* no error; wait for user input */
                continue;
            } else {
                break;
            }
        }
        // Is this a packet from the video stream?
        if(packet->stream_index == vidState->videoStream) {
            packet_queue_put(&vidState->videoq, packet);
        } else if(packet->stream_index == vidState->audioStream) {
            packet_queue_put(&vidState->audioq, packet);
        } else {
            av_free_packet(packet);
        }
    }
    /* all done - wait for it */
    while(!vidState->quit) {
        SDL_Delay(100);
    }
fail:
    {
        SDL_Event event;
        event.type = FF_QUIT_EVENT;
        event.user.data1 = vidState;
        SDL_PushEvent(&event);
    }
    return 0;
}

void stream_seek(VideoState *vidState, int64_t pos, int rel) {
    
    if(!vidState->seek_req) {
        vidState->seek_pos = pos;
        vidState->seek_flags = rel < 0 ? AVSEEK_FLAG_BACKWARD : 0;
        vidState->seek_req = 1;
    }
}
int main(int argc, char *argv[]) {
    
    SDL_Event       event;
    double          pts;
    VideoState      *vidState;
    
    vidState = 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(vidState->filename, argv[1], sizeof(vidState->filename));
    
    vidState->pictq_mutex = SDL_CreateMutex();
    vidState->pictq_cond = SDL_CreateCond();
    
    schedule_refresh(vidState, 40);
    
    vidState->av_sync_type = DEFAULT_AV_SYNC_TYPE;
    vidState->parse_tid = SDL_CreateThread(decode_thread, vidState);
    if(!vidState->parse_tid) {
        av_free(vidState);
        return -1;
    }
    
    av_init_packet(&flush_pkt);
    flush_pkt.data = "FLUSH";
    
    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:
                vidState->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;
}