1、ffplay音视频同步的选项参数：sync=audio/video/ext
static int av_sync_type = AV_SYNC_AUDIO_MASTER; //默认音频
static int opt_sync(void *optctx, const char *opt, const char *arg)
{
if (!strcmp(arg, "audio")) //音频
av_sync_type = AV_SYNC_AUDIO_MASTER;
else if (!strcmp(arg, "video")) //视频
av_sync_type = AV_SYNC_VIDEO_MASTER;
else if (!strcmp(arg, "ext")) //外部时间
av_sync_type = AV_SYNC_EXTERNAL_CLOCK;
else {
av_log(NULL, AV_LOG_ERROR, "Unknown value for %s: %s\n", opt, arg);
exit(1);
}
return 0;
}2、以视频或者外部时钟为基准，控制采样点播放的数量
// 如果 sync_type 是视频或外部主时钟，则返回所需的样本数以获得更好的同步
static int synchronize_audio(VideoState *is, int nb_samples)
{
int wanted_nb_samples = nb_samples;
// 如果不是主时钟，那么我们会尝试删除或添加样本来纠正时钟
if (get_master_sync_type(is) != AV_SYNC_AUDIO_MASTER) {
double diff, avg_diff;
int min_nb_samples, max_nb_samples;
diff = get_clock(&is->audclk) - get_master_clock(is);
if (!isnan(diff) && fabs(diff) < AV_NOSYNC_THRESHOLD) {
is->audio_diff_cum = diff + is->audio_diff_avg_coef * is->audio_diff_cum;
if (is->audio_diff_avg_count < AUDIO_DIFF_AVG_NB) {
/* not enough measures to have a correct estimate */
is->audio_diff_avg_count++;
} else {
/* estimate the A-V difference */
avg_diff = is->audio_diff_cum * (1.0 - is->audio_diff_avg_coef);
if (fabs(avg_diff) >= is->audio_diff_threshold) {
wanted_nb_samples = nb_samples + (int)(diff * is->audio_src.freq);
min_nb_samples = ((nb_samples * (100 - SAMPLE_CORRECTION_PERCENT_MAX) / 100));
max_nb_samples = ((nb_samples * (100 + SAMPLE_CORRECTION_PERCENT_MAX) / 100));
wanted_nb_samples = av_clip(wanted_nb_samples, min_nb_samples, max_nb_samples);
}
av_log(NULL, AV_LOG_TRACE, "diff=%f adiff=%f sample_diff=%d apts=%0.3f %f\n", diff, avg_diff, wanted_nb_samples - nb_samples, is->audio_clock, is->audio_diff_threshold);
}
} else {
/* too big difference : may be initial PTS errors, so reset A-V filter */
is->audio_diff_avg_count = 0;
is->audio_diff_cum = 0;
}
}
return wanted_nb_samples;
}3、以音频或者外部时钟为基准，计算remaining_time
static void refresh_loop_wait_event(VideoState *is, SDL_Event *event)
{
double remaining_time = 0.0;
SDL_PumpEvents();
while (!SDL_PeepEvents(event, 1, SDL_GETEVENT, SDL_FIRSTEVENT, SDL_LASTEVENT)) {
if (!cursor_hidden && av_gettime_relative() - cursor_last_shown > CURSOR_HIDE_DELAY) {
SDL_ShowCursor(0);
cursor_hidden = 1;
}
if (remaining_time > 0.0)
av_usleep((int64_t)(remaining_time * 1000000.0));
remaining_time = REFRESH_RATE;
if (is->show_mode != SHOW_MODE_NONE && (!is->paused || is->force_refresh))
video_refresh(is, &remaining_time);
SDL_PumpEvents();
}
}
/* called to display each frame */
static void video_refresh(void *opaque, double *remaining_time)
{
VideoState *is = opaque;
double time;
Frame *sp, *sp2;
if (!is->paused && get_master_sync_type(is) == AV_SYNC_EXTERNAL_CLOCK && is->realtime)
check_external_clock_speed(is);
if (!display_disable && is->show_mode != SHOW_MODE_VIDEO && is->audio_st) {
time = av_gettime_relative() / 1000000.0;
if (is->force_refresh || is->last_vis_time + rdftspeed < time) {
video_display(is);
is->last_vis_time = time;
}
*remaining_time = FFMIN(*remaining_time, is->last_vis_time + rdftspeed - time);
}
if (is->video_st) {
retry:
if (frame_queue_nb_remaining(&is->pictq) == 0) {
// nothing to do, no picture to display in the queue
} else {
double last_duration, duration, delay;
Frame *vp, *lastvp;
/* dequeue the picture */
lastvp = frame_queue_peek_last(&is->pictq);
vp = frame_queue_peek(&is->pictq);
if (vp->serial != is->videoq.serial) {
frame_queue_next(&is->pictq);
goto retry;
}
if (lastvp->serial != vp->serial)
is->frame_timer = av_gettime_relative() / 1000000.0;
if (is->paused)
goto display;
/* compute nominal last_duration */
last_duration = vp_duration(is, lastvp, vp);
delay = compute_target_delay(last_duration, is);
time= av_gettime_relative()/1000000.0;
if (time < is->frame_timer + delay) {
*remaining_time = FFMIN(is->frame_timer + delay - time, *remaining_time);
goto display;
}
is->frame_timer += delay;
if (delay > 0 && time - is->frame_timer > AV_SYNC_THRESHOLD_MAX)
is->frame_timer = time;
SDL_LockMutex(is->pictq.mutex);
if (!isnan(vp->pts))
update_video_pts(is, vp->pts, vp->serial);
SDL_UnlockMutex(is->pictq.mutex);
if (frame_queue_nb_remaining(&is->pictq) > 1) {
Frame *nextvp = frame_queue_peek_next(&is->pictq);
duration = vp_duration(is, vp, nextvp);
if(!is->step && (framedrop>0 || (framedrop && get_master_sync_type(is) != AV_SYNC_VIDEO_MASTER)) && time > is->frame_timer + duration){
is->frame_drops_late++;
frame_queue_next(&is->pictq);
goto retry;
}
}
if (is->subtitle_st) {
while (frame_queue_nb_remaining(&is->subpq) > 0) {
sp = frame_queue_peek(&is->subpq);
if (frame_queue_nb_remaining(&is->subpq) > 1)
sp2 = frame_queue_peek_next(&is->subpq);
else
sp2 = NULL;
if (sp->serial != is->subtitleq.serial
|| (is->vidclk.pts > (sp->pts + ((float) sp->sub.end_display_time / 1000)))
|| (sp2 && is->vidclk.pts > (sp2->pts + ((float) sp2->sub.start_display_time / 1000))))
{
if (sp->uploaded) {
int i;
for (i = 0; i < sp->sub.num_rects; i++) {
AVSubtitleRect *sub_rect = sp->sub.rects[i];
uint8_t *pixels;
int pitch, j;
if (!SDL_LockTexture(is->sub_texture, (SDL_Rect *)sub_rect, (void **)&pixels, &pitch)) {
for (j = 0; j < sub_rect->h; j++, pixels += pitch)
memset(pixels, 0, sub_rect->w << 2);
SDL_UnlockTexture(is->sub_texture);
}
}
}
frame_queue_next(&is->subpq);
} else {
break;
}
}
}
frame_queue_next(&is->pictq);
is->force_refresh = 1;
if (is->step && !is->paused)
stream_toggle_pause(is);
}
display:
/* display picture */
if (!display_disable && is->force_refresh && is->show_mode == SHOW_MODE_VIDEO && is->pictq.rindex_shown)
video_display(is);
}
is->force_refresh = 0;
if (show_status) {
AVBPrint buf;
static int64_t last_time;
int64_t cur_time;
int aqsize, vqsize, sqsize;
double av_diff;
cur_time = av_gettime_relative();
if (!last_time || (cur_time - last_time) >= 30000) {
aqsize = 0;
vqsize = 0;
sqsize = 0;
if (is->audio_st)
aqsize = is->audioq.size;
if (is->video_st)
vqsize = is->videoq.size;
if (is->subtitle_st)
sqsize = is->subtitleq.size;
av_diff = 0;
if (is->audio_st && is->video_st)
av_diff = get_clock(&is->audclk) - get_clock(&is->vidclk);
else if (is->video_st)
av_diff = get_master_clock(is) - get_clock(&is->vidclk);
else if (is->audio_st)
av_diff = get_master_clock(is) - get_clock(&is->audclk);
av_bprint_init(&buf, 0, AV_BPRINT_SIZE_AUTOMATIC);
av_bprintf(&buf,
"%7.2f %s:%7.3f fd=%4d aq=%5dKB vq=%5dKB sq=%5dB f=%"PRId64"/%"PRId64" \r",
get_master_clock(is),
(is->audio_st && is->video_st) ? "A-V" : (is->video_st ? "M-V" : (is->audio_st ? "M-A" : " ")),
av_diff,
is->frame_drops_early + is->frame_drops_late,
aqsize / 1024,
vqsize / 1024,
sqsize,
is->video_st ? is->viddec.avctx->pts_correction_num_faulty_dts : 0,
is->video_st ? is->viddec.avctx->pts_correction_num_faulty_pts : 0);
if (show_status == 1 && AV_LOG_INFO > av_log_get_level())
fprintf(stderr, "%s", buf.str);
else
av_log(NULL, AV_LOG_INFO, "%s", buf.str);
fflush(stderr);
av_bprint_finalize(&buf, NULL);
last_time = cur_time;
}
}
}