代碼堆棧回溯
ffplayd.exe!video_image_display(VideoState * is) 行 1036 C
ffplayd.exe!video_display(VideoState * is) 行 1371 C
ffplayd.exe!video_refresh(void * opaque, double * remaining_time) 行 1690 C
ffplayd.exe!refresh_loop_wait_event(VideoState * is, SDL_Event * event) 行 3229 C
ffplayd.exe!event_loop(VideoState * cur_stream) 行 3269 C
ffplayd.exe!main(int argc, char * * argv) 行 3768 C
調用 SDL_RenderCopyEx(renderer, is->vid_texture, NULL, &rect, 0, NULL, vp->flip_v ? SDL_FLIP_VERTICAL : 0)實作界面的渲染
渲染的時機非常重要
1）refresh_loop_wait_event函數剖析
static void refresh_loop_wait_event(VideoState *is, SDL_Event *event) {
double remaining_time = 0.0;
//調用該函數搜集輸入裝置的事件（例如鍵盤輸入，滑鼠移動），然後存放在事件隊列中，等待SDL_PeepEvents擷取事件
SDL_PumpEvents();
//SDL_GETEVENT操作指定的SDL_PeepEvents會讀取事件隊列中的事件消息，并且是将讀取的事件移除出隊列
//while循環!說明了隻要事件隊列有消息，優先執行隊列中的事件，然後才進行視訊的渲染
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);
//重新搜尋輸入裝置的事件，如果屏蔽掉該函數的調用，将會導緻鍵盤的輸入無法進行事件隊列，導緻鍵盤輸入無效，例如嘗試按下q停止視訊播放
SDL_PumpEvents();
}
}
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);
//如果不是音頻資料，也就是字幕或者聲音顯示或者播放
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);
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->pos, 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)
is->force_refresh = 0;
if (show_status) {
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_log(NULL, AV_LOG_INFO,
"%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);
fflush(stdout);
last_time = cur_time;
static void frame_queue_next(FrameQueue *f)
if (f->keep_last && !f->rindex_shown) {
f->rindex_shown = 1;
return;
//釋放已經顯示過的幀
frame_queue_unref_item(&f->queue[f->rindex]);
//++f->rindex 表示目前幀已經顯示完成，f->rindex指向下一個等待顯示的幀
if (++f->rindex == f->max_size)
f->rindex = 0;
SDL_LockMutex(f->mutex);
//等待顯示的幀數減一
f->size--;
SDL_CondSignal(f->cond);
SDL_UnlockMutex(f->mutex);
/* return the number of undisplayed frames in the queue */
static int frame_queue_nb_remaining(FrameQueue *f)
//f->size是目前隊列中的幀數， f->rindex_shown是已經顯示過的幀數
return f->size - f->rindex_shown;
/* return last shown position */
static int64_t frame_queue_last_pos(FrameQueue *f)
//說明rindex是上一個顯示的幀，rindex+1就是等待顯示的幀
Frame *fp = &f->queue[f->rindex];
if (f->rindex_shown && fp->serial == f->pktq->serial)
return fp->pos;
else
return -1;
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