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初始化
/* Called from the main */ int main(int argc, char **argv) { int flags; VideoState *is; // av_log_set_level(AV_LOG_TRACE); init_dynload(); // 1. 对FFmpeg的初始化 av_log_set_flags(AV_LOG_SKIP_REPEATED); parse_loglevel(argc, argv, options); /// av_log_set_level(AV_LOG_DEBUG); /* register all codecs, demux and protocols */ #if CONFIG_AVDEVICE avdevice_register_all(); #endif avformat_network_init(); init_opts(); signal(SIGINT , sigterm_handler); /* Interrupt (ANSI). */ signal(SIGTERM, sigterm_handler); /* Termination (ANSI). */ show_banner(argc, argv, options); // 2. 对传递的参数进行初始化 parse_options(NULL, argc, argv, options, opt_input_file); if (!input_filename) { show_usage(); av_log(NULL, AV_LOG_FATAL, "An input file must be specified "); av_log(NULL, AV_LOG_FATAL, "Use -h to get full help or, even better, run 'man %s' ", program_name); exit(1); } /* 是否显示视频 */ if (display_disable) { video_disable = 1; } // 3. SDL的初始化 flags = SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER; /* 是否运行音频 */ if (audio_disable) flags &= ~SDL_INIT_AUDIO; else { /* Try to work around an occasional ALSA buffer underflow issue when the * period size is NPOT due to ALSA resampling by forcing the buffer size. */ if (!SDL_getenv("SDL_AUDIO_ALSA_SET_BUFFER_SIZE")) SDL_setenv("SDL_AUDIO_ALSA_SET_BUFFER_SIZE","1", 1); } if (display_disable) flags &= ~SDL_INIT_VIDEO; if (SDL_Init (flags)) { av_log(NULL, AV_LOG_FATAL, "Could not initialize SDL - %s ", SDL_GetError()); av_log(NULL, AV_LOG_FATAL, "(Did you set the DISPLAY variable?) "); exit(1); } SDL_EventState(SDL_SYSWMEVENT, SDL_IGNORE); SDL_EventState(SDL_USEREVENT, SDL_IGNORE); av_init_packet(&flush_pkt); // 初始化flush_packet flush_pkt.data = (uint8_t *)&flush_pkt; // 初始化为数据指向自己本身 // 4. 创建窗口 if (!display_disable) { int flags = SDL_WINDOW_HIDDEN; if (alwaysontop) #if SDL_VERSION_ATLEAST(2,0,5) flags |= SDL_WINDOW_ALWAYS_ON_TOP; #else av_log(NULL, AV_LOG_WARNING, "Your SDL version doesn't support SDL_WINDOW_ALWAYS_ON_TOP. Feature will be inactive. "); #endif if (borderless) flags |= SDL_WINDOW_BORDERLESS; else flags |= SDL_WINDOW_RESIZABLE; window = SDL_CreateWindow(program_name, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, default_width, default_height, flags); SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "linear"); if (window) { // 创建renderer renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC); if (!renderer) { av_log(NULL, AV_LOG_WARNING, "Failed to initialize a hardware accelerated renderer: %s ", SDL_GetError()); renderer = SDL_CreateRenderer(window, -1, 0); } if (renderer) { if (!SDL_GetRendererInfo(renderer, &renderer_info)) av_log(NULL, AV_LOG_VERBOSE, "Initialized %s renderer. ", renderer_info.name); } } if (!window || !renderer || !renderer_info.num_texture_formats) { av_log(NULL, AV_LOG_FATAL, "Failed to create window or renderer: %s", SDL_GetError()); do_exit(NULL); } } // 5. 通过stream_open函数，开启read_thread读取线程 is = stream_open(input_filename, file_iformat); if (!is) { av_log(NULL, AV_LOG_FATAL, "Failed to initialize VideoState! "); do_exit(NULL); } // 6. 事件响应 event_loop(is); /* never returns */ return 0; }
初始化主要在main里面，主要做了如下几件事：
1. SDL_Init，主要是SDL_INIT_VIDEO的⽀持
2. SDL_CreateWindow，创建主窗⼝
3. SDL_CreateRender，基于主窗⼝创建renderer，⽤于渲染输出。
4. stream_open
5. event_loop，播放控制事件响应循环，但也负责了video显示输出。
video_refresh()
/* called to display each frame */ /* 非暂停或强制刷新的时候，循环调用video_refresh */ 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) {// 帧队列是否为空 // nothing to do, no picture to display in the queue // 什么都不做，队列中没有图像可显示 } else { // 重点是音视频同步 double last_duration, duration, delay; Frame *vp, *lastvp; /* dequeue the picture */ // 从队列取出上一个Frame lastvp = frame_queue_peek_last(&is->pictq);//读取上一帧 vp = frame_queue_peek(&is->pictq); // 读取待显示帧 // lastvp 上一帧(正在显示的帧) // vp 等待显示的帧 if (vp->serial != is->videoq.serial) { // 如果不是最新的播放序列，则将其出队列，以尽快读取最新序列的帧 frame_queue_next(&is->pictq); goto retry; } if (lastvp->serial != vp->serial) { // 新的播放序列重置当前时间 is->frame_timer = av_gettime_relative() / 1000000.0; } if (is->paused) { goto display; printf("视频暂停is->paused"); } /* compute nominal last_duration */ //lastvp上一帧，vp当前帧 ，nextvp下一帧 //last_duration 计算上一帧应显示的时长 last_duration = vp_duration(is, lastvp, vp); // 经过compute_target_delay方法，计算出待显示帧vp需要等待的时间 // 如果以video同步，则delay直接等于last_duration。 // 如果以audio或外部时钟同步，则需要比对主时钟调整待显示帧vp要等待的时间。 delay = compute_target_delay(last_duration, is); time= av_gettime_relative()/1000000.0; // is->frame_timer 实际上就是上一帧lastvp的播放时间, // is->frame_timer + delay 是待显示帧vp该播放的时间 if (time < is->frame_timer + delay) { //判断是否继续显示上一帧 // 当前系统时刻还未到达上一帧的结束时刻，那么还应该继续显示上一帧。 // 计算出最小等待时间 *remaining_time = FFMIN(is->frame_timer + delay - time, *remaining_time); goto display; } // 走到这一步，说明已经到了或过了该显示的时间，待显示帧vp的状态变更为当前要显示的帧 is->frame_timer += delay; // 更新当前帧播放的时间 if (delay > 0 && time - is->frame_timer > AV_SYNC_THRESHOLD_MAX) { is->frame_timer = time; //如果和系统时间差距太大，就纠正为系统时间 } SDL_LockMutex(is->pictq.mutex); if (!isnan(vp->pts)) update_video_pts(is, vp->pts, vp->pos, vp->serial); // 更新video时钟 SDL_UnlockMutex(is->pictq.mutex); //丢帧逻辑 if (frame_queue_nb_remaining(&is->pictq) > 1) {//有nextvp才会检测是否该丢帧 Frame *nextvp = frame_queue_peek_next(&is->pictq); duration = vp_duration(is, vp, nextvp); if(!is->step // 非逐帧模式才检测是否需要丢帧 is->step==1 为逐帧播放 && (framedrop>0 || // cpu解帧过慢 (framedrop && get_master_sync_type(is) != AV_SYNC_VIDEO_MASTER)) // 非视频同步方式 && time > is->frame_timer + duration // 确实落后了一帧数据 ) { printf("%s(%d) dif:%lfs, drop frame ", __FUNCTION__, __LINE__, (is->frame_timer + duration) - time); is->frame_drops_late++; // 统计丢帧情况 frame_queue_next(&is->pictq); // 这里实现真正的丢帧 //(这里不能直接while丢帧，因为很可能audio clock重新对时了，这样delay值需要重新计算) goto retry; //回到函数开始位置，继续重试 } } 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); // 当前vp帧出队列 is->force_refresh = 1; /* 说明需要刷新视频帧 */ 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); // 重点是显示 } 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" ", 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; } } }
video_image_display()
static void video_image_display(VideoState *is) { Frame *vp; Frame *sp = NULL; SDL_Rect rect; // keep_last的作用就出来了,我们是有调用frame_queue_next, 但最近出队列的帧并没有真正销毁 // 所以这里可以读取出来显示 vp = frame_queue_peek_last(&is->pictq); if (is->subtitle_st) { if (frame_queue_nb_remaining(&is->subpq) > 0) { sp = frame_queue_peek(&is->subpq); if (vp->pts >= sp->pts + ((float) sp->sub.start_display_time / 1000)) { if (!sp->uploaded) { uint8_t* pixels[4]; int pitch[4]; int i; if (!sp->width || !sp->height) { sp->width = vp->width; sp->height = vp->height; } if (realloc_texture(&is->sub_texture, SDL_PIXELFORMAT_ARGB8888, sp->width, sp->height, SDL_BLENDMODE_BLEND, 1) < 0) return; for (i = 0; i < sp->sub.num_rects; i++) { AVSubtitleRect *sub_rect = sp->sub.rects[i]; sub_rect->x = av_clip(sub_rect->x, 0, sp->width ); sub_rect->y = av_clip(sub_rect->y, 0, sp->height); sub_rect->w = av_clip(sub_rect->w, 0, sp->width - sub_rect->x); sub_rect->h = av_clip(sub_rect->h, 0, sp->height - sub_rect->y); is->sub_convert_ctx = sws_getCachedContext(is->sub_convert_ctx, sub_rect->w, sub_rect->h, AV_PIX_FMT_PAL8, sub_rect->w, sub_rect->h, AV_PIX_FMT_BGRA, 0, NULL, NULL, NULL); if (!is->sub_convert_ctx) { av_log(NULL, AV_LOG_FATAL, "Cannot initialize the conversion context "); return; } if (!SDL_LockTexture(is->sub_texture, (SDL_Rect *)sub_rect, (void **)pixels, pitch)) { sws_scale(is->sub_convert_ctx, (const uint8_t * const *)sub_rect->data, sub_rect->linesize, 0, sub_rect->h, pixels, pitch); SDL_UnlockTexture(is->sub_texture); } } sp->uploaded = 1; } } else sp = NULL; } } //将帧宽高按照sar最大适配到窗口，并通过rect返回视频帧在窗口的显示位置和宽高 calculate_display_rect(&rect, is->xleft, is->ytop, is->width, is->height, vp->width, vp->height, vp->sar); // rect.x = rect.w /2; // 测试 // rect.w = rect.w /2; // 缩放实际不是用sws， 缩放是sdl去做的 if (!vp->uploaded) { // 把yuv数据更新到vid_texture if (upload_texture(&is->vid_texture, vp->frame, &is->img_convert_ctx) < 0) return; vp->uploaded = 1; vp->flip_v = vp->frame->linesize[0] < 0; } set_sdl_yuv_conversion_mode(vp->frame); SDL_RenderCopyEx(renderer, is->vid_texture, NULL, &rect, 0, NULL, vp->flip_v ? SDL_FLIP_VERTICAL : 0); set_sdl_yuv_conversion_mode(NULL); if (sp) { #if USE_ONEPASS_SUBTITLE_RENDER SDL_RenderCopy(renderer, is->sub_texture, NULL, &rect); #else int i; double xratio = (double)rect.w / (double)sp->width; double yratio = (double)rect.h / (double)sp->height; for (i = 0; i < sp->sub.num_rects; i++) { SDL_Rect *sub_rect = (SDL_Rect*)sp->sub.rects[i]; SDL_Rect target = {.x = rect.x + sub_rect->x * xratio, .y = rect.y + sub_rect->y * yratio, .w = sub_rect->w * xratio, .h = sub_rect->h * yratio}; SDL_RenderCopy(renderer, is->sub_texture, sub_rect, &target); } #endif } }