obs-studio 数据采集 渲染 编码过程

程序启动时 会调用 obs_init_video函数，创建一个obs_video_thread 线程

static int obs_init_video(struct obs_video_info *ovi)
{
	struct obs_core_video *video = &obs->video;
	struct video_output_info vi;
	int errorcode;

	make_video_info(&vi, ovi);
	video->base_width     = ovi->base_width;
	video->base_height    = ovi->base_height;
	video->output_width   = ovi->output_width;
	video->output_height  = ovi->output_height;
	video->gpu_conversion = ovi->gpu_conversion;
	video->scale_type     = ovi->scale_type;

	set_video_matrix(video, ovi);

	errorcode = video_output_open(&video->video, &vi);

	if (errorcode != VIDEO_OUTPUT_SUCCESS) {
		if (errorcode == VIDEO_OUTPUT_INVALIDPARAM) {
			blog(LOG_ERROR, "Invalid video parameters specified");
			return OBS_VIDEO_INVALID_PARAM;
		} else {
			blog(LOG_ERROR, "Could not open video output");
		}
		return OBS_VIDEO_FAIL;
	}

	gs_enter_context(video->graphics);

	if (ovi->gp