obs lib屏幕捕捉相关流程整理

切入点：

video_thread线程主循环，只要video->stop为false，会循环调用video_output_cur_frame来捕捉当前屏幕。

//碧麟标注裁剪版本
static void *video_thread(void *param)
{
	struct video_output *video = param;
    
    //设置线程名字
	os_set_thread_name("video-io: video thread");

	//线程主循环
	while (os_sem_wait(video->update_semaphore) == 0) {
		if (video->stop)
			break;

        //循环调用video_output_cur_frame获取当前屏幕
		while (!video->stop && !video_output_cur_frame(video)) {
			os_atomic_inc_long(&video->total_frames);
		}

	}

	return NULL;
}

这里用到video_output核心结构体 ，结构体定义如下

捕捉当前帧核心逻辑

//捕捉当前帧
static inline bool video_output_cur_frame(struct video_output *video)
{
    //帧信息
	struct cached_frame_info *frame_info;
	bool complete;
	bool skipped;

	/* -------------------------------- */

	pthread_mutex_lock(&video->data_mutex);

	frame_info = &video->cache[video->first_added];

	pthread_mutex_unlock(&video->data_mutex);

	/* -------------------------------- */

	pthread_mutex_lock(&video->input_mutex);

	for (size_t i = 0; i < video->inputs.num; i++) {
		struct video_input *input = video->inputs.array + i;
		struct video_data frame = frame_info->frame;

		if (scale_video_output(input, &frame))
			input->callback(input->param, &frame);
	}

	pthread_mutex_unlock(&video->input_mutex);

	/* -------------------------------- */

	pthread_mutex_lock(&video->data_mutex);

	frame_info->frame.timestamp += video->frame_time;
	complete = --frame_info->count == 0;
	skipped = frame_info->skipped > 0;

	if (complete) {
		if (++video->first_added == video->info.cache_size)
			video->first_added = 0;

		if (++video->available_frames == video->info.cache_size)
			video->last_added = video->first_added;
	} else if (skipped) {
		--frame_info->skipped;
		os_atomic_inc_long(&video->skipped_frames);
	}

	pthread_mutex_unlock(&video->data_mutex);

	/* -------------------------------- */

	return complete;
}