学步园

static int decode_thread(void *arg)
{
	/*(1)：首先调用av_open_input_file()直接识别文件格式和间接识别媒体格式(媒体格式
	是通过av_open_input_file调用av_open_input_stream 再调用ic->iformat->read_header(ic, ap)
	来识别的，所以是间接识别媒体格式)。*/
	err = av_open_input_file(&ic, is->filename, is->iformat, 0, ap);

	err = av_find_stream_info(ic);

	/* open the streams (2)：接着调用stream_component_open()查找打开编解码器codec 
	并启动音频和视频解码线程。*/
	for(i = 0; i < ic->nb_streams; i++) 
	{
		stream_component_open(is, i);
	}

	for(;;) 
	{
		/*(3)：再接着解析文件，分离音视频数据包，排序进入队列。*/        
		ret = av_read_frame(ic, pkt);

		//将Packet放入对应的队列:audio, video , subtitle
		if (pkt->stream_index == is->audio_stream) {
			packet_queue_put(&is->audioq, pkt);
		} else if (pkt->stream_index == is->video_stream) {
			packet_queue_put(&is->videoq, pkt);
		} else if (pkt->stream_index == is->subtitle_stream) {
			packet_queue_put(&is->subtitleq, pkt);
		} 
		else {
			av_free_packet(pkt);
		}
	}

	/* wait until the end */
	while (!is->abort_request) {
		SDL_Delay(100);
	}

	/* close each stream */
	for(i = 0; i < ic->nb_streams; i++) 
	{
		stream_component_close(is, i);
	}

	av_close_input_file(is->ic);

	return 0;
}