opus裸流写文件

	 if (fdAudioOut == NULL) {
	     // fdAudioOut = fopen("/mnt/sdcard/send.opus", "wb");
	 }
	 if (fdAudioOut != NULL) {
	     uint32_t magicOpus = 0x20200820;
	     fwrite(&magicOpus, 1, 4, fdAudioOut);
	     fwrite(&frame_head->length, 1, 4, fdAudioOut);
	     fwrite(frame_data, 1, frame_head->length, fdAudioOut);
	 }

写完就可以使用vlc播放啦