translation.en: The tricky part is that those signals, those changes that we're after, are extremely subtle, so we have to be very careful when you try to separate them from noise that always exists in videos.
translation.zh: 棘手的部分是，那些信号， 那些我们要放大的信号十分微小， 所以我们必须把它们和视频中存在的噪音 区分出来。