h.264, which is the protocol most cameras record to, isn't even synchronous. There's no mandated field length within the codec. Which means for those of us who record audio, h.264 will drift by at least a frame after less than 5 minutes of recording. More than ten minutes and you can be off by three frames or more. After that it's all kinda wooly; the video recording is dumping data where it fits and speeding up or slowing down to make the audio work. Meanwhile it's spitting out a secondary path for monitoring which Windows is playing with asynchronously as well. Linux is no better. Unless you've got a dedicated hard-coded time-synched recorder it's all spitting shit every which way and it'll drop frames, lock up, whatever. If you're using a webcam it doesn't much matter because we accept that webcams are going to be shit. But if you're recording, you're in for a bad time.