Actually, audio data (AC3, DTS, LPCM, etc.) and video data (MPEG-2, MPEG-4, etc.) are embedded in a container (.ts, .ps, .m2ts, .vob, .avi, .mkv, etc.). There is no such thing as a video file. It is the case that you'll rarely find a container with video streams that does not also have audio streams - since silent video is unusual - but containers with audio only is very common, especially in the case of encoded multi-channel audio. Its conceivable that there would be different engines that handle unencoded audio data - like LPCM - and encoded audio data - like AC3 - but the fact that stream handling is split between engines and one is called audio and the other video is an architecture that is not intuitively obvious.