Some devices (like older Apple TVs) may require the NAS to transcode MP4 files if the audio codec (like 6-channel AC3) isn't supported.

The query typically refers to one of two things: the technical process of playing video files on a Nintendo DS or using the Synology DS Video app to stream MP4s from a NAS.

Were you looking for a guide on how to for videos, or are you troubleshooting a Synology NAS setup?