It does not read video files directly. R4 carts are designed for game ROMs, not video playback.
However, there are some ways to play video on a DS with an R4:
* DS-specific video players: There are some DS applications available that can play video files from your SD card. These apps usually support specific formats like AVI or MP4, but may have limited features.
* DS homebrew: Some DS homebrew applications allow you to play video files, but these are not official applications and may require some technical knowledge to install.
If you want to play video on a DS, the most straightforward option is to use a dedicated video player specifically designed for the system.