Sigmondo can generally play all video formats and sizes that your Apple TV can play. You can look up your Apple TV on the Apple Support page to find the exact specifications.
Apple TV connected to HD display
Video and image dimensions
For the Media Media Area, you can use 1920×1080 px or 1280×720 px to fit the frame. This is the size of Full-HD or HD in video.
For any other image sizes you have an option to scale to fit or to scale to fill (Note: this is only available for images not videos).
Video file formats
Here, for example, are the specifications for the Apple TV 4: Use mp4 or mov with H.264 for best results in video quality and size.
H.264 video up to 1080p, up to 60 frames per second, High or Main Profile level 4.2 or lower.
Find more details on apple.com.
Logo file format
For the Logo Area you can use PNG with transparency. The maximum space for logo is 340×180 px.
Apple TV connected to 4K display
You can use up to 2x the pixel size as above. And use newer formats like AVC/HEVC (Main/Main 10 profile) up to 2160p, 60 fps for videos.