If you use an MP4 on an image plane, it may drastically slow down your viewport. If it does, switch the image plane's display mode to None when you aren't actively using it as a reference. codec issues - Forums, Autodesk
If you need to import an MP4 into Maya to use as a background for tracing movements: Maya.mp4
MP4 files use temporal compression, which makes "scrubbing" (dragging) through the timeline laggy or inaccurate as Maya tries to calculate compressed frames. If you use an MP4 on an image
In Maya, create an and check the box for Use Image Sequence . In Maya, create an and check the box for Use Image Sequence
Some third-party plugins can force real-time MP4 playback on image planes by using custom FFmpeg builds . Exporting MP4 via Playblast
Use the Maya Hardware 2.0 renderer to output a sequence of frames, then compile them into an MP4 using video editing software. Quick Tips for Maya Video Workflow
A "Playblast" is a way to preview your animation without a full render.