Whenever I render a video it comes out playing at 3x speed. So originally a 20 second video comes out like 4 seconds long. I used mograph text with polyfx and animated it, with a video playing in the background. I'm an editing noob so I might have a setting wrong somewhere?
Bare it in mind that when you play the animation in the Cinema 4D window it will appear at the right speed. AS you computer is processing the animation whilst showing it's unrendered self. when your rendering it process the information before it is played so the video will be smoother so that initial slowness wont be presence as the processing of the images will be a lot less due to them already being processed.
Basically it forms an illusion whilst being played in the Cinema 4D window. Rendering is the truest form of the animation.