A multimedia processor includes an audio processor configured to process an audio input signal to generate an audio output signal and an assistant signal, and a video processor coupled with the audio processor and configured to process video input signal and the assistant signal to generate a video output signal simultaneously according to the video input signal and the assistant signal. Provided with the assistant signal, the video processor acquires more video processing-related information for rendering video content in a more realistic manner. Mal-motion detection can thus be prevented, and video quality can be improved.