Video decoder for determining a motion vector from a scaled vector and a difference vector

A video decoding apparatus comprising:

• memory means for storing at least first and second reference pictures;
• decoding means for decoding a transmitted first motion vector and a transmitted motion vector difference, and for further decoding a second motion vector corresponding to a motion vector obtained by adding a scaled motion vector and the motion vector difference, said scaled motion vector being derived by scaling the first motion vector to a motion vector for the second reference picture;
• prediction signal forming means for forming a prediction signal, using a first reference signal designated by the first motion vector for the first reference picture and a second reference signal designated by the second motion vector for the second reference picture read out of said memory means;
• and
• decoding means for decoding a transmitted difference signal and for obtaining an output signal by adding the difference signal and said prediction signal.

A method of decoding a video signal comprising the steps of:

• storing at least first and second reference pictures in a memory;
• decoding a transmitted first motion vector and a transmitted motion vector difference, and for further decoding a second motion vector by adding a scaled motion vector and the motion vector difference, said scaled motion vector being derived by scaling the first motion vector to a motion vector for the second reference picture;
• forming a prediction signal, using a first reference signal designated by the first motion vector for the first reference picture and a second reference signal designated by the second motion vector for the second reference picture read out of said memory means;
• and
• decoding a transmitted difference signal and obtaining an output signal by adding the difference signal and the prediction signal.

A method of decoding a video signal comprising the steps of:

• storing at least first and second reference pictures in a memory;
• decoding a transmitted first motion vector and a transmitted motion vector difference and for further decoding a second motion vector corresponding to a motion vector obtained by adding a scaled motion vector and the motion vector difference, said scaled motion vector being derived by scaling the first motion vector to a motion vector for the second reference picture;
• forming a prediction signal, using a first reference signal designated by the first motion vector for the first reference picture and a second reference signal designated by the second motion vector for the second reference picture read out of said memory means;
• and
• decoding a transmitted difference signal and obtaining an output signal by adding the difference signal and the prediction signal.