Pyramid Lattice Vector Quantization For Coding Motion Vector Differences

A method comprising:

• generating reconstructed block data by decoding a current block from a current frame from an encoded bitstream, wherein decoding the current block includes obtaining a motion vector for decoding the current block by:
• obtaining a shell index by decoding the shell index from the encoded bitstream;
• in response to a determination that the shell index is zero, using a zero motion vector as a motion vector difference;
• and
• in response to a determination that the shell index is greater than zero:
• obtaining a quadrant value by decoding the quadrant value from the encoded bitstream;
• in response to a determination that the shell index is less than or equal to one, identifying a distance value of zero;
• in response to a determination that the shell index is greater than one, identifying the distance value by decoding the distance value from the encoded bitstream;
• in response to a determination that the quadrant value is zero:
• identify the distance value as a vertical component of the motion vector difference;
• and
• identifying a result of subtracting the distance value from the shell index as a horizontal component of the motion vector difference;
• in response to a determination that the quadrant value is one:
• identify, as the vertical component of the motion vector difference, a sum of one and the distance value;
• and
• identifying, as the horizontal component of the motion vector difference, a sum of one, the distance value, and an additive inverse of the shell index;
• in response to a determination that the quadrant value is two:
• identify, as the vertical component of the motion vector difference, an additive inverse of the distance value;
• and
• identifying, as the horizontal component of the motion vector difference, a sum of the distance value, and an additive inverse of the shell index;
• and
• in response to a determination that the quadrant value is three:
• identify, as the vertical component of the motion vector difference, a result of subtracting one from an additive inverse of the distance value;
• and
• identifying, as the horizontal component of the motion vector difference, a result of subtracting one from a result of subtracting the distance value from the shell index;
• and
• obtaining, as the motion vector, a sum of the motion vector difference and a predicted motion vector;
• including the reconstructed block data in a reconstructed frame;
• and
• outputting the reconstructed frame.