Variable length decoding of motion vectors

A motion vector decoding apparatus for converting a variable length coded representation of a motion vector into an original vector using a difference component of the motion vector, comprising:

• X-axis motion vector component decoding means for decoding an X-axis component of the motion vector in response to first and second X-axis motion vector difference components;
• and
• Y-axis motion vector component decoding means for decoding a Y-axis component of the motion vector in response to first and second Y-axis motion vector difference components, said Y-axis motion vector component decoding means includes:
• a first buffer for storing temporarily the first Y-axis motion vector difference component in response to a first control signal;
• a second buffer for storing temporarily the second Y-axis motion vector difference component in response to the first control signal;
• a first adder for adding an output signal from said first buffer and the Y-axis motion vector component;
• a third buffer for storing temporarily an output signal from said first adder in response to a second control signal;
• a second adder for adding an output signal from said second buffer and the Y-axis motion vector component;
• a fourth buffer for storing temporarily an output signal from said second adder in response to the second control signal;
• a comparator for comparing absolute values of output signals from said third and fourth buffers with each other and outputting an absolute Y-axis motion vector component in accordance with the compared result, the absolute Y-axis motion vector component having a value within the range from -8 to 7;
• a selector for selecting one of the output signals from said third and fourth buffers in response to an output signal from said comparator;
• a fifth buffer responsive to third and fourth control signals for storing temporarily an output signal from said selector and outputting the stored signal as the Y-axis motion vector component to said first and second adders;
• and
• a controller for generating the first to fourth control signals and a Y-axis valid signal in response to a clock signal and a Y-axis difference valid signal and outputting the generated first to fourth control signals to said first to fifth buffers, said controller outputting the Y-axis valid signal externally synchronously with the output of the Y-axis motion vector component from said fifth buffer.

A motion vector decoding method for converting a variable length coded representation of a motion vector into an original vector using a difference component of the motion vector, comprising the steps of:

• (a) decoding an X-axis component of the motion vector in response to first and second X-axis motion vector difference components, decoding the X-axis motion vector component includes the steps of:
• (a-1) checking whether an X-axis difference valid signal has been inputted, to check whether the first and second X-axis motion vector difference components have been inputted, the first and second X-axis motion vector difference components being (N+1)th X-axis motion vector components;
• (a-2) checking whether a first buffer is in a clear state, if it is checked at said step (a-1) that the X-axis difference valid signal has been inputted;
• (a-3) setting an output of said first buffer to 0 if it is checked at said step (a-2) that said first buffer is in the clear state and allowing said first buffer to output the X-axis motion vector component;
• (a-4) applying the first and second X-axis motion vector difference components to second and third buffers, respectively, if it is checked at said step (a-2) that said first buffer is not in the clear state;
• (a-5) storing temporarily the first and second X-axis motion vector difference components into said second and third buffers, respectively, adding the stored first and second X-axis motion vector difference components to the X-axis motion vector component from said first buffer, and then outputting the respective sums as first and second Nth X-axis motion vector components through fourth and fifth buffers, respectively;
• (a-6) allowing a comparator to check whether the first Nth X-axis motion vector component from said fourth buffer is within the range from -31 to 31;
• (a-7) allowing a selector to select the first Nth X-axis motion vector component from said fourth buffer and to output the selected first Nth X-axis motion vector component to said first buffer, if it is checked at said step (a-6) that the first Nth X-axis motion vector component from said fourth buffer is within the range from -31 to 31, and allowing said first buffer to output the first Nth X-axis motion vector component from said selector as an (N-1)th X-axis motion vector component;
• (a-8) allowing said selector to select the second Nth X-axis motion vector component from said fifth buffer and to output the selected second Nth X-axis motion vector component to said first buffer, if it is checked at said step (a-6) that the first Nth X-axis motion vector component from said fourth buffer is not within the range from -31 to 31, and allowing said first buffer to output the second Nth X-axis motion vector component from said selector as the (N-1)th X-axis motion vector component;
• and
• (a-9) setting an X-axis valid signal to 1 synchronously with the output of said first buffer;
• and
• (b) decoding a Y-axis component of the motion vector in response to first and second Y-axis motion vector difference components.

A motion vector decoding method as for converting a variable length coded representation of a motion vector into an original vector using a difference component of the motion vector, comprising the steps of:

• (a) decoding an X-axis component of the motion vector in response to first and second X-axis motion vector difference component;
• and
• (b) decoding a Y-axis component of the motion vector in response to first and second Y-axis motion vector difference components, decoding the Y-axis motion vector component includes the steps of:
• (b-1) checking whether a Y-axis difference valid signal has been inputted, to check whether the first and second Y-axis motion vector difference components have been inputted, the first and second Y-axis motion vector difference components being (N+1)th Y-axis motion vector components;
• (b-2) checking whether a first buffer is in a clear state, if it is checked at said step (b-1) that the Y-axis difference valid signal has been inputted;
• (b-3) setting an output of said first buffer to 0 if it is checked at said step (b-2) that said first buffer is in the clear state and allowing said first buffer to output the Y-axis motion vector component;
• (b-4) applying the first and second Y-axis motion vector difference components to second and third buffers, respectively, if it is checked at said step (b-2) that said first buffer is not in the clear state;
• (b-5) storing temporarily the first and second Y-axis motion vector difference components into said second and third buffers, respectively, adding the stored first and second Y-axis motion vector difference components to the Y-axis motion vector component from said first buffer, and then outputting the respective sums as first and second Nth Y-axis motion vector components through fourth and fifth buffers, respectively;
• (b-6) allowing a comparator to check whether the first Nth Y-axis motion vector component from said fourth buffer is within the range from -8 to 7;
• (b-7) allowing a selector to select the first Nth Y-axis motion vector component from said fourth buffer and to output the selected first Nth Y-axis motion vector component to said first buffer, if it is checked at said step (b-6) that the first Nth Y-axis motion vector component from said fourth buffer is within the range from -8 to 7, and allowing said first buffer to output the first Nth Y-axis motion vector component from said selector as an (N-1)th Y-axis motion vector component;
• (b-8) allowing said selector to select the second Nth Y-axis motion vector component from said fifth buffer and to output the selected second Nth Y-axis motion vector component to said first buffer, if it is checked at said step (b-6) that the first Nth Y-axis motion vector component from said fourth buffer is not within the range from -8 to 7, and allowing said first buffer to output the second Nth Y-axis motion vector component from said selector as the (N-1)th Y-axis motion vector component;
• and
• (b-9) setting a Y-axis valid signal to 1 synchronously with the output of said first buffer.