Error detection using a maximum distance among four block-motion-vectors in a macroblock in a corrupted MPEG-4 bitstream

A method for detecting errors in a current macroblock in a compressed video bitstream comprising:

• parsing a compressed-video bitstream;
• for a current macroblock in a current video object plane:
• determining a number of motion vectors that encode the current macroblock;
• when only one motion vector encodes the current macroblock:
• using the only one motion vector to generate an address to access a memory;
• reading pixels from the memory for the current macroblock;
• moving a location of the pixels read from the memory to a location for the current macroblock in the current video object plane;
• when multiple motion vectors encode the current macroblock:
• executing a predetermined function on the multiple motion vectors to generate a result value;
• comparing the result value to a threshold;
• signaling a macroblock error when the result value meets error criteria indicated by the threshold;
• when the macroblock error is not signaled, using the multiple motion vectors to generate the address to access the memory and reading pixels from the memory for the current macroblock;
• and
• moving a location of the pixels read from the memory to a location for the current macroblock in the current video object plane,
• whereby the macroblock error is detected by executing the predetermined function on the multiple motion vectors for the current macroblock and threshold comparison.

An error-detecting motion-picture-experts group (MPEG) decoder comprising:

• motion-vector means for reading four motion vectors for four blocks in a current macroblock;
• function means for operating on pairs of the four motion vectors to generate a result;
• threshold means for comparing the result to a threshold;
• error signaling means for signaling an error when the result exceeds the threshold;
• pixel fetching means for reading pixels from a memory storing pixels in a previous video object plane using the four motion vectors to generate four addresses for four blocks in the previous video object plane containing pixels for the four blocks in the current video object plane;
• arranging means for storing the pixels for the four block in the memory for the current video object plane,
• whereby the error is signaled when the four motion vectors for the current macroblock cause the threshold to be exceeded.