Video coding

A computing device comprising a processor and memory, wherein the computing device implements a video decoder configured to perform operations comprising:

• receiving encoded data in a bit stream for a current frame in a sequence of video frames, wherein the current frame includes multiple blocks that are different portions of the current frame, the encoded data in the bit stream including, for each given block among the multiple blocks of the current frame, identifying information in the bit stream for the given block that indicates how to derive motion vector (“MV”) information for the given block, wherein the identifying information in the bit stream for the given block is separate from the identifying information in the bitstream for other blocks among the multiple blocks of the current frame;
• and
• decoding the current frame, including, for each given block among the multiple blocks of the current frame, decoding the given block using motion compensation without using MV information in the bit stream for the given block but according to the identifying information in the bit stream for the given block, wherein:
• if the identifying information in the bit stream for the given block indicates motion projection is used for the given block, the MV information for the given block is derived using MV information of a block of another frame in the sequence of video frames;
• and
• if the identifying information in the bit stream for the given block indicates spatial prediction is used for the given block, the MV information for the given block is derived using MV information for one or more surrounding blocks of the current frame.

One or more computer-readable memory or storage devices having stored thereon encoded data in a bit stream, the encoded data having been produced by operations comprising:

• encoding a current frame in a sequence of video frames, wherein the current frame includes multiple blocks that are different portions of the current frame, and wherein the encoding the current frame includes, for each given block among the multiple blocks of the current frame, encoding the given block using motion compensation without using motion vector (“MV”) information in the bit stream for the given block but according to identifying information in the bit stream for the given block, wherein the identifying information in the bit stream for the given block indicates how to derive the MV information for the given block, and wherein:
• if the identifying information in the bit stream for the given block indicates motion projection is used for the given block, the MV information for the given block is derived using MV information of a block of another frame in the sequence of video frames;
• and
• if the identifying information in the bit stream for the given block indicates spatial prediction is used for the given block, the MV information for the given block is derived using MV information for one or more surrounding blocks of the current frame;
• and
• outputting encoded data for the current frame in the bit stream, wherein, for each given block among the multiple blocks of the current frame, the encoded data in the bit stream includes the identifying information in the bit stream for the given block that indicates how to derive the MV information for the given block, and the identifying information in the bit stream for the given block is separate from the identifying information in the bitstream for other blocks among the multiple blocks of the current frame.