Encoder, a decoder and corresponding methods for inter prediction

An apparatus for inter prediction comprising:

• a parsing module, configured to parse a first index from a bitstream, wherein the first index is used to obtain prediction information of a first prediction sub-block, wherein a current block comprises the first prediction sub-block and a second prediction sub-block;
• and
• parse a second index from the bitstream;
• a locating module, configured to compare the first index with the second index;
• and
• adjust the second index if the second index is equal to or greater than the first index;
• and
• an obtaining module, configured to obtain prediction information of the second prediction sub-block according to the adjusted second index.