1. A decoder for decoding a prediction mode of a current block, wherein the decoder comprises a regular decoding engine and a bypass decoding engine, the regular decoding engine is used for arithmetic decoding using a context, the bypass decoding engine is used for arithmetic decoding with a bypass decoding process, and wherein the decoder is configured to: decode a flag using the regular decoding engine, wherein the flag indicates whether the prediction mode is derived from a most probable mode list, wherein the most probable mode list comprises one or more candidate prediction modes generated according to prediction modes of one or more adjacent blocks of the current block, and wherein the one or more candidate prediction modes of the most probable mode list belong to multiple prediction modes; derive the prediction mode from the most probable mode list using a first information decoded using the bypass decoding engine, when the value of the flag is equal to a first value; and derive the prediction mode from the multiple prediction modes, except for the one or more candidate prediction modes of the most probable mode list, using a second information decoded using the bypass decoding engine, when the value of the flag is equal to a second value, and wherein the second value is different from the first value.