A method includes receiving, by a receiving device from a transport network, a code block stream that is in a first rate mode and that includes a plurality of code blocks, determining a target code block from the code block stream, where the target code block is a code block received by the receiving device in an inter-packet gap of the code block stream, the target code block includes a first target code block, and the first target code block is a code block of a data type, and/or the target code block includes a second target code block, and the second target code block is a code block of a termination type, and modifying the target code block to modify the target code block to a code block, of an ordered set type, that is in a second rate mode.