Embodiments of this application provide a video encoding method, a video decoding method, and an apparatus, and relate to the field of image processing technologies. The video encoding apparatus may obtain source data, where the source data includes first high dynamic range HDR data and a first standard dynamic range SDR bitstream for same video data; map reconstructed data of the first SDR bitstream to second HDR data based on a correspondence between the reconstructed data of the first SDR bitstream and the first HDR data; determine a target residual value between the second HDR data and the first HDR data, where a bit width of the target residual value is less than or equal to a first bit width, and the first bit width is a data bit width for encoding a first SDR video into the first SDR bitstream; encode the correspondence and the target residual value, to determine preset data; and transmit the first SDR bitstream to which the preset data is added. In this application, good processing on an SDR video decoding device and an HDR video decoding device can be ensured based on the preset data and the SDR bitstream.