Image or video encoding and decoding

A method of encoding image or video content within a set of targets, selected from the group consisting of a target time period, a target complexity, a target output quality, and a target output bitrate, using an encoder having a plurality of coding configurations, the method comprising the steps of:

• setting an initial coding configuration in the encoder, where the encoder comprises a plurality of coding tools each having a set of selectable options, where options are selected dynamically for each tool during encoding by testing of options, wherein said coding configurations differ one from the other in the number of options tested for each of one or more tools;
• encoding a first part of the content using the encoder in the initial configuration;
• determining content based usage measures for the initial configuration;
• said content based usage measures for the initial configuration comprising the number of times a specified tool is used and a representative time taken to test an option for that specified tool;
• deriving from those measures predictions of the time difference between the time taken to encode content using the initial coding configuration and the time taken to encode content using at least one other coding configuration in which a different number of options are tested for that specified tool;
• determining from the predictions of the time difference and the given targets a second coding configuration meeting given targets and;
• encoding a second or subsequent part of the content using the second or subsequent coding configuration.