 While the video coding format must support such compression across frames in the bitstream format, by not needlessly mandating specific algorithms for finding such block-matches and other encoding steps, the codecs implementing the video coding specification have some freedom to optimize and innovate in their choice of algorithms.For example, section 0.5 of the H.264 specification says that encoding algorithms are not part of the specification.Free choice of algorithm also allows different space–time complexity trade-offs for the same video coding format, so a live feed can use a fast but space-inefficient algorithm, while a one-time DVD encoding for later mass production can trade long encoding-time for space-efficient encoding.