In some aspects, methods and systems described herein provide for preparing component videos for combining into a bitstream. An example system may receive a source video. The system may also receive data representing a compression format. The system may encode a reference frame as an intra-coded picture that is sub-divided into intra-coded units. The system may encode the sequence of source frames as a sequence of predictive-coded pictures conforming to the compression format. The sequence may be divided into groups of pictures that include a first predictive-coded picture followed by one or more second predictive-coded pictures. The first predictive-coded picture may be sub-divided into intra-coded units that represent respective portions of a source frame by describing the pixels of the portion so as to simulate intra-coded pictures. The system may concatenate the sequence of predictive-coded pictures after the intra-coded picture so as to produce a bitstream.