Fast H.264 Picture in Picture (PIP) transcoder with B-slices and direct mode support

H.264, the modern standard for video coding, has become increasingly popular in recent years, and offers solutions for many applications requiring video compression. Some of these applications require insertion of content into an already compressed video. This operation incurs high computational cost if a naive approach of full re-encoding is taken. Previous efforts in this field targeted the Baseline Profile of the H.264 standard. The Main Profile, that offers very efficient encoding modes using B-slices and Spatial Direct encoding, has not been addressed. We present Guided Encoding - a novel solution for efficient Picture-in-Picture embedding using the coding parameters of the original compressed bit stream. We also present an algorithm for handling Spatial Direct mode encoding to prevent propagation of errors caused by the embedding of new content into the original sequence. We reduce the computational time by an average factor of five in comparison to performing full re-encoding while preserving the video quality.