Mapping GOPS in an Improved DVC to H.264 Video Transcoder - Advanced Concepts for Intelligent Vision Systems - page 21

Mapping GOPS in an Improved DVC to H.264
Video Transcoder
Alberto Corrales-Garcia, Gerardo Fernandez-Escribano, and Francisco Jose Quiles
Instituto de Investigación en Informática de Albacete (I3A)
Universidad de Castilla-La Mancha
02071 Albacete, Spain
{albertocorrales,gerardo,paco}@dsi.uclm.es
Abstract. In mobile to mobile video communications, both transmitter and
receptor should keep low complexity constrains during video compression and
decompression processes. Traditional video codecs have highly complex encoders
and less complex decoders whereas the Wyner-Ziv video coding paradigm
inverses the complexity by using more complex decoders and less complex
encoders. For this reason, transcoding from Wyner-Ziv to H.264 provides a
suitable framework where both devices have low complexity constraints. This
paper proposes a flexible Wyner-Ziv to H.264 transcoder which allows us to map
from a Wyner-Ziv GOP pattern to a I11P H.264 GOP. Furthermore, the
transcoding process is improved when reusing the motion vectors that have been
calculated during the Wyner-Ziv decoding process to reduce the H.264 motion
estimation complexity. Accordingly a time reduction up to 72% is obtained
without significant rate-distortion loss.
Keywords: DVC, Wyner-Ziv, H.264, Transcoding.
1 Introduction
The newest generations of mobile communication systems (such as 4G) offer
attractive services such as video telephony and video conference to mobile users.
These systems provide more advanced types of interactive and distribution services in
which video is one of the most prominent applications for these multimedia
communications. In this kind of services, both the transmitter and receiver devices
may not have sufficient computing power, resources or complexity constraints to
perform complex video algorithms (both coding and decoding). By using traditional
video codecs such as H.264 [1] these low complexity requirements have not been
satisfied because H.264 has high complexity at the encoder side. Therefore, these
mobile video communications that employ traditional video codecs lead to an
inefficient configuration because the encoders sacrifice Rate - Distortion (RD)
performance by using only the lower complexity encoding tools. Distributed Video
Coding (DVC) [2] is a more recent video coding paradigm that offers a video coding
scheme where the majority of the complexity is moved to the decoder which deals
with simpler encoders. Since one year ago, DVC to H.26X transcoders [3][4] have