3 research outputs found
On the Effectiveness of Video Recolouring as an Uplink-model Video Coding Technique
For decades, conventional video compression formats have advanced via incremental improvements with
each subsequent standard achieving better rate-distortion (RD) efficiency at the cost of increased encoder
complexity compared to its predecessors. Design efforts have been driven by common multi-media use cases
such as video-on-demand, teleconferencing, and video streaming, where the most important requirements are
low bandwidth and low video playback latency. Meeting these requirements involves the use of computa-
tionally expensive block-matching algorithms which produce excellent compression rates and quick decoding
times.
However, emerging use cases such as Wireless Video Sensor Networks, remote surveillance, and mobile
video present new technical challenges in video compression. In these scenarios, the video capture and
encoding devices are often power-constrained and have limited computational resources available, while the
decoder devices have abundant resources and access to a dedicated power source. To address these use cases,
codecs must be power-aware and offer a reasonable trade-off between video quality, bitrate, and encoder
complexity. Balancing these constraints requires a complete rethinking of video compression technology.
The uplink video-coding model represents a new paradigm to address these low-power use cases, providing
the ability to redistribute computational complexity by offloading the motion estimation and compensation
steps from encoder to decoder. Distributed Video Coding (DVC) follows this uplink model of video codec
design, and maintains high quality video reconstruction through innovative channel coding techniques. The
field of DVC is still early in its development, with many open problems waiting to be solved, and no defined
video compression or distribution standards. Due to the experimental nature of the field, most DVC codec
to date have focused on encoding and decoding the Luma plane only, which produce grayscale reconstructed
videos.
In this thesis, a technique called “video recolouring” is examined as an alternative to DVC. Video recolour-
ing exploits the temporal redundancies between colour planes, reducing video bitrate by removing Chroma
information from specific frames and then recolouring them at the decoder.
A novel video recolouring algorithm called Motion-Compensated Recolouring (MCR) is proposed, which
uses block motion estimation and bi-directional weighted motion-compensation to reconstruct Chroma planes
at the decoder. MCR is used to enhance a conventional base-layer codec, and shown to reduce bitrate by
up to 16% with only a slight decrease in objective quality. MCR also outperforms other video recolouring
algorithms in terms of objective video quality, demonstrating up to 2 dB PSNR improvement in some cases
Algorithms & implementation of advanced video coding standards
Advanced video coding standards have become widely deployed coding techniques used in numerous products, such as broadcast, video conference, mobile television and blu-ray disc, etc. New compression techniques are gradually included in video coding standards so that a 50% compression rate reduction is achievable every five years. However, the trend also has brought many problems, such as, dramatically increased computational complexity, co-existing multiple standards and gradually increased development time. To solve the above problems, this thesis intends to investigate efficient algorithms for the latest video coding standard, H.264/AVC. Two aspects of H.264/AVC standard are inspected in this thesis: (1) Speeding up intra4x4 prediction with parallel architecture. (2) Applying an efficient rate control algorithm based on deviation measure to intra frame. Another aim of this thesis is to work on low-complexity algorithms for MPEG-2 to H.264/AVC transcoder. Three main mapping algorithms and a computational complexity reduction algorithm are focused by this thesis: motion vector mapping, block mapping, field-frame mapping and efficient modes ranking algorithms. Finally, a new video coding framework methodology to reduce development time is examined. This thesis explores the implementation of MPEG-4 simple profile with the RVC framework. A key technique of automatically generating variable length decoder table is solved in this thesis. Moreover, another important video coding standard, DV/DVCPRO, is further modeled by RVC framework. Consequently, besides the available MPEG-4 simple profile and China audio/video standard, a new member is therefore added into the RVC framework family. A part of the research work presented in this thesis is targeted algorithms and implementation of video coding standards. In the wide topic, three main problems are investigated. The results show that the methodologies presented in this thesis are efficient and encourage