Video quality assessment is an important tool of guaranteeing video services in a required level of quality. Although
subjective quality assessment is more reliable due to the reflection of Human Visual System (HVS) than objective
quality assessment, it is a time-consuming and very expensive approach, and is not appropriate for real-time applications.
Therefore, much research has been made for objective video quality assessment instead of subjective video quality
assessment.
Among three kinds of objective assessment approaches which are
full-reference, reduced-reference and no-reference
methods, no-reference method has drawn much attention because it does not require any reference. The encoding
parameters are good features to use for no-reference model because the encoded bitstreams carry plenty of information
about the video contents and it is easy to extract some coding parameters to assess visual quality.
In this paper, we propose a no-reference quality metric using two kinds of coding parameters in H.264/AVC:
quantization and block mode parameters. These parameters are extracted and computed from H.264/AVC bitstreams,
without relying on pixel domain processing. We design a linear quality metric composed of these two parameters. The
weight values of the parameters are estimated using linear regression with the results of subjective quality assessment
which are obtained based on the DSIS (Double Stimulus Impairment Scale) method of ITU-R BT.500-11.
KEYWORDS: Computer programming, Scalable video coding, Video, Lithium, Quantization, Signal detection, Video coding, Electroluminescence, Communication engineering, Telecommunications
We introduce an efficient mode selection method in the enhancement layers of spatial scalability in the SVC encoder by selectively performing the inter-layer residual coding of the SVC. The proposed method is to make an analysis of the characteristics of integer transform coefficients for the subtracted signals for two residuals from lower and upper spatial layers. Then it selectively performs the inter-layer residual prediction coding in the spatial scalability if the SAD values of inter-layer residuals exceed adaptive threshold values. Therefore, by classifying the residuals according to
the properties of integer-transform coefficients only with the SAD of inter-layer residual signals between two layers, the SVC encoder can perform the inter-layer residual coding selectively, thus significantly reducing the total encoding time with 51.2% in average while maintaining the RD performance with negligible amounts of quality degradation.
KEYWORDS: Video, Video coding, Motion estimation, Computer programming, Visualization, Video compression, Mobile communications, Visual compression, Distortion, Video processing
We propose a fast macroblock mode decision scheme in the H.264|MPEG-4 Part 10 Advanced Video Coding
(AVC) for mobile video telephony applications. In general, the face region around a speaker is considered region of
interest (ROI) while the background is not importantly considered, thus being regarded as non-ROI for the video
telephony situations. We usually have to consider the following two issues: (1) the platforms of mobile video telephony
are usually computationally limited and the AVC codecs are computationally expensive; and (2) the allowed channel
bandwidths are usually very small so the compressed video streams are transmitted with visual quality degraded. In this
paper, we challenge the two issues: Firstly, a fast macroblock mode decision scheme is contrived to alleviate the
computational complexity of H.264|MPEG-4 Part 10 AVC; and secondly, ROI/non-ROI coding of H.264|MPEG-4 Part
10 AVC is incorporated to enhance subjective visual quality by encoding ROI data in higher quality but non-ROI data in
lower quality.
Our proposed fast macroblock mode decision scheme consists of three parts: early skip mode detection, fast inter
macroblock mode decision and intra prediction skip parts. The skip mode detection method is to decide whether or not to
perform the rest inter macroblock modes in P-Slices. The fast inter macroblock mode method is to reduce the candidate
block mode by SATDMOTION from 16x16 and 8x8 block motion estimation. The intra prediction skipping condition is set
to decide whether or not to perform the 4x4 intra prediction in P-Slices using the relation between magnitude of the
motion vectors of the current macroblock and the occurrence frequencies of intra predicted macroblocks. The
experimental results show that the proposed scheme yields up to 51.88% of the computational complexity reduction in
total encoding time with negligible amounts of PSNR drops and bit rate increments, respectively.
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