One of the most frequently used coding mode in H.264 is skip mode. In the conventional approach, after the best RD
mode has been computed and the resultant predicted error coefficients block is all quantized to zero, it is switched to
skip mode. This is a waste of computational resources because skip mode doesn't require forward transform and
quantization. In this paper, skip mode condition is checked for the macroblock prior to multi-block motion estimation.
Motion estimation will not be performed if the condition is satisfied which will drastically reduce the computations. The
condition considers zero-block property after 4x4 block transform/quantisation and caters for noise inherent in natural
video images. In addition, color components are also taken into consideration for skip mode decision. The experimental
results show that the approach can improve encoder speed greatly with negligible bit rate increase or PSNR degradation.
In this paper, the conformance of hypothetical reference decoder (HRD) is addressed for H.264 when there is jitter among the transmission of packets via a channel without packet loss but variation among transmission delay. The sending rate is decoupled
from the coding one. Both the jitter and the total size of coded bitstream are taken into consideration such that the values of buffer size and initial buffer delay are minimized, especially
when the sending rate is greater than the coding one. Sufficient conditions are derived for the conformance of a coded bitstream to a HRD at the constant delay. These conditions are then used to design iterative algorithms to determine a minimal buffer size and a minimal initial buffer delay for the decoder. A novel
interpolation method is also presented such that it is suitable for a wide range of sending rates.
In this paper, we propose an interesting scheme to obtain a good tradeoff between motion information and
residual information for medium granular scalability (MGS). In this scheme, both motion information and residual
information are refined at enhancement layers when the scalable bit rate range is wide, whereas only residual
information is refined when the range is narrow. In other words, for the case of wide bit rate range, there can
be more than one motion vector fields (MVFs) where one is generated at base layer and others are generated at
enhancement layers. When it is narrow, only one MVF is necessary. The layers can either share one MVF or have
its own, depending on the bit rate range cross layers. Unlike Coarse Granular Scalability (CGS), the correlation
between two adjacent MVFs in MGS is very strong. Hence MGS can be provided in the most important bit
rate range to achieve a better tradeoff between motion and residual information and a finer granularity in that
range. CGS can be applied in less important bit rate ranges to give a coarse granularity. Experimental results
show that the coding efficiency can be improved by up to 1dB compared with existing SNR scalability scheme
at high bit rate.
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