Abstract
To increase the overall visual quality of the video services without increasing data rate, a human visual system-based video coding, founded on a hierarchy of the video stream in different levels of importance, is developed. Determining these importance levels takes in count three classification criteria: the position of current image in the group of images (image level), the importance of the motion vectors of macroblocks in the current image (macroblock level) and belonging or not of a pixel in a spatial region of interest (pixel level). At the end of this classification process, an interpolation between the results of the three-level selection allows to establish an index of importance for each macroblock of the image to be encoded. This index determines the type of channel coding to be applied to the corresponding macroblock. Tests have shown that the technique presented in this paper achieves better results in PSNR and SSIM (structural similarity) than an equal error protection technique.
Highlights
Many subjective studies and experiences in the fields of human vision and electronic imaging revealed that the human visual system (HVS) tends to focus on a few favorite areas in images or scenes data
We propose to express the visual importance of a macroblock in terms of distortion that would be caused by the loss of this macroblock
For comparing the bit rate generated by this unequal error protection and of equal error protection, the number of bits used to encode each image of GOP was calculated
Summary
Many subjective studies and experiences in the fields of human vision and electronic imaging revealed that the human visual system (HVS) tends to focus on a few favorite areas in images or scenes data. A loss occurred in the region of the image drawing the viewer's attention, causes a bigger discomfort than if it occurs outside of this area. This discomfort can be amplified by the temporal spread of damage related to loss in several images. This phenomenon of propagation is accentuated because of the intensive use of intra and inters images in hybrid video encoders. Because of the high efficiency of the compression, the resulting data is very sensitive to the effects of transmission errors To remedy this problem, the encoding based on the regions of interest was combined with unequal error protection approaches.
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