Variable Bit Rate Compression Research Articles

Efficient JPEG 2000 VBR Compression with True Constant Perceived Quality

This paper describes a novel JPEG 2000 variable bit rate (VBR) encoding system for digital cinema that uses visually lossless viewing distance as the image quality metric to provide true constant perceived quality. In this approach, the wavelet coefficients are quantized using a human visual system model so that there are no detectable compression errors when a movie is viewed at the specified viewing distance (or at any greater distance). The compressed codestream includes only the minimum information that is needed to ensure visually lossless quality, so coding efficiency is high. Compression times are also significantly reduced, as compared to typical VBR systems, which results in a more efficient workflow. These benefits are achieved while maintaining full compatibility with the Digital Cinema Initiatives (DCI) compression specifications.

Multi-program video compression using joint bit-rate control

Variable bit-rate compression (VBR) is known to be more efficient than constant bit-rate (CBR) compression. However, since most transmission media convey a constant bit rate, most applications use CBR compression. In multi-program applications, such as satellite and cable television, a technique called joint bit-rate control can be used. With joint bit-rate control the bit rates of individual programs are allowed to vary, but the sum of all bit rates is kept constant. Since a joint control is involved, the encoders should be geographically close. Joint bit-rate control is different from a technique called statistical multiplexing, which is proposed in combination with ATM networks. In this paper, the benefits of joint bit-rate control are studied. This study involves both a theoretical analysis and a verification with experiments. In the experiments a software simulation was used that included the two basic system aspects of joint bit allocation and variable bit-rate buffer management. Both theory and practice indicate that joint bit-rate control gives a significant gain even for a small number of programs. For instance, extra programs can be transmitted over the same channel, e.g. a satellite link, if joint bit-rate control is used.