Optimal MPEG-2 encoder design for low bit-rate HDTV digital broadcasting

Video watermarks must maintain picture quality and withstand image processing, and resolving the tradeoff between these conflicting requirements has been one of the central problems in research on video watermarking. This paper shows that watermarks are less perceptible where picture contents are moving and proposes a new criterion for measuring watermark imperceptibility from motion vectors and deformation quantities. It also proposes a watermarking method that uses this criterion to allocate watermarks to picture areas adaptively. Experimental evaluation showed that the proposed method reduces degradation in picture quality and that, for the same picture quality after MPEG encoding and decoding, between 30% and 40% more watermarks can be embedded, improving detection reliability after MPEG processing by an average of 9.5%. The proposed method would be most effective when used with MPEG encoders because they already have the necessary motion estimation functions.

The rapid progress in digital transmission technology has spurred demand for developing a technology that supports monitoring of video transmissions. Automating the picture quality assessment process is in particular demand because it currently depends on subjective assessments by human operators and places a heavy burden on them. The authors therefore propose an objective picture quality measurement method that works without reference pictures. In this proposed method, invisible markers are embedded into original pictures by use of the spread spectrum data hiding method. Since the markers are widely spread over the frequency domain, the degradation caused by MPEG compression can be estimated by detecting the extent of marker degradation. Our method is usable regardless of the kind of picture, bitrate, and number of stages of tandem codec connections. The degradation in picture quality caused by the embedded markers is quite small and not perceivable by the human eye. The proposed method is therefore applicable to a wide range of visual transmission services.

MPEG-2 test stream for evaluation the static picture quality of digital television (DTV) should meet both good picture quality and stable bit rate. In this paper, we present a method for generating a high quality test stream to evaluate the static picture quality in DTV receiver. The proposed method is suitable for encoding the static test pattern, such as multiburst and crosshatch, and is based on user-defined quantization and adaptive zero stuffing algorithm. The user-defined quantization is suitable for minimizing the quantization error, which is the reason of degradation of picture quality, and the adaptive zero stuffing algorithm is used to solve the overflow of video buffer verifier (VBV) buffer while encoding process by MPEG-2 encoder. Experimental results show that the average PSNR and the bit rate of the proposed method have more efficient and stable than those of the conventional.

Multichannel digital video broadcasting is now a practical reality. The new services made possible by this technology offer viewers much wider programme choice than current analogue systems. The wide flexibility offered to programme service providers includes the ability to trade the number of active programmes with the bit rates, and hence picture quality, within the capacity bounds of the system. The nature of the compression process is statistical and, when bit rates are minimised to maximise number of channels, occasionally quality compromises may be necessary if the bit rate cannot momentarily sustain quality. It is possible, by dynamic statistically driven allocation of available capacity, to avoid such momentary quality losses and thus improve the efficiency of the transmission system. This paper explores the relationship between picture quality and multiplex management, especially how the statistical nature of the compressed video can be matched to the MPEG packets and their allocation to services during multiplex processing.

Motion JPEG2000 has been developed as a new video coding standard for motion pictures, utilizing the still image coding standard JPEG2000. Motion JPEG2000 specifies a normative bitstream syntax that the decoder must recognize and allows flexible selection of detailed coding parameters at the encoder. The compression performance largely depends, therefore, on the encoder design. However, the simple implementation of JPEG2000 encoder might cause picture quality degradation due specifically to wavelet image coding of interlaced TV signals and unsatisfactory bit assignments. That degradation might then become conspicuous in subjective picture quality especially during low bit-rate coding. To overcome this problem, we investigated an optimal design for a Motion JPEG2000 encoder that can be used for primary distribution applications of HDTV programs, assuming that the available bit-rate is approximately 50 Mbps. Our study introduces advanced key technologies not yet recognized officially. Coding experiments using those technologies confirmed that a significant coding gain was achieved versus conventional encoding schemes.

Rate Control is an important component in a video encoder for date storage or real-time visual communication. In this paper, we will discuss the rate control in MPEG encoder for real-time video communication over Variable Bit Rate (VBR) channel. In interactive video communication, the video transmission is subject to both channel rate constraints and end-to-end delay constraints. Our goal in this paper is to modify the rate control in MPEG-2 encoder and satisfy the rate constraints, and study how to improve the video quality in the scenario of VBR transmission. Here, we employ Leaky- Bucket to describe the traffic parameters and monitor the encoder's output. Depending on the Rate-distortion models developed by us, we present a rate control algorithm to achieve almost uniform distortion both within a frame and between frames in a scene. With adaptive rate-distortion models and additional function of scene detecting, our method can robustly deal with scenes of different statistical characteristics. Comparing to MPEG2 TM5, in real time video communication, we could keep the constant buffer delay while maintain the decoded image quality stable. Furthermore, the bit allocation in our algorithm is more reasonable and controllable. Therefore, our method realized the advantages that advanced by VBR video communication, such as small end-to-end delay, consistent image quality and high channel efficiency.

Improving the Performance of MPEG Compatible Encoding at Low Bit Rates Using Adaptive Neural Networks

Statistical multiplexing is rapidly becoming an integral part of many digital video broadcasting systems. These systems are designed to ensure optimum usage of channel capacity while providing consistent picture quality through the use of automatic bit-rate allocation. The problem of determining the optimal bit-rate to give each channel is no longer an issue for the broadcaster, except to determine the total bandwidth to be allocated to the statistical multiplexer. Broadcasters familiar with their programme mix (e.g. sports, news, etc.), wish to know the implications on picture quality, given parameters such as the number of channels of each type and the total bandwidth available to the system. Furthermore, large broadcasting systems present the opportunity to 'mix and match' the source material, to optimise performance and ensure sustainable picture quality. This paper investigates the statistics of existing satellite broadcasting channels and demonstrates that the various types of programmes exhibit measurable statistical differences in a consistent manner. By taking important coding parameters such as coded picture resolution into account, the paper derives accurate models to predict the performance of such systems through characterisation of the video sources to be multiplexed.

Mosquito noise is a time dependent video compression impairment in which the high frequency spatial detail in video images having crisp edges is aliased intermittently. A new synthetic test pattern of moving spirals or circles is described which generates mosquito noise (MN) under Motion Pictures Expert Group (MPEG) compression. The spiral pattern is one of several NIST-developed patterns designed to stress specific features of compression based on motion estimation and quantization. The 'Spirals' pattern has several spirals or circles superimposed on a uniform background. The frames are filtered to avoid interline flicker which may be confounded with MN. Motion of the spirals and changing luminance of the background can be included to reduce the correlation between successive frames. Unexpectedly, even a static pattern of spirals can induce mosquito noise due to the stochastic character of the encoder. We consider metrics which are specific to the impairment being measured. For mosquito noise, we examine two separable detectors: each consists of a temporal (frame-to-frame) computation applied to the output of a spatial impairment detector which is applied to each frame. The two spatial detectors are: FLATS, which detects level 8 X 8 pixel image blocks; and the root-mean-square (RMS) applied to the image differences between original and compressed frames. The test patterns are encoded at low bit rates. We examine the measured mosquito noise as a function of the Group-of-Pictures (GOP) pattern in the MPEG-2 encoding and find that the GOP structure defines the periodicities of the MN.

The transfer of digital video will be a crucial component of the design of future home networking applications. This transfer was made feasible by the advancement of digital video encoding techniques that reduced the bandwidth required for this transfer to a practical level. MPEG4 is an encoding technique that is suitable for home networking applications with its low bit rate. It also has the advantage that allows viewers to interact with encoded objects. In this paper, we present our work that enables the study of MPEG4 properties and performance on the Internet using simulation. We propose a traffic generator that is able to generate traffic that has almost the same first and second order statistics as an original trace of MPEG4 frames that is generated using an MPEG4 encoder. We model and generate this traffic based on the transform expand sample (TES) methodology using TEStool. We present the model and show the performance of the generator in terms of good matching of the characteristics of the modeled trace.

HDTV CODEC for Digital Recording

As a result of its digital-multimedia initiative, Japan is preparing to introduce digital TV satellite broadcasting. Digital TV broadcasting is based on three scanning methods, namely 525i (480i) and 525p (480p) for SDTV and 1125i (1080i) for HDTV. The current 525i analog TV broadcasting and 1125i Hi-Vision broadcasting can also be performed by simulcast. In this paper, a new image detail creation system is described that enables displaying various kinds of TV-image sources in a single display. The system enables not only attaining a higher picture quality for the current 525i system in which the use of a small number of scanning lines degrades the picture quality but also harmonizing the new 525p and 1125i systems in which many kinds of scanning forms are used that are different from those used in the 525i system. By using an interpolation technique in the system, a 525i interlaced scanning image source can be converted with a double field rate and a double scanning line reducing the degradation due to the conventional interlaced scanning system. In the scanning-conversion procedure, image details and emphasis can be created and interpolated to enable a high-definition image. The display system can be evaluated using a response analysis of the two-dimensional spectrum of temporal frequencies and vertical spatial frequencies.

A new adaptive post-processing algorithm to enhance the quality of a noisy video sequence is presented. This algorithm employs motion compensated frame averaging to improve picture quality. A classification algorithm divides sub-blocks of pixels in the averaged frame into 4 classes: edge, smooth, non-smooth with motion and non-smooth without motion. Spatial algorithms that perform multilevel median filtering, double median filtering and median filtering are used for pixels belonging to edge, smooth and non-smooth with motion categories. Pixels in the nonsmooth, unmoving category are left unfiltered to preserve corresponding image texture. In a simpler version of this 4-class system, the motion cues and motion compensated frame averaging are eliminated, and the purely spatial filtering is based on a 3-class algorithm. When used at the output of a 3-D subband coder at 384 kbps, the spatial postfilter was shown to provide a consistent gain in subjectively evaluated picture quality. Twenty-five viewers participated in an experiment involving three coded sequences. In a pairwise comparison of postfiltered and unfiltered sequences, the postfiltered version was judged to be better in 63 out of 75 instances. >

A new rate control scheme is used to calculate the target bit rate for each frame based on a quadratic formulation of the rate distortion function. The distortion measure are assumed to be either the average quantization scale of a frame or mean square error. The rate distortion function is modeled as a second order function of the inverse of the distortion measure. We presented a closed form solution for the target bit allocation which applies to both the digital storage media (DSM) applications (e.g., MPEG-2) and very low bit rate (VLBR) applications (e.g., MPEG-4). We perform experiments on a wavelet-based coder to demonstrate the versatility of our scheme. Model parameters are estimated using statistical linear regression analysis. Since the estimation uses the past encoded frames of the same picture prediction type (I, P and B pictures), the proposed approach is a single pass rate control technique. For the MPEG-2 coder the fluctuations of the bit counts are significantly reduced by 20 percent to 65 percent in the standard deviation of the bit count while the picture quality remains the same. For the MPEG-4 VM coder, the PSNR is improved by almost one dB as compared to the best MPEG-4 VM rate control using exhaustive combinations of quantization scale parameters.

An efficient mobile video streaming system needs to cope with unstable network bandwidth and limited battery life. We propose a novel streaming system which jointly considers picture quality, bit-rate and energy consumption. Reducing the spatial resolution of a video stream adaptively proves to be more efficient in terms of picture quality and energy consumption than conventional rate control using only adjustment of quantization parameter. We apply the same scheme to scalable coding for large-scale mobile video streaming. This extends the adaptation of an SVC stream to lower bit-rates, while maintaining temporal stability. Our approach has been shown to improve picture quality by approximately 0.5 dB in low bit-rate conditions, and also reduces energy consumption by more than 50% compared to conventional video streaming.