A highly efficient coding apparatus for coding digital video data comprising: means for receiving the digital video data represented by respective picture element data of first predetermined bits, means for determining at least one elementary picture element for each block, means (41, 43) for predicting values of respective ones of subject picture element data, means for detecting respective predictive errors of the predicted values from the real values of the picture element data, means (45) for determining if each predictive error is greater than a threshold value, means for generating flag data by the output of the determining means, means for gating (214) the elementary picture element data and the subject picture element data for which the respective predictive errors are greater than the threshold value, first and second detecting means (203, 204) for detecting maximum and minimum values, respectively of the output of the gating means in each of the blocks, means (210) for generating dynamic range information for each block from the maximum and minimum values for the respective block, means for generating modified digital video data for each block as the difference between each of the output data of the gating means and one of the maximum and minimum values for the respective block, means for encoding (208) the modified digital video data with a variable digitised bit number determined by the flag data for the respective block so as to provide coded data of variable bit length, thereby the data amount of the coded data for each block can be maintained substantially constant, and transmitting means for transmitting at least the coded data and the flag data.

Highly efficient coding apparatus

At the transmitter side, carrier waves are modulated
according to an input signal for producing relevant signal
points in a signal space diagram. The input signal is
divided into two, first and second, data streams. The
signal points are divided into signal point groups to which
data of the first data stream are assigned. Also, data of
the second data stream are assigned to the signal points of
each signal point group. A difference in the transmission
error rate between the first and second data streams is
developed by shifting the signal points to other positions
in the space diagram. At the receiver side, the first
and/or second data streams can be reconstructed from a
received signal. In TV broadcast service, a TV signal is
divided by a transmitter into two, low and high, frequency
band components which are designated as a first and a second
data stream respectively. Upon receiving the TV signal, a
receiver can reproduce only the low frequency band component
or both the low and high frequency band components, depending
on its capability.

Signal transmission system

Information systems and distributed applications for the Internet show a growing demand for real-time audiovisual services. Support for those services within the Internet protocol layer will be widely available in the near future. Nevertheless, the heterogeneous structure of the Internet remains to be a great obstacle for establishing real-time video services. Scalable video codecs, generating bit-streams decodable at different rates, have been proposed to address the heterogeneity problem. In this article we present a scalable codec based on a spatio-temporal resolution pyramid combined with lattice vector quantization for efficient compression. With this approach additional lower bit-rate layers can be transmitted at the same overall bit-rate as needed by an H.263 single-layer transmission. The complexity of the codec is sufficiently low to allow software-only implementations of Internet video services. This is demonstrated on an Internet video server application.

Scalable video transmission for the Internet

In an Enhanced Definition Television (EDTV) system disclosed here, an assistance signal is transmitted to enable a suitably equipped receiver (105) to choose from a number of predetermined deinterlacin modes. The modes represent interpolation options for estimating lines missing in a current interlaced image field, thereby enhancing the vertical resolution of a display. For example, five options may provide for as follows: (1) intra-frame linear interpolation, (2) use of information from a preceding frame, (3) use of information from a succeeding frame, (4) combining the results of (1) and (2) and (5) combining the results of (1) and (3). Preferably, interpolation options are derived on a block basis and transmitted with coded motion vectors which may be compressed to make maximum use of the available bandwidth. The assistance signal may be transmitted within the vertical and/or horizontal blanking intervals of an interlaced television broadcast.

Digitally assisted motion compensated deinterlacing for enhanced definition television.

This paper deals with the introduction of digital HDTV in such a way that broadcast programs can be picked up by HDTV and TV sets at the same time, with low hardware complexity. This challenging problem, referred to as the compatibility problem in the text, only makes sense as long as it compares well with stand alone schemes in terms of picture quality and hardware complexity. Compatibility requirements mostly have implication on the motion compensation loop of the coding schemes. Proposed schemes are based on subband techniques.

Motion compensated subband coding schemes for compatible high definition TV coding

The coding system described in Part 1 allows compatible coding between various image formats ranging from VT to HDP and including interlaced formats. Interlaced input signals are converted into their ‘progressive equivalent’ before splitting. Compatible coding is based on the so-called Format Independent Splitting (FIS) approach: the same splitting is used whatever the input format except for interlaced inputs, which do not undergo the first horizontal splitting. Temporal correlation must be taken into account to obtain good quality images at bit rates below 1 bit per pel. Nevertheless, the hybrid scheme must be designed carefully in order to keep compatibility capabilities and avoid any drift at the compatible decoder side.

Compatible coding of television images, part 2. Compatible system

This paper describes a multiresolution coding system based on a ‘full subband’ approach. The input image is first split according to a separable hierarchical structure and each resulting band is then independently PCM encoded. In order to obtain quite an optimal coding scheme, subband filters must belong to a particular class of ‘admissible’ filters and the decomposition tree must be chosen carefully.

Compatible coding of television images, part 1. Coding algorithm☆

In the method, the images are represented by a series of digital values quantised according to a quantisation scale, then coded by blocks in inter or intra-image coding mode before being transmitted to a video recorder through a buffer memory. It consists in transmitting the series of digital values by coded groups of images, by placing, at the start of each group, an image coded in intra coding mode and in adjusting (6...19) the quantisation step of the digital values to keep a substantially constant throughput at the output of the buffer memory for these groups of images. Application: digital video recorder.

Yann Thomas

Papers

Compatible coding of television images, part 2. Compatible system

Compatible coding of television images, part 1. Coding algorithm☆

Method and device for regulating variable-throughput image coders/decoders fitted to video recorders