1. Field of the Invention
The present invention relates to signal processing, and, in particular, to computer-implemented processes and apparatuses for encoding and decoding image signals for progressive transmission and display.
2. Description of the Related Art
Still images and video images typically require large numbers of bits to represent digitally, even using sophisticated compression techniques. The time required to transmit such images for display at a remote destination, and therefore the time delay between display of successive images, may prove disturbing to the remote viewer. Using a conventional progressive transmission technique, such as those based on the wavelet transform, may prove computationally intensive and therefore time consuming.
It is desirable to provide encoding systems for generating, encoding, and transmitting image signals and decoding system for receiving, decoding, and displaying image signals that reduce the delay to the remote viewer. In particular, it is desirable to provide personal computer (PC) based conferencing systems that provide the capabilities for efficient transmission of images from one conference participant to a remote conference participant over relatively low bandwidth media, such as a PSTN telephone line.
It is, therefore, an object of the present invention to provide computer-implemented processes and apparatuses for efficiently generating, encoding, and transmitting image signals and methods, apparatuses, and systems for efficiently receiving, decoding, and displaying image signals.
It is a particular object that the present invention be applicable to PC-based conferencing systems.
Further objects and advantages of this invention will become apparent from the detailed description of a preferred embodiment which follows.
The present invention is a computer-implemented process and apparatus for encoding image signals. According to a preferred embodiment, a location within an image is selected and signals corresponding to the image are encoded following a spatial decomposition pattern, wherein the spatial decomposition pattern is based on the selected location.
The present invention is also a computer-implemented process and apparatus for displaying encoded image signals corresponding to an original image. According to a preferred embodiment, an initial set of encoded image signals is provided and a display image is displayed in accordance with the initial set of encoded image signals. A sequence of subsequent sets of encoded image signals is provided and the display image is progressively updated in accordance with the sequence, wherein the sequence corresponds to a spatial decomposition pattern based on a selected location within the original image.
The present invention is also a computer-implemented process and apparatus for transmitting image signals corresponding to an original image at a local node for display at a remote node. According to a preferred embodiment, a location within the original image is selected at the local node. The image is divided into a plurality of blocks at the local node and a transform is applied to each of the blocks to generate a plurality of transformed blocks at the local node, wherein each of the transformed blocks comprises a DC transformed signal and a plurality of AC transformed signals. The DC transformed signals for all of the transformed blocks are encoded to generate encoded DC transformed signals at the local node and the encoded DC transformed signals are transmitted from the local node to the remote node. The encoded DC transformed signals are decoded at the remote node to generate decoded DC transformed signals and a display image is displayed in accordance with the decoded DC transformed signals on a monitor at the remote node. The AC transformed signals for all of the transformed blocks are encoded following a spatial decomposition pattern at the local node to generate a sequence of encoded AC transformed signals, wherein the spatial decomposition pattern is based on the selected location, and the sequence of encoded AC transformed signals is transmitted from the local node to the remote node. The sequence of encoded AC transformed signals is decoded at the remote node to generate a sequence of decoded AC transformed signals and the display image is progressively updated in accordance with the sequence of decoded AC transformed signals.