Abstract: In a digital video network, an encoded multimedia data stream is transmitted over the network to the end user terminal where it is decoded for viewing by a subscriber. The network includes a decoding delay reducer, which processes the encoded multimedia data stream to optimize the multimedia data stream to the operating condition of the digital video network. The optimization of the multimedia data stream enables the end user terminal to decode the encoded multimedia data stream sooner after receipt, which reduces channel change time experienced at the end user terminal due to decoding delay.

Abstract: A method of displaying an image. The method includes aligning a first display relative to a second display. The first and second displays having a differing encoding patterns. The method also includes determining a location in relation between the displays and activating pixels on the displays based on the determined location.

Abstract: Providing a fast channel change function in a digital television system by hierarchically modulating each channel to provide both high priority (long interleave) and low priority (short interleave) signals, wherein a receiver may rapidly demodulate and use information within the low priority signal of a new channel to more rapidly change to the new channel.

Abstract: An apparatus and method for deinterlacing video images with improved slope detection is described. In one exemplary implementation, the apparatus includes an input buffer, a processor, and an output buffer. The input buffer is configured to receive a video stream in an interlaced format. The processor is configured to convert the video stream from the interlaced format to a progressive format. This conversion process includes calculating the slope for a diagonal line of an image at a pixel to-be-interpolated (i.e., at a missing pixel) using a slope protection operation to increase the accuracy of the slope calculation. The output buffer is then configured to transmit the video stream in the progressive format.

Abstract: Technology which facilitates a reduction in time of the presentation of video content after a viewer changes channels is described. Frames of a video stream associated with a channel are analyzed to identify locations of access points in the video stream prior to relaying the video stream to a presentation device. Information indicating the locations of access points is stored. The video stream is then time shifted on a continuous basis and is transmitted to the presentation device which made the request for as long as the presentation device remains tuned to the channel corresponding to the request. A first available frame on or before an access point of the time shifted video stream is selected based on the stored information, which is used to commence the transmission of the time shifted video to the presentation device, which facilitates a more immediate presentation of video content.

Abstract: The payloads of IP packets are checked to actually determine if a packet contains MPEG-2 video rather than using predefined streams or priority levels that are assumed to contain such information as is done in the prior art. More specifically, the “sync” bytes of the MPEG-2 stream are searched for within the IP packet payload, and when a pattern indicative of the sync bytes is found the sync bytes are identified and the packet is determined to contain MPEG-2 video. The sync byte was defined in MPEG-2 for over-the-air broadcasting in order that a television receiver be able to synchronize the MPEG-2 transport stream packets. Note that the MPEG-2 video, e.g., the MPEG-2 transport stream packets, may or may not be incorporated within real time protocol (RTP) packets before being incorporated into the IP packets.

Abstract: De-interlacing is effected by determining the motion at each missing pixel and, then, interpolating the missing lines to convert an interlaced field to a progressive frame. The interpolation employed for luminance is determined through motion detection. If motion is detected in the image field based interpolation is used and if no motion of the image is detected frame interpolation is used. Specifically, the interpolation is determined by employing a motion metric. The motion metric at a missing pixel is defined by using a prescribed combination of pixel luminance value differences. A spatial median filter is then used to remove objectionable noise from the pixel luminance value differences and to fill in so-called “holes” in the image. Indeed, the spatial median filter can be considered as providing a measure of the overall effect of all pixels that make up the object of the image.

Abstract: An apparatus provides digital data representative of a compressed high definition video image signal in a manner such that a conventional video tape recorder (VTR) employing current electrical and mechanical technologies is adaptable for reading this data for display in special modes such as fast forward, reverse and still frame. To minimize the loss of data while the VTR is operating in one of these special modes, the data representative of the high definition image signal is decoded by the apparatus to yield available time slots in the data stream. These time slots are then filled with data which duplicates the most important of the original transmitted data then existing in other time slots in the data stream. This duplicating of the data increases the likelihood that the important picture information will be read by the VTR while operating in a special mode.

Abstract: An improved predictive encoder where the leak signal is a function of the buffer fullness of the encoder. More specifically, the signals stored in the encoder output buffer are further encoded based on the fullness of the buffer, and information about this further encoding is used in determining the leak factor level. In accordance with another improvement, this leak factor level is not constrained to granularity that is imposed by the decoder hardware. Removal of the constraint is accomplished by cycling through a sequence of permissible leak levels that averages at the desired level.

Abstract: The effects of perturbations in a decoder responsive to a signal encoded in a predictive coding schema are reduced by shortening the time needed to converge the decoder's prediction signal to that of the encoder. This is accomplished by temporarily altering the leak factor when it is known that a perturbation is about to manifest itself and by, in some situations, altering the incoming encoded signal itself.

Abstract: A decoder for a modified and improved MPEG signal syntax includes a subtractor responsive to an input signal, a frame buffer responsive to the subtractor, a motion compensator responsive to the buffer and to applied motion vector signals, and a multiplier responsive to frame leak signals and to a modified prediction signal for developing an output signal applied to the subtractor. Furthermore, the decoder includes a processor responsive to the motion compensator and to applied adaptive macroblock leak signals for developing the modified prediction signal. The processor comprises a transform circuit responsive to the motion compensator, a gating template responsive to the transform circuit and the adaptive macroblock leak signals, and an inverse transform circuit responsive to the gating template. The transform circuit operates on 2.times.2 blocks of pixels to form 2.times.2 blocks of transform elements. The gating template is responsive to signals that specify a treatment for 2.times.

Abstract: Blocks of HDTV picture information are selected for transmission at a plurality of channel rates of an HDTV transmitter. The size of each block of HDTV picture information is dependent on a target distortion parameter for the HDTV picture information. As a result of this selection, a portion of each block of HDTV picture information is transmitted at the lower channel rate, with the result that the HDTV transmitter range is maximized while maintaining a picture quality for the resulting HDTV video image.

Abstract: A motion compensated encoder where motion vectors are selected based on the prediction error generated in localized areas of the encoded image and based on an available bit budget. The motion vectors are created by dividing the image into blocks of two sizes and by considering the best mix of large and small size blocks, and their associated motion vectors, that minimize the overall prediction error, within the constraints of the bit budget. For convenience, the image division is arranged so that a given number of small sized blocks forms one large sized block (e.g. 16:1). Also, the block sizes are arranged so that employing only large sized blocks does not exceed the given bit budget, while employing only the small sized blocks does exceed the given bit budget.

Abstract: A quantizer, with quantization control that is sensitive to input signal characteristics and to output buffer fullness responds to an input signal that is divided into blocks and DCT transformed. The transformed signal is analyzed to develop a brightness correction and to evaluate the texture of the image and the change in texture in the image. Based on these, and in concert with the human visual perception model, perception threshold signals are created for each subband of the transformed signal. Concurrently, scale factors for each subband of the transformed signal are computed, and a measure of variability in the transformed input signal is calculated. A measure of the fullness of the buffer to which the quantizer sends its encoded results is obtained, and that measure is combined with the calculated signal variability to develop a correction signal. The correction signal modifies the perception threshold signals to develop threshold control signals that are applied to the quantizer.

Abstract: In a differential PCM encoder, the problem of error perpetuation is solved by leaking a changing, rather than a fixed, fraction of the input signal to the differential PCM. The fraction leaked is sensitive to the characteristics of the signal. In one embodiment the fraction leaked is fixed for a frame in accordance with a chosen characteristic of the frame signal. In another embodiment, the fraction leaked is set in accordance with one function when a chosen characteristic of the frame signal exceeds a given level, and follows another function when the chosen characteristic does not exceed the chosen level. In a still another embodiment, the fraction leaked is set to one of two levels, based on a chosen characteristic of the frame signal.

Abstract: An HDTV receiver design includes a reconstruction section and an inner loop section. The reconstruction section comprises a receiving section for accepting the television receiver's antenna signals, for separating out the component signals from the received signals and for decoding the separated signals. The decoded signals are applied to a quantization decoder that is responsive to vector codebook and to applied quantized vector signals, and the output signals of the quantization decoder are applied to an inverse DCT circuit. The inner loop comprises an adder for adding an estimate signal to the output of the DCT circuit, a frame buffer, a motion compensation circuit that is capable of translating large blocks as well as small blocks and a leak circuit that modulates the output of the motion compensator circuit in accordance with a received leak control signal.

Abstract: Graceful degradation for digitally encoded HDTV signals is achieved by appropriately coding the image to provide a controllable degradation of chosen image characteristics, such as temporal degradation, spatial degradation, and dynamic range degradation. In the temporal degradation approach of this invention, the resolution of movement suffers when noise is introduced. In the spatial degradation approach, the spatial resolution of the image is sacrificed. In the range degradation approach, the dynamic range of the signals is sacrificed. The graceful degradation is achieved by dividing the transmitted signal into two or more parts, such as parts A, B and C. Part A is given the heaviest error-correcting code; part B is given a "medium" error correcting code; and part C the is given the least powerful error correcting code (or perhaps none at all). A receiver that is close to the transmitter most likely receives parts A, B and C.

Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by in a manner removing much of the redundancies in the signal, efficiently encoding the remaining signals, and transmitting the encoded signal in a manner that is most compatible with the applicable standards. Specifically, the television signal is encoded by developing motion vectors that describe the best motion estimate of the image to be transmitted, by developing motion estimation error signals, by encoding these error signals within the same bandwidth as occupied by standard NTSC signals and by transmitting the encoded error signals during periods that correspond to the active scan intervals of the NTSC TV signal. The motion vectors themselves, together with video and control signals, are transmitted during the NTSC retrace period.

Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by removing redundancies in the signal and encoding the remaining signals. In the encoding, a portion of the signals to be transmitted is created in the form of an analog signal or a concatenated plurality of pulse amplitude coded samples (A-signal), and another portion of the signals to be transmitted is created in digital form (D-signal). The D-signal is consigned to a specified portion of the transmitted signal, leaving the remainder of the transmission capacity for the A-signal. When the normally created digital signals do not fully occupy the digital portion, enhanced operation results when selected ones of the analog signals or samples are excised from the A-signal, encoded digitally, and added to the D-signal. The excising of those signals leaves room in A-signal portion to include additional analog signals. This leads to an overall better image reproduction at the receiver.

Abstract: In processor arrays for image processors it is useful to be able to determine which is the "top left" array element having a value above or below a threshold. In the present invention an array of processors includes a number of priority encoder circuits connected to the processors to give the address of the top left array element which has a predetermined significance. Decoder circuits are provided to allow particular processors to be addressed, and methods of counting the number of array elements having a predetermined significance, and of reading data to and from the processors, are also described.