Abstract: A method and apparatus for generating region frames from video frames are disclosed which employs an industry standard encoder to lessen the negative impact on the quality of the transmitted video sequence while consuming fewer bits. The method and apparatus utilizes image segmentation and color replacement techniques to create the region frames. Each region frame includes a subject region, zero or more previously segmented regions and zero or more non-subject regions. The subject region is defined by the pixels of the original video frame. The previously segmented regions and non-subject regions are assigned replacement pixels P.sub.n,y and C.sub.n, respectively. The replacement pixel C.sub.n is chosen to indicate a color that is not likely to be confused with any color in the subject region R.sub.n. The replacement pixels P.sub.n,y are chosen such that the compression ratio of the region frame data is maximized.

Abstract: High-resolution, progressive format video signals having high frame rates may be encoded by a base layer encoder and an enhancement layer encoder to provide two kinds of encoded video signals which share a common output channel. These encoded video signals are received at an input of a video receiver which may use one or both of the two kinds of encoded video signal. Relatively lower performance high-definition televisions may thus receive video signals from higher performance transmitters and produce satisfactory pictures. Higher performance HDTVs will be able to utilize the full performance capabilities of these video signals.

Abstract: A method and apparatus for controlling quantization and buffering for video digital signal compression wherein a processor determines a bit budget value based on a number of frames to be skipped and a target buffer fullness. The bit budget value is used to retrieve a default Q-step value from a table of default quantization step size values and corresponding bit budget values. A default Q-step value is used to quantize the input digital signal only if it is less than a maximum. If, however, the default quantization step size value exceeds the maximum, then the number of frames to be skipped and the target buffer fullness may be increased to achieve a lower default quantization step size.

Abstract: Digital video transmission rate matching techniques are disclosed. A bit stream rate matching apparatus includes a bit rate increasing device and a bit rate reducing device. The bit rate increasing device converts a video bit stream having a first transmission rate to a video bit stream having a second transmission rate wherein the first transmission rate is less than the second transmission rate. The bit rate reducing device converts a video bit stream having the second transmission rate to a video bit stream having the first transmission rate. The bit stream rate matching apparatus is useful in the context of a multimedia conference where a first endpoint device employs the first transmission rate and a second endpoint device employs the second transmission rate.

Abstract: The problems associated with slow timing recovery in an ATM receiver are overcome by detecting the transmission rate of a received bit stream and periodically detecting the transmitted Enc.sub.-- CR values, which are used to calculate additional estimated clock reference (Est.sub.-- CR) values between the actual transmitted Enc.sub.-- CR values. The Est.sub.-- CR values are then used along with the actually received Enc.sub.-- CR values to generate a phase locked loop (PLL) error signal (TC.sub.-- ERROR), wherein the PLL is caused to converge more rapidly. In one embodiment, the TC.sub.-- ERROR values are generated for each received cell or packet instead of only for each received Enc.sub.-- CR value and, consequently, timing recovery is significantly speeded up. Additionally, the Est.sub.-- CR values can be adjusted to minimize the effects of lost cells, as well as, drift in the transmission rate.

Abstract: A video sample is selected for transmission only if it differs significantly in amplitude from the sample corresponding to the same spatial point in a previous video frame. An address word which indicates by its value the position of a sample within a video line is transmitted prior to the amplitude of a sample only if the previous sample was not selected for transmission. The amplitudes for selected samples are transmitted in groups preceded by an address word and terminated by a flag word. Frame synchronization is maintained by transmitting a first sync word during the vertical blanking interval. Ordinarily, the first sample in a video line selected for transmission has an address which is lower in value than the address word of the previous sample selected for transmission and, therefore, no line synchronization is necessary.