Abstract: Tape formatting, tracking and trick mode data generation are disclosed for providing trick modes for compressed video stored on a video tape. The tape is formatted so that trick mode data is recorded at normal speed within certain areas delineated by predetermined boundaries that are within a maintainable range of a predetermined ideal scan path of the heads. These boundaries are oblique to the normal speed tracks and define trick mode data areas in which trick mode data may be recorded. To facilitate tracking, sync words and trick mode identification codes are interleaved within the trick mode data areas. During tracking, the heads reproduce the sync words and identification codes, and the identification codes that match the currently utilized trick mode are counted. The count during a current interval is compared to a count during a previous interval or a threshold to determine if the heads have locked onto the ideal scan path or deviated therefrom.

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: Tape formatting, tracking and trick mode data generation provide trick modes for compressed video stored on a video tape. The tape is formatted so that trick mode data is recorded at normal speed within certain areas delineated by predetermined boundaries that are within a maintainable range of a predetermined ideal scan path of the heads. These boundaries are oblique to the normal speed tracks and define trick mode data areas in which trick mode data may be recorded. To facilitate tracking, sync words and trick mode identification codes are interleaved within the trick mode data areas. During tracking, the heads reproduce the sync words and identification codes, and the identification codes that match the currently utilized trick mode are counted. The count during a current interval is compared to a count during a previous interval or a threshold to determine if the heads have locked onto the ideal can path or deviated therefrom.

Abstract: A quantization parameter for use in encoding a region of an image is developed from a) a categorization of the region into one of a predetermined plurality of perceptual noise sensitivity (PNS) classes, b) a level of psycho-visual quality that can be achieved for the encoded version of the image, the level being selected from among a plurality of predetermined levels, and c) a prestored empirically derived model of the relationship between the PNS classes, the psycho-visual quality levels and the values of the quantization parameter. PNS indicates the amount of noise that would be tolerable to a viewer of the region, i.e., the perceptual sensitivity of the region to noise. Some characteristics on which PNS classes may be based are: spatial activity, speed of motion, brightness of the region, importance of the region in a particular context, the presence of edges within the region and the texture of the region, e.g., from "flat" to "highly textured".

Abstract: A dynamic channel allocation unit for specifying a bit rate for each video coder in a set of parallel video coders comprising an overall video coder is disclosed. The dynamic channel allocation unit is supplied from each individual video coder with an average from quantization step size for the previous frame and the average number of bits produced per pel. For the current image frame the dynamic channel allocation unit computes a set of channel sharing factors, i.e., the percentage of the total channel bandwidth to be allocated to a particular video coder. One channel sharing factor is computed for each individual video coder. Individual members of the set of channel sharing factors may be further refined to reflect the prior history of the channel sharing factor for their corresponding coder. Additionally, the set of estimates may be normalized to reflect the actual number of bits that can actually be produced by each individual video coder.

Abstract: A buffer/quantizer controller in a video coder utilizes the average quantization step size employed for the previous frame, the average number of bits produced per pel by the video coder for the image contained in the previous frame and current frame buffer fullness level to obtain an indication of image complexity. A target current frame quantization step size to be employed by the video coder in encoding a current frame is based on the indication of image complexity. Optionally, the target frame quantization step size is adjusted by a mapping procedure, at a predetermined intervals within each frame period, to account for the current buffer fullness. The map employed by the mapping procedure is adjusted in accordance with the target frame quantization step size.