A quantization level is selected for the current video frame in accordance with a plurality of mappings, wherein each mapping correlates an activity measure with a bits per frame measure and each mapping corresponds to a quantization level of a plurality of quantization levels. The current video frame is encoded in accordance with the selected quantization level.
CROSS-REFERENCES TO RELATED APPLICATIONS
This is a continuation-in-part of co-pending application Ser. No 08/158,855, filed on Nov. 24, 1993, entitled "Computer-Implemented Process and System for Decompressing a Compressed Image," the entire disclosure of which is incorporated herein by reference.
The present invention provides a method (200) and device (300) for error control of a video compressed sequence in which error protection for both random and burst channel errors is provided. The error control syntax (100) applies a fixed length packet synchronization system to variable length coded compressed video data, which provides the capability to limit error propagation within the decoded video bit stream. The fixed length packet control information provides information to decode compressed video data in both forward and reverse directions to allow for the recovery of correctly decoded video data within a decoded frame after long bursts of channel errors while reducing the overhead for error control. The error control method also provides video error detection which may be used for error concealment.
A method of filtering and encoding video data in a compressed format is provided. The method includes receiving pixels representing video data from an initial video display, receiving pixels representing video data from a subsequent video display, selecting a group of pixels from the subsequent video display as new video data, determining filtered pixel values from the new video data, and encoding the filtered values in a compressed format for communication to another computer accessible via a computer network.
For video compression processing, each frame in a video sequence is segmented into one or more different regions, where the macroblocks of each region are to be encoded using the same quantizer value, but the quantizer value can vary between regions in a frame. For example, for the videophone or video-conferencing paradigm of one or more "talking heads" in front of a relatively static background, each frame is segmented into a foreground region corresponding to the talking head, a background region corresponding to the static background, and an intervening transition region. An encoding complexity measure is generated for each macroblock of the previous frame using a (e.g., first-order) rate distortion model and the resulting macroblock-level encoding complexities are used to generate an average encoding complexity for each region. These region complexities are then used to select quantizer values for each region in the current frame, e.g., iteratively until the target bit rate for the frame is satisfied to within a specified tolerance range. The selected quantizer values may be modified based on spatial and/or temporal constraints to satisfy spatial requirements of the video compression algorithm and/or to provide temporal smoothness in quality, respectively.
An image reproducing apparatus has a detection circuit for detecting a component difference between groups of encoded image data, a decode circuit for decoding the image data, a regulation circuit for regulating a component of the image data, and a control circuit for controlling the regulation circuit on the basis of a result of detection made by the detection circuit.
A method and apparatus for selecting a quantizer scale for each macroblock within a frame to optimize the coding rate is presented. A quantizer scale is selected for each macroblock within each frame such that the target bit rate for the frame is achieved while maintaining a uniform visual quality over the entire frame.
