General Instrument Corporation

Harmonic, Inc.

James E Kaye

Paul E Haskell

Arthur C Manansala

DelRae H Gardner

Systems, method, and computer program products for providing multi-channel variable bit-rate video compression are described. In some implementations, video channels can be allocated with bit rates that are set based on a predefined video compression quality. More specifically, each channel can generate a table describing the set of video compression quality values each corresponding to a bit rate value that can be used to achieve that video compression quality value. To generate the table or pre-compression coding information, encoders of the system described herein can pre-encode each input signal at multiple, different bit rates, and record the video compression quality value achievable at each of the bit rates. The system also can use lesser number of encoders for pre-encoding, supplemented by data interpolation, to generate the pre-compression coding information, requiring less processing algorithm but at an expense of lower accuracy.

Multi-channel variable bit-rate video compression

A method and apparatus for bit rate allocation, or statistical multiplexing, in a multi-channel video data encoder. A pre-processor in each channel determines a bit rate need prior to compression and encoding. A control processes the bit rate need in each channel to arrive at an allocated bit rate for each channel. The video data is then compressed and encoded according to the allocated bit rate. The bit rate demand accounts for various characteristics of the current picture data in each channel, including spatial activity, temporal activity, image size, frame rate, scene change, brightness, flash, fade, and horizontal pixel resolution. The system also biases the bit rate allocation according to inter-frame distance, whether the average spatial activity level is below a lower threshold, whether the inter-frame distance is above an upper threshold or below a lower threshold, whether the quantization of previous frames is above an upper threshold, the length of the Group of Pictures (GOP), and a user-selectable priority factor. The system also allocates any surplus bit rate among the channels to avoid having unused bandwidth.

Pre-processing of bit rate allocation in a multi-channel video encoder

A system for remultiplexing packets that are provided at variable rates in digital bitstreams using a delay buffer and rate estimation. A bitstream with specific packet types provided at different rates is extracted from a multiplex and combined with other fixed or variable rate bit streams in such a way that timing delivery constraints on the extracted variable rate bitstream are followed. The extracted bitstream is smoothed to reduce variations in the data rate. The smoothed bitstream is then processed in first and second parallel paths. In the first path, selected packets are discarded to obtain a retained data stream. The data rate of the retained data stream is estimated and provided to a control. In the second path, the smoothed bitstream is delayed according to at least the processing time of the rate estimator in the first path, then the selected packets are discarded to obtain a delayed, retained data stream. The retained data stream in the second path is then remultiplexed with other data streams at a rate near the estimated data rate. For example, the invention is suitable for use at a cable television headend which grooms and remultiplexes digital transport streams that comply with the MPEG-2 standard.

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Pleasanton, CA, United States of America

James E Kaye