Lucent Technologies Inc.

Lucent Technology

Richard Joseph Pauls

Michael Charles Recchione

The present invention is a method for improving data transfer performance over communications networks connecting data networks and users using adaptive communications formatting. Adaptive communications formatting includes encoding (or compressing) the data and applying error control schemes to reduce the amount of data being transmitted and to correct and/or conceal errors occurring during data transmission. In one embodiment, the present invention uses a set of transcoding techniques to encode (or compress) the data and a set of error control schemes to correct and/or conceal errors occurring during data transmission. The particular sets of transcoding techniques and error control schemes selected to format the data are adaptive to factors, such as the nature of the communications network connecting a user to an access server on the data network, the preferences of the user, and the data type of the data being transmitted to the user (or the access server).

Adaptive communications transcoding and error control

A method of compressing a source (e.g., a video signal, a still image, an audio signal, etc.) is disclosed that does not require the transmission of changes in the quantization step size and more evenly affects the fidelity of the source than techniques in the prior art that change the quantization step size at various points in the compression process. An illustrative embodiment of the present invention involves transforming a source (e.g., a video frame, audio sample, etc.) into m coefficients, in well-known fashion, wherein each of the m coefficients is represented by a known number of bits. Then, only n of the m coefficients are used for transmission or storage, as appropriate, where the n coefficients are more perceptually significant than the m&mdash;n coefficients not used.

Perceptual compression and robust bit-rate control system

Error recovery is improved in a video transmission system by maintaining, for block positions in a frame, a metric whose value for a given block position is indicative of the relative importance of the given block position in determining decoded video quality. The blocks may be macroblocks configured in accordance with a motion-compensated video compression technique such as MPEG-2. The metric values are used to determine one or more of the block positions which are more likely than other block positions to improve decoded video quality if refreshed. The video signal is then refreshed by transmitting intra-coded blocks for the determined block positions in a given frame. The metric may be based on a count of the number of times a block from a given block position has been coded and transmitted since it was last refreshed, such that the block positions having the highest counts are refreshed. The metric-based selection of refresh blocks ensures that the refresh bits are allocated to the blocks most likely to improve decoded video quality.

Method and apparatus for improved error recovery in video transmission

The invention discloses techniques for providing automatic retransmission query (ARQ) functions in a communication system. A transmitter in the system applies an input data packet to a first convolutional encoder operating at a first rate to generate an inner code including multiple encoded packets. The encoded packets are interleaved and applied to a second convolutional encoder operating at a second rate which generates an outer code including a transmit packet generated from each of the encoded packets. A first transmit packet is sent to a receiver, which decodes the transmit packet in a Viterbi decoder operating at the second rate to generate a decoded version of the first transmit packet. The decoded version is inverted to provide a first provisional decoding of the input packet. If a cyclic redundancy code (CRC) check of the first provisional decoding is passed, the receiver sends an ACK signal to the transmitter and no retransmission is required. If the check is not passed, the transmitter sends one or more additional transmit packets, which are processed in a manner similar to the first transmit packet to generate one or more additional provisional decodings of the input data packet. If a CRC check of a given one of these additional provisional decodings is passed, the receiver accepts it as the input packet and sends an ACK signal to the transmitter. If none pass the CRC check, the receiver may combine decoded versions of the transmit packets, and apply the result to a Viterbi decoder operating at the first rate to generate another provisional decoding of the input packet. This provisional decoding is accepted as the input packet if it passes a CRC check.

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Newton, NJ, United States of America

Richard Joseph Pauls