Showing papers on "Encoder published in 2000"

Analysis of video transmission over lossy channels

Abstract: A theoretical analysis of the overall mean squared error (MSE) in hybrid video coding is presented for the case of error prone transmission. Our model covers the complete transmission system including the rate-distortion performance of the video encoder, forward error correction, interleaving, and the effect of error concealment and interframe error propagation at the video decoder. The channel model used is a 2-state Markov model describing burst errors on the symbol level. Reed-Solomon codes are used for forward error correction. Extensive simulation results using an H.263 video codec are provided for verification. Using the model, the optimal tradeoff between INTRA and INTER coding as well as the optimal channel code rate can be determined for given channel parameters by minimizing the expected MSE at the decoder. The main focus of this paper is to show the accuracy of the derived analytical model and its applicability to the analysis and optimization of an entire video transmission system.

An object oriented video system

Abstract: A method of generating an object oriented interactive multimedia file, including encoding data comprising at least one of video, text, audio, music and/or graphics elements as a video packet stream, text packet stream, audio packet stream, music packet stream and/or grahics packet stream respectively, combining the packet streams into a single self-contained object, said object containing its own control information, placing a plurality of the objects in a data stream, and grouping one or more of the data streams in a single contiguous self-contained scene, the scene including format definition as the initial packet in a sequence of packets. An encoder for executing the method is provided together with a player or decoder for parsing and decoding the file, which can be wirelessly streamed to a portable computer device, such as a mobile phone or a PDA. The object controls provide rendering and interactive controls for objects allowing users to control dynamic media composition, such as dictating the shape and content of interleaved video objects, and control the objects received.

Error resilient video coding techniques

Abstract: We review error resilience techniques for real-time video transport over unreliable networks. Topics covered include an introduction to today's protocol and network environments and their characteristics, encoder error resilience tools, decoder error concealment techniques, as well as techniques that require cooperation between encoder, decoder, and the network. We provide a review of general principles of these techniques as well as specific implementations adopted by the H.263 and MPEG-4 video coding standards. The majority of the article is devoted to the techniques developed for block-based hybrid coders using motion-compensated prediction and transform coding. A separate section covers error resilience techniques for shape coding in MPEG-4.

Line-based, reduced memory, wavelet image compression

Abstract: This paper addresses the problem of low memory wavelet image compression. While wavelet or subband coding of images has been shown to be superior to more traditional transform coding techniques, little attention has been paid until recently to the important issue of whether both the wavelet transforms and the subsequent coding can be implemented in low memory without significant loss in performance. We present a complete system to perform low memory wavelet image coding. Our approach is "line-based" in that the images are read line by line and only the minimum required number of lines is kept in memory. There are two main contributions of our work. First, we introduce a line-based approach for the implementation of the wavelet transform, which yields the same results as a "normal" implementation, but where, unlike prior work, we address memory issues arising from the need to synchronize encoder and decoder. Second, we propose a novel context-based encoder which requires no global information and stores only a local set of wavelet coefficients. This low memory coder achieves performance comparable to state of the art coders at a fraction of their memory utilization.

Stator-flux-oriented control of a doubly-fed induction machine with and without position encoder

Abstract: The control of a doubly-fed induction machine (DFM) with and without the use of a rotor position encoder is examined. First, a stator flux linkage oriented control scheme for power and speed control with a position encoder, shows the high performance control capabilities of this control arrangement and serves as foundation for the sensorless scheme. The power-control method is then applied to a sensorless method, based on a previous control arrangement. This method is then extended to derive a sensorless speed-control mechanism for the DFM. All control schemes are implemented and performed on an experimental test system, comprising two 80C167 microcontrollers and a 2.25 kW wound rotor induction machine.

Reliable video communication over lossy packet networks using multiple state encoding and path diversity

Abstract: Video communication over lossy packet networks such as the Internet is hampered by limited bandwidth and packet loss. This paper presents a system for providing reliable video communication over these networks, where the system is composed of two subsystems: (1) multiple state video encoder/decoder and (2) a path diversity transmission system. Multiple state video coding combats the problem of error propagation at the decoder by coding the video into multiple independently decodable streams, each with its own prediction process and state. If one stream is lost the other streams can still be decoded to produce usable video, and furthermore, the correctly received streams provide bidirectional (previous and future) information that enables improved state recovery for the corrupted stream. This video coder is a form of multiple description coding (MDC), and its novelty lies in its use of information from the multiple streams to perform state recovery at the decoder. The path diversity transmission system explicitly sends different subsets of packets over different paths, as opposed to the default scenarios where the packets proceed along a single path, thereby enabling the end- to-end video application to effectively see an average path behavior. We refer to this as path diversity. Generally, seeing this average path behavior provides better performance than seeing the behavior of any individual random path. For example, the probability that all of the multiple paths are simultaneously congested is much less than the probability that a single path is congested. The resulting path diversity provides the multiple state video decoder with an appropriate virtual channel to assist in recovering from lost packets, and can also simplify system design, e.g. FEC design. We propose two architectures for achieving path diversity, and examine the effectiveness of path diversity in communicating video over a lossy packet network.

Optimal mode selection and synchronization for robust video communications over error-prone networks

Abstract: We describe an effective method for increasing error resilience of video transmission over bit error prone networks. Rate-distortion optimized mode selection and synchronization marker insertion algorithms are introduced. The resulting video communication system takes into account the channel condition and the error concealment method used by the decoder, to optimize video coding mode selection and placement of synchronization markers in the compressed bit stream. The effects of mismatch between the parameters used by the encoder and the parameters associated with the actual channel condition and the decoder error concealment method are evaluated. Results for the binary symmetric channel and wideband code division multiple access mobile network models are presented in order to illustrate the advantages of the proposed method.

Space-time bit-interleaved coded modulation with an iterative decoding strategy

Abstract: A space-time coding approach for wireless communications deploying multiple transmit and multiple receive antennas is presented. The approach is based on the concatenation of a convolutional encoder, a bit interleaver, and a space-time signal constellation mapper that combines multi-level/phase modulation with multiple transmit antennas. The decoding strategy follows an iterative (turbo-like) algorithm where soft information is exchanged between a soft-in soft-out demapper and a soft-in soft-out convolutional decoder. It is applicable with one or more receive antennas, and shows that spectral efficient/reliable communications are possible with few iterations. We address the performance analysis in both block and fast flat Rayleigh fading in order to provide insight into the space-time code construction criteria for the approach that we propose. Finally, simulation results are reported for schemes with 2 bits/s/Hz and 4 bits/s/Hz.

Interactive conference content distribution device and methods of use thereof

Abstract: A multimedia distribution device includes an embedded stream encoder and an embedded stream server for encoding and transmitting, through utilization of streaming technology, audio and video content originating from a videoconference site and received through a network interface, to network-connected terminals. In situations in which the videoconference includes the presentation of slides or other content, the device may include a file conversion engine for converting the presentation content received through a data interface into a standard graphic image format, for synchronous distribution with the audio and video content stream. The multimedia content may be viewed in a multiple-window interface, wherein the audio and video content is presented by a streaming media player, and the presentation content is displayed in a separate window. Additionally, the interface may include an interactive text entry interface, through which the viewer may submit comments or questions to the conference presenters. In an operating architecture that includes a separate remote streaming server and a separate network server, a method of distributing content to a large number of viewers includes continuously transmitting the current and successive presentation images to the network server for caching, whereby the viewer web browser can request and locally cache the images prior to arrival of the associated audio and video content.

LDPC encoder and encoder and method thereof

Abstract: A method of decoding low-density parity-check codes comprises a first step that includes calculating └└rR ml , for each parity check equation, at iteration i−1, in response to a third step. A second step includes decision aided equalizing, at iteration i, in response to the first step. The third step includes calculating └└rQ └m , for each parity check equation, at iteration i in response to the second step, wherein └└rQ └m represents information from bit node l to equation node m, one for each connection, and wherein └└rR ml represents information from equation node m to bit node l, one for each connection.

Turbo code symbol interleaver

Abstract: Advantageous error rate performance, high bandwidth efficiency, low delay and reduced error floor are achieved at an acceptable level of decoding complexity via the use of serial concatenated turbo codes. These are codes for which at least some of the output bits, including at least one redundant bit, provided by a first, outer encoder are, after interleaving, further processed by a second, inner encoder. The interleaver uses as its interleaved elements the bits associated with a particular symbol interval. The resulting data and redundant bits then select a symbol from a predetermined constellation for transmission. In the receiver, the turbo code is decoded using a corresponding number of soft output decoders which operates iteratively in such a way that improved performance as compared to a single encoding can be achieved. The turbo codes can be of various dimensionalities and can be used as a component of a multilevel code to achieve a desired level of bandwidth efficiency.

Turbo code termination

Abstract: Advantageous error rate performance, high bandwidth efficiency, low delay and reduced error floor are achieved at an acceptable level of decoding complexity via the use of serial concatenated turbo codes. These are codes for which at least some of the output bits, including at least one redundant bit, provided by a first, outer encoder are, after interleaving, further processed by a second, inner encoder. The resulting data and redundant bits then select a symbol from a predetermined constellation for transmission. In the receiver, the turbo code is decoded using a corresponding number of soft output decoders which operates iteratively in such a way that improved performance as compared to a single encoding can be achieved. The turbo codes can be of various dimensionalities and can be used as a component of a multilevel code to achieve a desired level of bandwidth efficiency. The turbo codes may be terminated such that after random input data has been applied to the turbo encoder for some number of symbol intervals, data other than random input bits is thereupon applied to the turbo encoder over a sufficient number of symbol intervals so as to bring each of the encoders to a known state.

Coupling-driven signal encoding scheme for low-power interface design

Abstract: Coupling effects between on-chip interconnects must be addressed in ultra deep submicron VLSI and system-on-a-chip (SoC) designs. A new low-power bus encoding scheme is proposed to minimize coupled switchings which dominate the on-chip bus power consumption. The coupling-driven bus invert method use slim encoder and decoder architecture to minimize the hardware overhead. Experimental results indicate that our encoding methods save effective switchings as much as 30% in an 8-bit bus with one-cycle redundancy.

Low-power VLSI design for motion estimation using adaptive pixel truncation

Abstract: Power consumption is very critical for portable video applications such as portable videophone and digital camcorder. Motion estimation (ME) in the video encoder requires a huge amount of computation, and hence consumes the largest portion of power. We propose a novel method of reducing power consumption of the ME by adaptively changing the pixel resolution during the computation of the motion vector. The pixel resolution is changed by masking or truncating the least significant bits of the pixel data, which is governed by the bit-rate control mechanism. Experimental results show that on average more than 4 bits ran be truncated without significantly affecting the picture quality. This results in more than 60% reduction in power consumption.

Error-resilient video transmission using long-term memory motion-compensated prediction

Abstract: Long-term memory prediction extends the spatial displacement vector utilized in hybrid video coding by a variable time delay, permitting the use of more than one reference frame for motion compensation. This extension leads to improved rate-distortion performance. However, motion compensation in combination with transmission errors leads to temporal error propagation that occurs when the reference frames at the coder and decoder differ. In this paper, we present a framework that incorporates an estimated error into rate-constrained motion estimation and mode decision. Experimental results with a Rayleigh fading channel show that long-term memory prediction significantly outperforms the single-frame prediction H.263-based anchor. When a feedback channel is available, the decoder can inform the encoder about successful or unsuccessful transmission events by sending positive (ACK) or negative (NACK) acknowledgments. This information is utilized for updating the error estimates at the encoder. Similar concepts, such as the ACK and NACK mode known from the H.263 standard, are unified into a general framework providing superior transmission performance.

Digital video recorder employing a unique ID to interlock with encrypted video programs stored on a storage device

Abstract: The present invention may be regarded as a digital video recorder (DVR) comprising a storage device for storing an encrypted video program, a unique ID for interlocking the encrypted video program with the digital video recorder, and a cryptography facility. The cryptography facility comprises an encoder, responsive to the unique ID, for encrypting a plaintext video program into the encrypted video program stored on the storage device, and a decoder, responsive to the unique ID, for decrypting the encrypted video program stored on the storage device into the plaintext video program during playback.

Seamless splicing of encoded MPEG video and audio

Abstract: Predictive analysis is performed upon encoded digital motion video (such as an MPEG Transport Stream) to facilitate real-time splicing. The predictive analysis includes estimation of upper and lower bounds of the data levels in a decoder's video and audio buffers for splicing in such a way as to prevent buffer overflow and underflow. This enables buffer management techniques including padding or stuffing, micro-restamping, freeze or repeat of frames, skip or drop of frames, alignment of audio with video. The predictive analysis also includes analysis of the structure of the encoded audio including audio access units (AAUs) and compression windows (AFs), prediction in the compressed domain of initial conditions of the decoder buffer levels for every single Elementary Stream (ES) component of a Transport Stream (TS), and identification of valid splicing In Points and Out Points based on the predicted buffer levels without any special encoder. This permits splicing of different compressed audio types without consideration of the details of the compression mechanism. The predictive analysis may also include recommendations or marking. The analysis is performed on ingest of the data as a pre-processing in preparation for splicing of a new file on early queuing in a data storage system before streaming.

Highly accurate articulated coordinate measuring machine

Abstract: Disclosed is a highly accurate articulated coordinate measuring machine, comprising a revolute joint, comprising a circular encoder wheel, having an axis of rotation; a plurality of marks disposed around at least a portion of the circumference of the encoder wheel; bearing means for supporting the encoder wheel, while permitting free rotation of the encoder wheel about the wheel's axis of rotation; and a sensor, rigidly attached to the bearing means, for detecting the motion of at least some of the marks as the encoder wheel rotates; a probe arm, having a proximal end rigidly attached to the encoder wheel, and having a distal end with a probe tip attached thereto; and coordinate processing means, operatively connected to the sensor, for converting the output of the sensor into a set of cylindrical coordinates representing the position of the probe tip relative to a reference cylindrical coordinate system.

Picture-in-picture and multiple video streams using slice-based encoding

Abstract: A head-end centric system and apparatus for encoding and delivery of realtime and non-realtime content including: a non-realtime content source for providing guide content; a guide encoder (416) for encoding the non-realtime content into encoded non-realtime content; a realtime content source for providing realtime video and audio content; a realtime encoder unit (408) for encoding the realtime video and audio content into encoded realtime video and audio; a remultiplexor for repacketizing the encoded non-realtime content and the encoded realtime video and audio into transport packets; and a re-timestamp unit coupled to the remultiplexer for providing timestamps to be applied to the transport packets in order to synchronize the realtime and non-realtime content therein.

Forward error correction with channel adaptation

Abstract: A transmit-configuration mechanism (52) for configuring an FEC encoder (34) (including an associated interleaver (84)) for changing data channel characteristics Channel information specifying a modulation mode and carriers capable of supporting the modulation mode for the data channel is received by a transmitting network node (12a) for use in a data transmission to a receiving network node (12b) The received channel information is based on a prior data transmission to the receiving network node (12b) over the data channel Configuration values are computed from the received channel information and an amount of data to be transmitted in a data transmission The FEC encoder (34) is configured to operate on the data transmission data amount according to the configuration information

Method for intersymbol interference compensation

Abstract: The intersymbol interference compensation (ISIC) method of the invention comprises an encoding step performed by an encoder and a data estimating step performed a data estimator. The encoder performs at least a trellis encoding of a data sequence using a trellis forward-error-correction (FEC) code to provide an encoded sequence, which is supplied to a channel. The data estimator, which advantageously processes a channel output sequence to arrive at an estimate of the data sequence, comprises at least a template generator for generating templates, a partial equalizer for processing the channel output sequence to provide a partially equalized sequence that is substantially free of precursor ISI, and an ISIC decoder for trellis decoding and ISI compensation. The ISIC decoder computes the branch metric for each current branch based on a single-sided template {circumflex over (q)}(x,y) that accounts for the postcursor ISI in the partially equalized sequence, where x is the vector of symbols associated with the past branch or branches that are connected to the current branch and y is the vector of symbols associated with the current branch. The number of states in the ISIC decoder is determined by the trellis code and is independent of the ISI span of the channel. The invention also provides for techniques for adapting the partial equalizer using the templates, estimating the ISI profile, and updating the templates. In one embodiment of the invention, concatenated coding is employed. In yet another embodiment of the invention, the data estimator employs a decision-directed-ISIC (DD-ISIC) decoder that computes the branch metric for each current branch based on a double-sided template ŝ(x,y,z), where z is the vector of symbols associated with the future branch or branches connected to the current branch and is determined by an interim estimate of the data sequence. A double-sided partial equalizer that removes only some of the precursor and postcursor ISI provides the input to the DD-ISIC decoder, which compensates for the unequalized ISI and performs trellis decoding simultaneously.

Digital video recorder for encrypting/decrypting video programs in segments to facilitate trick play features

Abstract: A digital video recorder (DVR) is disclosed for storing a plaintext video program as an encrypted video program. The DVR comprises a random access storage (RAS) device for storing the encrypted video program in encrypted segments. The DVR further comprises a cryptography facility comprising an encoder for encrypting plaintext segments of the plaintext video program into the encrypted segments stored on the RAS device, and a decoder for randomly and independently decrypting the encrypted segments of the encrypted video program into plaintext segments during playback.

A fast parallel multiplier-accumulator using the modified Booth algorithm

Abstract: This paper presents a dependence graph (DG) to visualize and describe a merged multiply-accumulate (MAC) hardware that is based on the modified Booth algorithm (MBA). The carry-save technique is used in the Booth encoder, the Booth multiplier, and the accumulator sections to ensure the fastest possible implementation. The DG applies to any MAC data word size and allows designing multiplier structures that are regular and have minimal delay, sign-bit extensions, and datapath width. Using the DG, a fast pipelined implementation is proposed, in which an accurate delay model for deep submicron CMOS technology is used. The delay model describes multi-level gate delays, taking into account input ramp and output loading. Based on the delay model, the proposed pipelined parallel MAC design is three times faster than other parallel MAC schemes that are based on the MBA. The speedup resulted from merging the accumulate and the multiply operations and the wide use of carry-save techniques.

Data framing for adaptive-block-length coding system

Abstract: An audio encoder applies an adaptive block-encoding process to segments of audio information to generate frames of encoded information that are aligned with a reference signal conveying the alignement of a sequence of video information frames. The audio information is analized to determine various characteristics of the audio signal such as the occurence and location of a transient, and a control signal is generated that causes the adaptive block-encoding process to encode segments of varying length. A complementary decoder applies an adaptive block-decoding process to recover the segments of audio information from the frames of encoded information. In embodiments that apply time-domain aliasing cancellation (TDAC) transforms, window functions and transforms are applied according to one of a plurality of segment patterns that define window functions and transform parameters for each segment in a sequence of segments. The segments in each frame of a sequence of overlapping frames may be recovered without aliasing artifacts independently from the recovery of segments in other frames. Window functions are adapted to provide preferred frequency-domain responses and time-domain gain profiles.

Computer system for statistical multiplexing of bitstreams

Abstract: A PC-type computer has a system bus (e.g., a PCI bus) configured with a main CPU board, a statistical multiplexing (stat-mux) board, and a plurality of video/audio encoder boards, each configured to receive and compress a corresponding video/audio stream. The stat-mux board performs statistical multiplexing on the different compressed bitstreams to transmit multiple bitstreams over individual shared communication channels. Although each of the boards is configured to the system bus, each encoder board has a digital signal processor (DSP) with a synchronized serial interface (SSI) output port that is directly connected to an SSI input port on a DSP on the stat-mux board (which, in one embodiment, has four such DSPs each with six such SSI input ports). As such, (up to 24) compressed video/audio bitstreams generated on the various encoder boards can be transmitted directly to the stat-mux board without having to go through the system bus. In this way, the computer system can provide statistical multiplexing of low-latency video/audio bitstreams without having to suffer the processing delays associated with conventional transmission over PCI system buses.

The Acadia vision processor

Abstract: Presented is a new 80 GOPS video-processing chip capable of performing video rate vision applications. These applications include real-time video stabilization, mosaicking, video fusion, motion-stereo and video enhancement. The new vision chip, code-named Acadia, is the result of over 15 years of research and development by Sarnoff in the areas of multi-resolution pyramid-based vision processing and efficient computational architectures. The Acadia chip represents the third generation of ASIC technology developed by Sarnoff, and incorporates the processing functions found in Sarnoff's earlier PYR-1 and PYR-2 pyramid processing chips as well as numerous other functions found in Sarnoff-developed video processing systems, including the PVT200. A demonstration board is being implemented and includes two video decoders, a video encoder and a PCI interface.

A real-time single pass variable bit rate control strategy and encoder

Abstract: A real-time single pass variable bit rate control strategy is provided to achieve variable bit rate (VBR) MPEG-2 encoding in a video compression system. For a sequence of frames, the level of encoding difficulty of a video interval (i.e., a group of pictures (GOP)) is determined by a perceptual rate-quantization (C-Q) model. This model assigns a composite (C-Q) curve to each video interval from which the number of bits for the video interval is estimated. The estimation relies on a causal predictive model using the parameters obtained from previously encoded video intervals. The R-Q relationship of each picture type is updated and picture bits are assigned, based on the total rate of the video interval under analysis. Robustness of the variable bit rate control strategy is ensured throughout scene transitions and instabilities by applying, for example, a non-linear median filter, and a low pass filter, respectively.

Transcoding for consumer set-top storage application

Abstract: A consumer set-top terminal (400) and method that receives and stores digital programming services such as television programs for subsequent playback by the user in a manner analogous to a conventional video cassette recorder (VCR). An interface (480) allows the terminal's user to control a transcoding process (427) based on the desired quality level for the transcoded data, e.g., high, medium or low. The transcoding is provided without the expense and complexity of a full encoder. By performing transcoding at the terminal (400), the bit rate of the data can be reduced sufficiently to allow economical storage at the terminal. Moreover, the user can set the quality level to be different for different programs, different parts of the same program, or for different channels.

Matrix improvements to lossless encoding and decoding

Abstract: A lossless encoder and decoder are provided for transmitting a multichannel signal on a medium such as DVD-Audio. The encoder accepts additionally a downmix specification and splits the encoded stream into two substreams, such that a two-channel decoder of meagre computational power can implement the downmix specification by decoding one substream, while a multichannel decoder can decode the original multichannel signal losslessly using both substreams. Further features provide for efficient implementation on 24-bit processors, for confirmation of lossless reproduction to the user, and for benign behaviour in the case of downmix specifications that result in overload. The principle is also extended to mixed-rate signals, where for example some input channels are sampled at 48kHz and some are sampled at 96kHz

Space-time coding and channel estimation scheme, arrangement and method

Abstract: The evolution of high rate data services within future wireless networks will call for new RF access technologies to enable substantial increases in overall system spectral efficiency at an acceptably low cost to the user. Space-Time Coding (STC) is an antenna array processing technology currently simulating considerable Interest across the wireless industry. The invention provides a space-time coding apparatus having an input, a trellis encoder, a modulator, a demultiplexer, and a set of signal outputs wherein the input is operable to receive a stream of data. This allows de-multiplexing to take place after coding and modulation has been performed. The trellis encoder comprises a convolutional encoder operable to sequentially group data to provide coded bits to provide QPSK symbols. By the selection of convolutional encoder rates and/or modulation alphabets STCs of any desired dimensionality may be produced including multi-dimensional codes.