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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Flexible high speed CODEC

HARRIS, under contract with NASA Lewis, has developed a hard decision BCH (Bose-Chaudhuri-Hocquenghem) triple error correcting block CODEC ASIC, that can be used in either a bursted or continuous mode. the ASIC contains both encoder and decoder functions, programmable lock thresholds, and PSK related functions. The CODEC provides up to 4 dB of coding gain for data rates up to 300 Mbps. The overhead is selectable from 7/8 to 15/16 resulting in minimal band spreading, for a given BER. Many of the internal calculations are brought out enabling the CODEC to be incorporated in more complex designs. The ASIC has been tested in BPSK, QPSK and 16-ary PSK link simulators and found to perform to within 0.1 dB of theory for BER's of 10(exp -2) to 10(exp -9). The ASIC itself, being a hard decision CODEC, is not limited to PSK modulation formats. Unlike most hard decision CODEC's, the HARRIS CODEC doesn't upgrade BER performance significantly at high BER's but rather becomes transparent.

Wernlund, James V.↗
NASA NTRS1990

Performance of a low data rate speech codec for land-mobile satellite communications

In an effort to foster the development of new technologies for the emerging land mobile satellite communications services, JPL funded two development contracts in 1984: one to the Univ. of Calif., Santa Barbara and the other to the Georgia Inst. of Technology, to develop algorithms and real time hardware for near toll quality speech compression at 4800 bits per second. Both universities have developed and delivered speech codecs to JPL, and the UCSB codec was extensively tested by JPL in a variety of experimental setups. The basic UCSB speech codec algorithms and the test results of the various experiments performed with this codec are presented.

Gersho, Allen↗
NASA NTRS1990

Evaluation of voice codecs for the Australian mobile satellite system

The evaluation procedure to choose a low bit rate voice coding algorithm is described for the Australian land mobile satellite system. The procedure is designed to assess both the inherent quality of the codec under 'normal' conditions and its robustness under 'severe' conditions. For the assessment, normal conditions were chosen to be random bit error rate with added background acoustic noise and the severe condition is designed to represent burst error conditions when mobile satellite channel suffers from signal fading due to roadside vegetation. The assessment is divided into two phases. First, a reduced set of conditions is used to determine a short list of candidate codecs for more extensive testing in the second phase. The first phase conditions include quality and robustness and codecs are ranked with a 60:40 weighting on the two. Second, the short listed codecs are assessed over a range of input voice levels, BERs, background noise conditions, and burst error distributions. Assessment is by subjective rating on a five level opinion scale and all results are then used to derive a weighted Mean Opinion Score using appropriate weights for each of the test conditions.

Bundrock, Tony↗
NASA NTRS1992

Flexible high speed codec

The project's objective is to develop an advanced high speed coding technology that provides substantial coding gains with limited bandwidth expansion for several common modulation types. The resulting technique is applicable to several continuous and burst communication environments. Decoding provides a significant gain with hard decisions alone and can utilize soft decision information when available from the demodulator to increase the coding gain. The hard decision codec will be implemented using a single application specific integrated circuit (ASIC) chip. It will be capable of coding and decoding as well as some formatting and synchronization functions at data rates up to 300 megabits per second (Mb/s). Code rate is a function of the block length and can vary from 7/8 to 15/16. Length of coded bursts can be any multiple of 32 that is greater than or equal to 256 bits. Coding may be switched in or out on a burst by burst basis with no change in the throughput delay. Reliability information in the form of 3-bit (8-level) soft decisions, can be exploited using applique circuitry around the hard decision codec. This applique circuitry will be discrete logic in the present contract. However, ease of transition to LSI is one of the design guidelines. Discussed here is the selected coding technique. Its application to some communication systems is described. Performance with 4, 8, and 16-ary Phase Shift Keying (PSK) modulation is also presented.

Boyd, R. W.↗
NASA NTRS1988

Development of an 8000 bps voice codec for AvSat

Air-mobile speech communication applications share robustness and noise immunity requirements with other mobile applications. The quality requirements are stringent, especially in the cockpit where air safety is involved. Based on these considerations, a decision was made to test an intermediate data rate such as 8.0 and 9.6 kb/s as proven technologies. A number of vocoders and codec technologies were investigated at rates ranging from 2.4 kb/s up to and including 9.6 kb/s. The proven vocoders operating at 2.4 and 4.8 kb/s lacked the noise immunity or the robustness to operate reliably in a cabin noise environment. One very attractive alternative approach was Spectrally Encoded Residual Excited LPC (SE-RELP) which is used in a multi-rate voice processor (MRP) developed at the Naval Research Lab (NRL). The MRP uses SE-RELP at rates of 9.6 and 16 kb/s. The 9.6 kb/s rate can be lowered to 8.0 kb/s without loss of information by modifying the frame. An 8.0 kb/s vocoder was developed using SE-RELP as a demonstrator and testbed. This demonstrator is implemented in real time using two Compaq 2 portable computers, each equipped with an ARIEL DSP016 Data Acquisition Processor.

Clark, Joseph F.↗
NASA NTRS1989

Digital CODEC for real-time processing of broadcast quality video signals at 1.8 bits/pixel

Advances in very large-scale integration and recent work in the field of bandwidth efficient digital modulation techniques have combined to make digital video processing technically feasible and potentially cost competitive for broadcast quality television transmission. A hardware implementation was developed for a DPCM-based digital television bandwidth compression algorithm which processes standard NTSC composite color television signals and produces broadcast quality video in real time at an average of 1.8 bits/pixel. The data compression algorithm and the hardware implementation of the CODEC are described, and performance results are provided.

Shalkhauser, Mary JO↗
NASA NTRS1989

A forward error correction technique using a high-speed, high-rate single chip codec

The authors describe an error-correction coding approach that allows operation in either burst or continuous modes at data rates of multiple hundreds of megabits per second. Bandspreading is low since the code rate is 7/8 or greater, which is consistent with high-rate link operation. The encoder, along with a hard-decision decoder, fits on a single application-specific integrated circuit (ASIC) chip. Soft-decision decoding is possible utilizing applique hardware in conjunction with the hard-decision decoder. Expected coding gain is a function of the application and is approximately 2.5 dB for hard-decision decoding at 10-5 bit-error rate with phase-shift-keying modulation and additive Gaussian white noise interference. The principal use envisioned for this technique is to achieve a modest amount of coding gain on high-data-rate, bandwidth-constrained channels. Data rates of up to 300 Mb/s can be accommodated by the codec chip. The major objective is burst-mode communications, where code words are composed of 32 n data bits followed by 32 overhead bits.

Boyd, R. W.↗
NASA NTRS1989

Digital codec for real-time processing of broadcast quality video signals at 1.8 bits/pixel

The authors present the hardware implementation of a digital television bandwidth compression algorithm which processes standard NTSC (National Television Systems Committee) composite color television signals and produces broadcast-quality video in real time at an average of 1.8 b/pixel. The sampling rate used with this algorithm results in 768 samples over the active portion of each video line by 512 active video lines per video frame. The algorithm is based on differential pulse code modulation (DPCM), but additionally utilizes a nonadaptive predictor, nonuniform quantizer, and multilevel Huffman coder to reduce the data rate substantially below that achievable with straight DPCM. The nonadaptive predictor and multilevel Huffman coder combine to set this technique apart from prior-art DPCM encoding algorithms. The authors describe the data compression algorithm and the hardware implementation of the codec and provide performance results.

Shalkhauser, Mary JO↗
NASA NTRS1991

Digital CODEC for real-time processing of broadcast quality video signals at 1.8 bits/pixel

Advances in very large scale integration and recent work in the field of bandwidth efficient digital modulation techniques have combined to make digital video processing technically feasible an potentially cost competitive for broadcast quality television transmission. A hardware implementation was developed for DPCM (differential pulse code midulation)-based digital television bandwidth compression algorithm which processes standard NTSC composite color television signals and produces broadcast quality video in real time at an average of 1.8 bits/pixel. The data compression algorithm and the hardware implementation of the codec are described, and performance results are provided.

Shalkhauser, Mary JO↗
NASA NTRS1991

Flexible High Speed Codec (FHSC)

The ongoing NASA/Harris Flexible High Speed Codec (FHSC) program is described. The program objectives are to design and build an encoder decoder that allows operation in either burst or continuous modes at data rates of up to 300 megabits per second. The decoder handles both hard and soft decision decoding and can switch between modes on a burst by burst basis. Bandspreading is low since the code rate is greater than or equal to 7/8. The encoder and a hard decision decoder fit on a single application specific integrated circuit (ASIC) chip. A soft decision applique is implemented using 300 K emitter coupled logic (ECL) which can be easily translated to an ECL gate array.

Segallis, G. P.↗
NASA NTRS1992

Flexible high speed CODEC (FHSC)

This paper describes the on going NASA/Harris FHSC CODEC program. The program objectives are to design and build an encoder decoder that allows operation in either burst or continuous modes at data rates of up to 300 megabits per second. The decoder handles both hard and soft decision decoding and can switch between modes on a burst by burst basis. Bandspreading is low since the code rate is greater than or equal to 7/8. The encoder and a hard decision decoder fit on a single application specific integrated circuit (ASIC) chip. A soft decision applique is implemented using 300 K ECL logic which can be easily translated to an ECL gate array.

Segallis, G. P.↗
NASA NTRS1993

Flexible high-speed CODEC

This report is prepared by Harris Government Communication Systems Division for NASA Lewis Research Center under contract NAS3-25087. It is written in accordance with SOW section 4.0 (d) as detailed in section 2.6. The purpose of this document is to provide a summary of the program, performance results and analysis, and a technical assessment. The purpose of this program was to develop a flexible, high-speed CODEC that provides substantial coding gain while maintaining bandwidth efficiency for use in both continuous and bursted data environments for a variety of applications.

Segallis, Greg P.↗
NASA NTRS1994

Triple-Error-Correcting Codec ASIC

Coder/decoder constructed on single integrated-circuit chip. Handles data in variety of formats at rates up to 300 Mbps, correcting up to 3 errors per data block of 256 to 512 bits. Helps reduce cost of transmitting data. Useful in many high-data-rate, bandwidth-limited communication systems such as; personal communication networks, cellular telephone networks, satellite communication systems, high-speed computing networks, broadcasting, and high-reliability data-communication links.

Jones, Robert E.↗
NASA NTRS2008

Integrated Performance of Next Generation High Data Rate Receiver and AR4JA LDPC Codec for Space Communications

Low-density parity-check (LDPC) codes are the state-of-the-art in forward error correction (FEC) technology that exhibits capacity approaching performance. The Jet Propulsion Laboratory (JPL) has designed a family of LDPC codes that are similar in structure and therefore, leads to a single decoder implementation. The Accumulate-Repeat-by-4-Jagged- Accumulate (AR4JA) code design offers a family of codes with rates 1/2, 2/3, 4/5 and lengths 1024, 4096, 16384 information bits. Performance is less than one dB from capacity for all combinations.Integrating a stand-alone LDPC decoder with a commercial-off-the-shelf (COTS) receiver faces additional challenges than building a single receiver-decoder unit from scratch. In this work, we outline the issues and show that these additional challenges can be over-come by simple solutions. To demonstrate that an LDPC decoder can be made to work seamlessly with a COTS receiver, we interface an AR4JA LDPC decoder developed on a field-programmable gate array (FPGA) with a modern high data rate receiver and mea- sure the combined receiver-decoder performance. Through optimizations that include an improved frame synchronizer and different soft-symbol scaling algorithms, we show that a combined implementation loss of less than one dB is possible and therefore, most of the coding gain evidence in theory can also be obtained in practice. Our techniques can benefit any modem that utilizes an advanced FEC code.

Cheng, Michael K.↗
NASA NTRS2017

An Improved SEL Test of the ADV212 Video Codec

Single-event effect (SEE) test data is presented on the Analog Devices ADV212. Focus is given to the test setup used to improve data quality and validate single-event latchup (SEL) protection circuitry.

Single-event effect (SEE); microelectronic devices↗
NASA NTRS2017

An Improved SEL Test of the ADV212 Video Codec

Single-event effect (SEE) test data is presented on the Analog Devices ADV212. Focus is given to the test setup used to improve data quality and validate single-event latch-up (SEL) protection circuitry.

Single-event effect (SEE); microelectronic devices↗
NASA NTRS2011

Java Image I/O for VICAR, PDS, and ISIS

This library, written in Java, supports input and output of images and metadata (labels) in the VICAR, PDS image, and ISIS-2 and ISIS-3 file formats. Three levels of access exist. The first level comprises the low-level, direct access to the file. This allows an application to read and write specific image tiles, lines, or pixels and to manipulate the label data directly. This layer is analogous to the C-language "VICAR Run-Time Library" (RTL), which is the image I/O library for the (C/C++/Fortran) VICAR image processing system from JPL MIPL (Multimission Image Processing Lab). This low-level library can also be used to read and write labeled, uncompressed images stored in formats similar to VICAR, such as ISIS-2 and -3, and a subset of PDS (image format). The second level of access involves two codecs based on Java Advanced Imaging (JAI) to provide access to VICAR and PDS images in a file-format-independent manner. JAI is supplied by Sun Microsystems as an extension to desktop Java, and has a number of codecs for formats such as GIF, TIFF, JPEG, etc. Although Sun has deprecated the codec mechanism (replaced by IIO), it is still used in many places. The VICAR and PDS codecs allow any program written using the JAI codec spec to use VICAR or PDS images automatically, with no specific knowledge of the VICAR or PDS formats. Support for metadata (labels) is included, but is format-dependent. The PDS codec, when processing PDS images with an embedded VIAR label ("dual-labeled images," such as used for MER), presents the VICAR label in a new way that is compatible with the VICAR codec. The third level of access involves VICAR, PDS, and ISIS Image I/O plugins. The Java core includes an "Image I/O" (IIO) package that is similar in concept to the JAI codec, but is newer and more capable. Applications written to the IIO specification can use any image format for which a plug-in exists, with no specific knowledge of the format itself.

Deen, Robert G.↗