Showing papers on "Enhanced Variable Rate Codec published in 1992"
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TL;DR: A high-quality digital video codec has been developed for the Zenith/AT&T HDTV system that adaptively selects between two transmission modes with differing rates and robustness.
Abstract: A high-quality digital video codec has been developed for the Zenith/AT&T HDTV system. It adaptively selects between two transmission modes with differing rates and robustness. The codec works on an image progressively scanned with 1575 scan lines every 1/30th of a second and achieves a compression ratio of approximately 50 to 1. The high compression ratio facilitates robust transmission of the compressed HDTV signal within an NTSC taboo channel. Transparent image quality is achieved using motion compensated transform coding coupled with a perceptual criterion to determine the quantization accuracy required for each transform coefficient. The codec has been designed to minimize complexity and memory in the receiver. >
15 citations
10 May 1992
TL;DR: The simulation results show that under the condition that there is no interleaving delay, the resulting codec can provide good quality speech at a channel bit error rate as high as 10/sup -2/.<>
Abstract: The performance of an error-protected speech codec for mobile radio applications is investigated. The speech codec is a 4 kb/s variation of the proposed Federal Standard 1016 CELP. The major difference is the use of a trained codebook (as opposed to a stochastic codebook in the proposed standard). The channel codec on the other hand, consists of a bank of rate-compatible punctured Reed-Solomon (RS) codes. The two subsystems are combined in an optimal fashion, according to the sensitivity of the speech elements. This implies that the most sensitive bits are protected by the most powerful RS codes, while the least sensitive bits are (either uncoded or) protected by the least powerful code. The performance of such a combined codec under different sets of system parameters and channel conditions is studied. In all cases, though, the aggregate rate is fixed at about 6.4 kb/s. The simulation results show that under the condition that there is no interleaving delay, the resulting codec can provide good quality speech at a channel bit error rate as high as 10/sup -2/. >
5 citations
25 Jun 1992
TL;DR: A half rate speech/channel codec intended for the TIA technology assessment is described and its performance is presented.
Abstract: A half rate speech/channel codec intended for the TIA technology assessment is described. The requirements for this assessment are an overall bit rate of 6.4 kbps and a frame size of 40 msec. The codec design and its performance is presented. >
2 citations
06 Dec 1992
TL;DR: A video codec based on CCITT's standardized p*64 video coding algorithm and communication protocol has been developed for ISDN H0 rate transmission and can be performed by using residual DSP processing power without the need for any hardware addition.
Abstract: A video codec based on CCITT's standardized p*64 video coding algorithm and communication protocol has been developed for ISDN H0 rate transmission. The codec is fabricated on two 280-mm*280-mm boards and is composed of new DSPs, four kinds of NTSC-CIF (National Television Committee-Common Intermediate Format) mutual conversion LSIs, a transmission codec LSI, and an AD/DA (analog-to-digital/digital-to-analog) hybrid IC. The codec codes and decodes full CIF signs at a rate of 15 frames/s and communicates at an ISDN 384-kb/s rate. Application programs for the codec, such as picture reconstruction capability driven by DSPs in the coder or decoder, can be performed by using residual DSP processing power without the need for any hardware addition. >
1 citations