Showing papers by "Zoran Corporation published in 1993"

Parallel encoding/decoding of dct compression/decompression algorithms

Abstract: Encoding and decoding speed in using DCT and IDCT algorithms is enhanced by parallel operation of coding and decoding devices. A frame of image data can be vertically sliced with each slice operated on by a dedicated encoding device and with the encoded slice data concatenated to form the encoded frame of data. Decoding speed is increased by using a plurality of decoding devices in parallel with each decoder having a Huffman decoder and a coefficient dequantizer through which all coded data flows. Only assigned blocks of data are operated on by the IDCT unit in each decoder. Each decoder device can have a plurality of IDCT units for operating on assigned blocks of data.

Image compression coder having improved bit rate control and block allocation.

Abstract: A method of bit rate control and block allocation for discrete cosine transform (DCT) image signal compression includes the steps of (a) partitioning the image signals in blocks (b) calculating DCT coefficients in all blocks, (c) obtaining a measure of block activity (BACT) for each block based on DCT coefficients and for the total image activity (ACT) as a sum of the measures of all block activity, (d) determining a code allocation factor (AF) for each block based on the ratio of block activity (BACT) to target code volume (TCV data) for the coded image date, and (e) allocating bits for each block using the allocation factor (AF) for each block and the target code volume (DCV data). Steps (a-d) are carried out with a first statistical pass through the image data, and step (e) is carried out in a second compression pass through the image data.

Ghost signal cancellation system using feedforward and feedback filters for television signals

Abstract: Disclosed is a television ghost cancellation system based on digital filtering. A baseband video signal at the output of the demodulator is lowpass filtered before being digitized at an analog-to-digital converter. The signal is then processed in digital filters to remove the ghosts. The clean digital signal is then passed to a digital-to-analog converter and lowpass filter to become a clean baseband video signal. The digital filters consist of a feedforward section and a feedback section. The coefficients of the digital filters are calculated by digital signal processor, which processes the data stored in First-In-First-Out buffers (FIFOs). The FIFOs are used as outputs, while one FIFO is used as input to the feedback section. The FIFO stores the standard ghost canceler reference (GCR) signal. Switches are controlled by a synchronization separation circuitry. The coefficients of the feedforward section are estimated by processing data stored in the FIFO. The coefficients of the feedback filter are estimated by adapting a virtual finite impulse response (FIR) filter, which processes data stored in the FIFOs. A scheme is provided to optimize the adaptation process. The advantages of this system are stability and efficiency of the feedback section, fast cancellation and small residuals after convergence.

Image compression coder having improved scale factor control

Abstract: Disclosed is an image compression coding device in which time domain image data is transformed to frequency domain data and then compressed by multiplying the frequency domain data by quantization coefficients scaled by a scale factor based on a non-linear relationship of log(ACVdata) versus log(SF). One or more statistical passes are made through the frequency domain data using initial scale factors in which ACV data is obtained based on the newly defined relationship. The New Scale Factor (NSF) is then calculated based on the initial scale factors (ISF1, ISF2), the accumulated code volumes for the two scale factors (ACVdata1, ACVdata2), and the target code volume (TCV) of the compressed file.

A ghost cancelation system for the NTSC television

Abstract: A ghost canceler for the NTSC television system is described. A three-chip digital filter with a total of 648 taps is used to adaptively cancel the ghosts. An external digital signal processor analyzes the ghosting scenario and provides the optimal set of coefficients for the filter. An interrupt driven scheme is designed to minimize the system memory requirement even when a large number of samples are needed to reduce noise. The tests show that the system can cancel the off-the-air ghosts with good performance. >

Ghost signal cancellation system for television signals

Abstract: A ghost cancellation system for filtering out ghosts in a received video signal including an active filter (14) having a filtering function defined by a first set of coefficients (akold) and having an input and an output. A transmitted ghost cancellation reference (GCR) signal is applied to the input of the active filter during a vertical blanking period to generate a filtered GCR signal at the output of active filter. The filtered GCR signal is compared with a ghostless GCR signal to obtain an error signal, and the filter coefficients are adjusted based on the error signal to obtain a set of new coefficients (aknew). The active filter includes a feedforword FIR filter (14-1) and an adder (14-3) serially connected between the input and the output, a feedback IIR filter (14-2) and a switch (14-4) serially connected between the output and the adder, the feedforward FIR filter and the feedback IIR filter having filtering functions defined by the coefficients.

Frequency locking system using sound intermediate frequency (IF) carrier in a television signal

Abstract: A frequency controlled clock circuit for use in a television receiver utilizes a detected sound intermediate frequency (IF) signal for use in controlling a voltage controlled oscillator and thereby provide immunity from ghost signals in the transmitted video signal. A phase locked loop responds to phase errors detected from the voltage controlled oscillator and a reference signal from the sound IF signal to control the frequency of the voltage controlled oscillator.

High-performance JPEG image compression chip set for multimedia applications

Abstract: By its very nature, multimedia includes images, text and audio stored in digital format. Image compression is an enabling technology essential to overcoming two bottlenecks: cost of storage and bus speed limitation. Storing 10 seconds of high resolution RGB (640 X 480) motion video (30 frames/sec) requires 277 MBytes and a bus speed of 28 MBytes/sec (which cannot be handled by a standard bus). With high quality JPEG baseline compression the storage and bus requirements are reduced to 12 MBytes of storage and a bus speed of 1.2 MBytes/sec. Moreover, since consumer video and photography products (e.g., digital still video cameras, camcorders, TV) will increasingly use digital (and therefore compressed) images because of quality, accessibility, and the ease of adding features, compressed images may become the bridge between the multimedia computer and consumer products. The image compression challenge can be met by implementing the discrete cosine transform (DCT)-based image compression algorithm defined by the JPEG baseline standard. Using the JPEG baseline algorithm, an image can be compressed by a factor of about 24:1 without noticeable degradation in image quality. Because motion video is compressed frame by frame (or field by field), system cost is minimized (no frame or field memories and interframe operations are required) and each frame can be edited independently. Since JPEG is an international standard, the compressed files generated by this solution can be readily interchanged with other users and processed by standard software packages. This paper describes a multimedia image compression board utilizing Zoran's 040 JPEG Image Compression chip set. The board includes digitization, video decoding and compression. While the original video is sent to the display (`video in a window'), it is also compressed and transferred to the computer bus for storage. During playback, the system receives the compressed sequence from the bus and displays it on the screen.