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ADV601JS Datasheet(PDF) 3 Page - Analog Devices |
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ADV601JS Datasheet(HTML) 3 Page - Analog Devices |
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3 / 52 page  ADV601 –3– REV. 0 application. The sub-band coding architecture of the ADV601 provides a number of options to stretch compression perfor- mance. These options are outlined on in the Applying the ADV601 section. The DSP serial port interface (SPORT) enables performance of Bin Width calculations on a DSP instead of the host. The ADV601 transfers current video field statistics to the DSP and receives Bin Width data from the DSP as packet I/O through the DSP Inter- face. A generic fixed-point DSP (i.e., the ADSP-2105 low cost, fixed-point DSP) is more than adequate for these calculations. INTERNAL ARCHITECTURE The ADV601 is composed of nine blocks. Four of these blocks are interface blocks and five are processing blocks. The interface blocks are the Digital Video I/O Port, the Host I/O Port, exter- nal DRAM manager, and the DSP serial I/O Port. The process- ing blocks are the Wavelet Kernel, the On-Chip Transform Buffer, the Programmable Quantizer, the Run Length Coder, and the Huffman Coder. Digital Video I/O Port Provides a real-time uncompressed video interface to support a broad range of component digital video formats, including “D1.” Host I/O Port and FIFO Carries control, status, and compressed video to and from the host processor. A 512 position by 32-bit FIFO buffers the com- pressed video stream between the host and the Huffman Coder. DRAM Manager Performs all tasks related to writing, reading, and refreshing the external DRAM. The external host buffer DRAM is used for reordering and buffering quantizer input and output values. Serial Port (to Optional DSP) Supports, during encode only, communication of wavelet statis- tics between the Wavelet Kernel and the DSP and quantizer control information between the DSP and the Quantizer block. The user programmed compression ratio is also sent from the ADV601 host interface to the DSP automatically. Note that a host processor can be used to replace the DSP functionality in computer applications. Wavelet Kernel (Filters, Decimator, and Interpolator) Gathers statistics on a per field basis and includes a block of filters, interpolators, and decimators. The kernel calculates forward and backward bi-orthogonal, two-dimensional, sepa- rable wavelet transforms on horizontal scanned video data. This block uses the internal transform buffer when performing wave- let transforms calculated on an entire image’s data and so eliminates any need for extremely fast external memories in an ADV601-based design. On-Chip Transform Buffer Provides an internal set of SRAM for use by the wavelet trans- form kernel. Its function is to provide enough delay line storage to support calculation of separable two dimensional wavelet transforms for horizontally scanned images. Programmable Quantizer Quantizes wavelet coefficients. Quantize controls are calculated by the external DSP or host processor during encode operations and de-quantize controls are extracted from the compressed bit stream during decode. Each quantizer Bin Width is computed by the BW calculator software to maintain a constant com- pressed bit rate or constant quality bit rate. A Bin Width is a per block parameter the quantizer uses when determining the num- ber of bits to allocate to each block (sub-band). Run Length Coder Performs run length coding on zero data and models nonzero data, encoding or decoding for more efficient Huffman coding. This data coding is optimized across the sub-bands and varies depending on the block being coded. Huffman Coder Performs Huffman coder and decoder functions on quantized run-length coded coefficient values. The Huffman coder/de- coder uses three ROM-coded Huffman tables that provide ex- cellent performance for wavelet transformed video. GENERAL THEORY OF OPERATION The ADV601 processor’s compression algorithm is based on the bi-orthogonal (7, 9) wavelet transform, and implements field independent sub-band coding. Sub-band coders transform two- dimensional spatial video data into spatial frequency filtered sub-bands. The quantization and entropy encoding processes provide the ADV601’s data compression. The wavelet theory, on which the ADV601 is based, is a new mathematical apparatus first explicitly introduced by Morlet and Grossman in their works on geophysics during the mid 80s. This theory became very popular in theoretical physics and applied math. The late 80s and 90s have seen a dramatic growth in wavelet applications such as signal and image processing. For more on wavelet theory by Morlet and Grossman, see Decompo- sition of Hardy Functions into Square Integrable Wavelets of Con- stant Shape (journal citation listed in References section). ENCODE PATH DECODE PATH WAVELET KERNEL FILTER BANK ADAPTIVE QUANTIZER RUN LENGTH CODER & HUFFMAN CODER COMPRESSED DATA Figure 2. Encode and Decode Paths References For more information on the terms, techniques and underlying principles referred to in this data sheet, you may find the follow- ing reference texts useful. A reference text for general digital video principles is: Jack, K., Video Demystified: A Handbook for the Digital Engineer (High Text Publications, 1993) ISBN 1-878707-09-4 Three reference texts for wavelet transform background infor- mation are: Vetterli, M., Kovacevic, J., Wavelets And Sub-band Coding (Prentice Hall, 1995) ISBN 0-13-097080-8 Benedetto, J., Frazier, M., Wavelets: Mathematics And Applica- tions (CRC Press, 1994) ISBN 0-8493-8271-8 Grossman, A., Morlet, J., Decomposition of Hardy Functions into Square Integrable Wavelets of Constant Shape, Siam. J. Math. Anal., Vol. 15, No. 4, pp 723-736, 1984 |
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