img_mad_8x8.h

dm642函数库

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/*  TEXAS INSTRUMENTS, INC.                                                 */
/*                                                                          */
/*  IMGLIB  DSP Image/Video Processing Library                              */
/*                                                                          */
/*      Release:        Revision 1.04b                                      */
/*      CVS Revision:   1.16    Sun Sep 29 02:31:01 2002 (UTC)              */
/*      Snapshot date:  23-Oct-2003                                         */
/*                                                                          */
/*  This library contains proprietary intellectual property of Texas        */
/*  Instruments, Inc.  The library and its source code are protected by     */
/*  various copyrights, and portions may also be protected by patents or    */
/*  other legal protections.                                                */
/*                                                                          */
/*  This software is licensed for use with Texas Instruments TMS320         */
/*  family DSPs.  This license was provided to you prior to installing      */
/*  the software.  You may review this license by consulting the file       */
/*  TI_license.PDF which accompanies the files in this library.             */
/* ------------------------------------------------------------------------ */
/*          Copyright (C) 2003 Texas Instruments, Incorporated.             */
/*                          All Rights Reserved.                            */
/* ======================================================================== */
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/*  Assembler compatibility shim for assembling 4.30 and later code on      */
/*  tools prior to 4.30.                                                    */
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/*  End of assembler compatibility shim.                                    */
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/*  TEXAS INSTRUMENTS, INC.                                                 */
/*                                                                          */
/*  NAME                                                                    */
/*      IMG_mad_8x8 : Minimum absolute Difference                           */
/*                                                                          */
/*  REVISION DATE                                                           */
/*      15-Aug-2001                                                         */
/*                                                                          */
/*  USAGE                                                                   */
/*                                                                          */
/*      This routine is C-callable and can be called as:                    */
/*                                                                          */
/*      void IMG_mad_8x8                                                    */
/*      (                                                                   */
/*          const unsigned char *ref_data,  // Ref. image to search //      */
/*          const unsigned char *src_data,  // Source 8x8 block     //      */
/*          int                 pitch,      // Width of ref image   //      */
/*          int sx, int sy,                 // Search window size   //      */
/*          unsigned int        *match      // Result               //      */
/*      );                                                                  */
/*                                                                          */
/*      The reference image is an image of width 'pitch'.  The IMG_mad_8x8  */
/*      routine searches a (sx,sy) window within the image.                 */
/*                                                                          */
/*      The source image is an 8x8 block of pixels which contain the        */
/*      image block that is being searched for.                             */
/*                                                                          */
/*      The match[] array is where the best match location and MAD value    */
/*      for the best match are stored.  The best match position and its     */
/*      absolute difference are returned in match, packed as follows:       */
/*                                                                          */
/*                     31             16 15             0                   */
/*                     +----------------+----------------+                  */
/*          match[0]:  |    X offset    |    Y offset    |                  */
/*                     +----------------+----------------+                  */
/*                                                                          */
/*                     31                               0                   */
/*                     +---------------------------------+                  */
/*          match[1]:  |   Sum of absolute differences   |                  */
/*                     +---------------------------------+                  */
/*                                                                          */
/*  DESCRIPTION                                                             */
/*      This routine locates the position in a reference image which        */
/*      most closely matches an 8x8 block from a source image, using        */
/*      the Minimum Absolute Difference metric.  Searches over a range      */
/*      that is 'sx' pixels wide and 'sy' pixels tall within a reference    */
/*      image that is 'pitch' pixels wide.                                  */
/*                                                                          */
/*      The search is performed in top-to-bottom, left-to-right order,      */
/*      with the earliest match taking precedence in the case of ties.      */
/*                                                                          */
/*      The match location as well as the Minimum Absolute Difference       */
/*      metric for the match are returned in the 'match' array.             */
/*      The first element contains the packed horizontal and vertical       */
/*      coordinates of the match, with the X coordinate in the upper        */
/*      halfword and the Y coordinate in the lower halfword.  The           */
/*      second element contains the MAD value for this match location.      */
/*                                                                          */
/*  TECHNIQUES                                                              */
/*      The inner loops that perform the 8x8 mads are completely            */
/*      unrolled and the outer two loops are collpaesd together. In         */
/*      addition all source image data is pre-loaded into registers.        */
/*                                                                          */
/*      The data required for any one row is brought in using               */
/*      non-aligned loads. SUBABS4 and DOTPU4 are used together to do       */
/*      the MAD computation.                                                */
/*                                                                          */
/*      To save instructions and fit within an 8 cycle loop, the            */
/*      precise location of a given match is not stored.  Rather,           */
/*      the loop iteration that it was encountered on is stored.            */
/*      A short divide loop after the search loop converts this             */
/*      value into X and Y coordinates for the location.                    */
/*                                                                          */
/*  ASSUMPTIONS                                                             */