pix_expand_h.h

基于DM642平台的视频缩小放大功能 程序源代码

/* ======================================================================== */
/*  TEXAS INSTRUMENTS, INC.                                                 */
/*                                                                          */
/*  NAME                                                                    */
/*      pix_expand                                                          */
/*S                                                                        S*/
/*S REVISION HISTORY                                                       S*/
/*S     15-Oct-2000 Rewrote from scratch . . . . . . . . .  J. Zbiciak     S*/
/*                                                                          */
/*  USAGE                                                                   */
/*      This routine is C-callable and can be called as:                    */
/*                                                                          */
/*      void pix_expand_asm                                                 */
/*      (                                                                   */
/*          int n,                                    // # of elements //   */
/*          const unsigned char *restrict in_data,    // Input data    //   */
/*          short               *restrict out_data    // Output data   //   */
/*      )                                                                   */
/*                                                                          */
/*                                                                          */
/*  DESCRIPTION                                                             */
/*      The code takes an array of bytes and promotes them to half-words    */
/*      by zero-extension.                                                  */
/*                                                                          */
/*      This is the C equivalent of the assembly code, without              */
/*      restrictions.  The assembly code has restrictions, as noted below.  */
/*                                                                          */
/*      void pix_expand                                                     */
/*      (                                                                   */
/*          int n,                                                          */
/*          const unsigned char *restrict in_data,                          */
/*          short               *restrict out_data                          */
/*      )                                                                   */
/*      {                                                                   */
/*          int i;                                                          */
/*                                                                          */
/*          for (i = 0; i < n; i++)                                         */
/*              out_data[i] =  in_data[i];                                  */
/*      }                                                                   */
/*                                                                          */
/*  ASSUMPTIONS                                                             */
/*      Input and output arrays must be double-word (8-byte) aligned.       */
/*                                                                          */
/*      The input must be at least 16 elements long and contain a           */
/*      multiple of 16 elements.                                            */
/*                                                                          */
/*  NOTE                                                                    */
/*      Interrupts are masked during the entire duration of this            */
/*      function, as the entire function occurs within branch delay slots.  */
/*                                                                          */
/*  MEMORY NOTE                                                             */
/*      No bank conflicts occur.  This is a LITTLE ENDIAN implementation.   */
/*                                                                          */
/*  TECHNIQUES                                                              */
/*      The loop is unrolled 16 times, loading bytes with LDDW.  It uses    */
/*      UNPKHU4 and UNPKLU4 to unpack the data and store the results with   */
/*      STDW.                                                               */
/*                                                                          */
/*      To shave a few extra cycles from the function, the return branch    */
/*      is issued from within the kernel.                                   */
/*                                                                          */
/*                                                                          */
/*  CYCLES                                                                  */
/*      cycles = 3 * (n / 16) + 15.                                         */
/*      For n = 1072, cycles = 216.                                         */
/*                                                                          */
/*  CODESIZE                                                                */
/*      100 bytes.                                                          */
/*                                                                          */
/* ------------------------------------------------------------------------ */
/*            Copyright (c) 2000 Texas Instruments, Incorporated.           */
/*                           All Rights Reserved.                           */
/* ======================================================================== */
#ifndef _PIX_EXPAND_H_H
#define _PIX_EXPAND_H_H 1

void pix_expand_asm
(   
    int n,
    const unsigned char *restrict in_data,
    short               *restrict out_data
);

#endif
/* ======================================================================== */
/*  End of file:  pix_expand_h.h                                            */
/* ------------------------------------------------------------------------ */
/*            Copyright (c) 2000 Texas Instruments, Incorporated.           */
/*                           All Rights Reserved.                           */
/* ======================================================================== */