pix_expand_h.h62

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  REVISION HISTORY                                                        *
*S      15-Oct-2000 Rewrote from scratch . . . . . . . . .  J. Zbiciak      *
*                                                                           *
*   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.                           *
* ========================================================================= *
        .sect ".opt_pix_expand"
        .global _pix_expand_asm

* ========================================================================= *
*   End of file:  pix_expand_h.h62                                          *
* ------------------------------------------------------------------------- *
*             Copyright (c) 2000 Texas Instruments, Incorporated.           *
*                            All Rights Reserved.                           *
* ========================================================================= *