📄 img_quantize.h64
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;* ======================================================================== *;
;* TEXAS INSTRUMENTS, INC. *;
;* *;
;* IMGLIB DSP Image/Video Processing Library *;
;* *;
;* Release: Revision 1.04b *;
;* CVS Revision: 1.10 Sun Sep 29 03:32:28 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. *;
;* ======================================================================== *;
;* ======================================================================== *;
;* Assembler compatibility shim for assembling 4.30 and later code on *;
;* tools prior to 4.30. *;
;* ======================================================================== *;
;* ======================================================================== *;
;* End of assembler compatibility shim. *;
;* ======================================================================== *;
* ========================================================================= *
* *
* TEXAS INSTRUMENTS, INC. *
* *
* NAME *
* IMG_quantize -- Matrix Quantization w/ Rounding, Little Endian *
* *
* REVISION DATE *
* 04-Feb-2000 *
* *
* USAGE *
* This routine is C callable, and has the following C prototype: *
* *
* void IMG_quantize *
* ( *
* short *data, /* Data to be quantized. */ *
* unsigned short num_blks, /* Number of blocks to process. */ *
* unsigned short blk_size, /* Block size (multiple of 16). */ *
* const short *recip_tbl, /* Quant. values (reciprocals). */ *
* int q_pt /* Q-point of Quant values. */ *
* ) *
* *
* The number of blocks, num_blks, may be zero. The block *
* size (number of elements in each block) must be at least 32, *
* and a multiple of 16. The Q-point, q_pt, controls rounding and *
* final truncation; it must be in the range from 0 <= q_pt <= 31. *
* *
* Both input arrays, data[] and recip_tbl[], must be double-word *
* aligned. The data[] array must be 'num_blks * blk_size' elements, *
* and the recip_tbl[] array must be 'blk_size' elements. *
* *
* DESCRIPTION *
* The function IMG_quantize() quantizes matrices by multiplying their *
* contents with a second matrix that contains reciprocals of the *
* quantization terms. This step corresponds to the quantization *
* that is performed in 2-D DCT-based compression techniques, *
* although IMG_quantize() may be used on any signed 16-bit data using *
* signed 16-bit quantization terms. *
* *
* IMG_quantize() multiplies the contents of the quantization matrix *
* with the data being quantized. Therefore, it may be used for *
* inverse quantization as well, by setting the Q-point *
* appropriately. *
* *
* The assembly code requires 26 + (blk_size/16) * num_blks * 8 *
* cycles to execute, including function call overhead. This code *
* does not explicitly disable interrupts. On entry to the function, *
* interrupts are masked by branch delay slots for a maximum of 16 *
* cycles. *
* *
* The following C code describes the general implementation of *
* IMG_quantize(). *
* *
* void IMG_quantize *
* ( *
* short *data, /* Data to be quantized. */ *
* unsigned short num_blks, /* Number of 64-element blocks. */ *
* unsigned short blk_size, /* Block size (multiple of 16). */ *
* const short *recip_tbl, /* Quant. values (reciprocals). */ *
* int q_pt /* Q-point of Quant values. */ *
* ) *
* { *
* short recip; *
* int i, j, k, quot, round; *
* *
* round = q_pt ? 1 << (q_pt - 1) : 0; *
* *
* for (i = 0; i < blk_size; i++) *
* { *
* recip = recip_tbl[i]; *
* k = i; *
* for (j = 0; j < num_blks; j++) *
* { *
* quot = data[k] * recip + round; *
* data[k] = quot >> q_pt; *
* k += blk_size; *
* } *
* } *
* } *
* *
* The above C code is a general implementation without *
* restrictions. The assembly code has restrictions, as noted above. *
* *
* TECHNIQUES *
* The outer loop is unrolled 16 times to allow greater amounts *
* of work to be performed in the inner loop. The resulting loop- *
* nest was then collapsed and pipelined as a single loop, since *
* the code is not bottlenecked on bandwidth. *
* *
* Reciprocals and data terms are loaded in groups of four using *
* double-word loads, making best use of the available memory *
* bandwidth. *
* *
* SSHVR is used in the M-unit to avoid an S-unit bottleneck. *
* *
* Twin stack pointers have been used to speed up stack accesses. *
* *
* ASSUMPTIONS *
* The recip_tbl[] and data[] must be double-word aligned. *
* The block size, blk_size, must be a multiple of 16 and at least 32. *
* The number of blocks, num_blks, may be 0. *
* The Q-point, q_pt, must be in the range 0 <= q_pt <= 31. *
* *
* MEMORY NOTE *
* No bank conflicts occur, regardless of the relative orientation *
* of recip_tbl[] and data[]. *
* *
* A total of 6 words of stack frame are used for saving the *
* Save-On-Entry registers. *
* *
* NOTES *
* This code is fully interruptible, with a maximum interrupt latency *
* due to branch delay slots of 16. *
* *
* Input arrays must be double-word-aligned for correct operation. *
* *
* No checking is performed on the input arguments for correctness. *
* *
* CYCLES *
* cycles = 26 + (blk_size/16) * num_blks * 8 *
* *
* For blk_size = 64 and num_blks = 8, cycles = 282. *
* For blk_size = 256 and num_blks = 24, cycles = 3098. *
* *
* CODESIZE *
* 580 bytes *
* *
* SOURCE *
* n/a *
* *
* ------------------------------------------------------------------------- *
* Copyright (c) 2003 Texas Instruments, Incorporated. *
* All Rights Reserved. *
* ========================================================================= *
.global _IMG_quantize
* ========================================================================= *
* End of file: img_quantize.h64 *
* ------------------------------------------------------------------------- *
* Copyright (c) 2003 Texas Instruments, Incorporated. *
* All Rights Reserved. *
* ========================================================================= *
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