?? img_ycbcr422p_rgb565.h
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/* the 219-level range of Y'. Expected ranges are [16..235] for */
/* Y' and [16..240] for Cb and Cr. */
/* */
/* coeff[] = { 0x2000, 0x2BDD, -0x0AC5, -0x1658, 0x3770 }; */
/* */
/* [ 1.0000 0.0000 1.3707 ] [ Y' - 16 ] [ R'] */
/* [ 1.0000 -0.3365 -0.6982 ] * [ Cb - 128 ] = [ G'] */
/* [ 1.0000 1.7324 0.0000 ] [ Cr - 128 ] [ B'] */
/* */
/* 2. Y'CbCr -> RGB conversion with the 219-level range of Y' */
/* expanded to fill the full RGB dynamic range. (The matrix */
/* has been scaled by 255/219.) Expected ranges are [16..235] */
/* for Y' and [16..240] for Cb and Cr. */
/* */
/* coeff[] = { 0x2543, 0x3313, -0x0C8A, -0x1A04, 0x408D }; */
/* */
/* [ 1.1644 0.0000 1.5960 ] [ Y' - 16 ] [ R'] */
/* [ 1.1644 -0.3918 -0.8130 ] * [ Cb - 128 ] = [ G'] */
/* [ 1.1644 2.0172 0.0000 ] [ Cr - 128 ] [ B'] */
/* */
/* 3. Y'CbCr -> BGR conversion with RGB levels that correspond to */
/* the 219-level range of Y'. This is equivalent to #1 above, */
/* except that the R, G, and B output order in the packed */
/* pixels is reversed. Note: The 'cr_data' and 'cb_data' */
/* input arguments must be exchanged for this example as */
/* indicated under USAGE above. */
/* */
/* coeff[] = { 0x2000, 0x3770, -0x1658, -0x0AC5, 0x2BDD }; */
/* */
/* [ 1.0000 0.0000 1.7324 ] [ Y' - 16 ] [ B'] */
/* [ 1.0000 -0.6982 -0.3365 ] * [ Cr - 128 ] = [ G'] */
/* [ 1.0000 1.3707 0.0000 ] [ Cb - 128 ] [ R'] */
/* */
/* 4. Y'CbCr -> BGR conversion with the 219-level range of Y' */
/* expanded to fill the full RGB dynamic range. This is */
/* equivalent to #2 above, except that the R, G, and B output */
/* order in the packed pixels is reversed. Note: The */
/* 'cr_data' and 'cb_data' input arguments must be exchanged */
/* for this example as indicated under USAGE above. */
/* */
/* coeff[] = { 0x2000, 0x408D, -0x1A04, -0x0C8A, 0x3313 }; */
/* */
/* [ 1.0000 0.0000 2.0172 ] [ Y' - 16 ] [ B'] */
/* [ 1.0000 -0.8130 -0.3918 ] * [ Cr - 128 ] = [ G'] */
/* [ 1.0000 1.5960 0.0000 ] [ Cb - 128 ] [ R'] */
/* */
/* Other scalings of the color differences (B'-Y') and (R'-Y') */
/* (sometimes incorrectly referred to as U and V) are supported, as */
/* long as the color differences are unsigned values centered around */
/* 128 rather than signed values centered around 0, as noted above. */
/* */
/* In addition to performing plain color-space conversion, color */
/* saturation can be adjusted by scaling coeff[1] through coeff[4]. */
/* Similarly, brightness can be adjusted by scaling coeff[0]. */
/* General hue adjustment can not be performed, however, due to the */
/* two zeros hard-coded in the matrix. */
/* */
/* TECHNIQUES */
/* Pixel replication is performed implicitly on chroma data to */
/* reduce the total number of multiplies required. The chroma */
/* portion of the matrix is calculated once for each Cb, Cr pair, */
/* and the result is added to both Y' samples. */
/* */
/* Matrix Multiplication is performed as a combination of MPY2s and */
/* DOTP2s. Saturation to 8bit values is performed using SPACKU4 */
/* which takes in 4 signed 16-bit values and saturates them to */
/* unsigned 8-bit values. The output of Matrix Multiplication would */
/* ideally be in a Q13 format. This however, cannot be fed directly */
/* to SPACKU4. */
/* */
/* This implies a shift left by 3 bits, which could be pretty */
/* expensive in terms of the number of shifts to be performed. Thus, */
/* to avoid being bottlenecked by so many shifts, the Y, Cr & Cb data */
/* are shifted left by 3 before multiplication. This is possible */
/* because they are 8-bit unsigned data. Due to this, the output of */
/* Matrix Multiplication is in a Q16 format, which can be directly */
/* fed to SPACKU4. */
/* */
/* Because the loop accesses four different arrays at three */
/* different strides, no memory accesses are allowed to parallelize */
/* in the loop. No bank conflicts occur, as a result. */
/* */
/* The epilog has been completely removed, while the prolog is left */
/* as is. However, some cycles of the prolog are performed using the */
/* kernel cycles to help reduce code-size. The setup code is merged */
/* along with the prolog for speed. */
/* */
/* ASSUMPTIONS */
/* The number of luma samples to be processed needs to be a multiple */
/* of 8. */
/* The input Y array needs to be double-word aligned. */
/* The input Cr and Cb arrays need to be word aligned */
/* The output image must be double-word aligned. */
/* */
/* NOTES */
/* No bank conflicts occur. */
/* */
/* Codesize is 952 bytes. */
/* */
/* Memory bank conflicts will not occurs since the 3 loads and two */
/* stores happen in different cycles of the loop */
/* */
/* The kernel requires 3 words of stack space. */
/* */
/* CYCLES */
/* 12 * num_pixels/8 + 50 */
/* */
/* CODESIZE */
/* 952 bytes */
/* */
/* SOURCE */
/* Poynton, Charles et al. "The Color FAQ," 1999. */
/* http://home.inforamp.net/~poynton/ColorFAQ.html */
/* ------------------------------------------------------------------------ */
/* Copyright (c) 2002 Texas Instruments, Incorporated. */
/* All Rights Reserved. */
/* ======================================================================== */
#ifndef IMG_YCBCR422P_RGB565_H_
#define IMG_YCBCR422P_RGB565_H_ 1
void IMG_ycbcr422p_rgb565
(
const short coeff[5], /* Matrix coefficients. */
const unsigned char *y_data, /* Luminence data (Y') */
const unsigned char *cb_data, /* Blue color-diff (B'-Y') */
const unsigned char *cr_data, /* Red color-diff (R'-Y') */
unsigned short
*restrict rgb_data, /* RGB 5:6:5 packed pixel out. */
unsigned num_pixels /* # of luma pixels to process */
);
#endif
/* ======================================================================== */
/* End of file: img_ycbcr422p_rgb565.h */
/* ------------------------------------------------------------------------ */
/* Copyright (c) 2002 Texas Instruments, Incorporated. */
/* All Rights Reserved. */
/* ======================================================================== */
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