Changing IPU Color Space Conversion parameters

Document created by rogeriopimentel Employee on Oct 14, 2015Last modified by ebiz_ws_prod on Dec 13, 2017
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Inside IPU there are two block where color space conversion can be made: IC (Image Converter) and DP (Display processor).

On Linux, the CSC parameters are located at IPU (IC and DP) drivers, linux/drivers/mxc/ipu3 folder.

 

All negative coefficients are represented using two's complement.

 

Linux Image Converter driver:

 

The parameters are set on function _init_csc:

 

http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/tree/drivers/mxc/ipu3/ipu_ic.c?h=imx_3.14.28_1.0.0_ga

 

static void _init_csc(struct ipu_soc *ipu, uint8_t ic_task, ipu_color_space_t in_format,
ipu_color_space_t out_format, int csc_index)
{
/*
* Y = 0.257 * R + 0.504 * G + 0.098 * B + 16;
* U = -0.148 * R - 0.291 * G + 0.439 * B + 128;
* V = 0.439 * R - 0.368 * G - 0.071 * B + 128;
*/

static const uint32_t rgb2ycbcr_coeff[4][3] = {
{0x0042, 0x0081, 0x0019},
{0x01DA, 0x01B6, 0x0070},
{0x0070, 0x01A2, 0x01EE},
{0x0040, 0x0200, 0x0200}, /* A0, A1, A2 */
};

/* transparent RGB->RGB matrix for combining
*/

static const uint32_t rgb2rgb_coeff[4][3] = {
{0x0080, 0x0000, 0x0000},
{0x0000, 0x0080, 0x0000},
{0x0000, 0x0000, 0x0080},
{0x0000, 0x0000, 0x0000}, /* A0, A1, A2 */
};

/* R = (1.164 * (Y - 16)) + (1.596 * (Cr - 128));
  G = (1.164 * (Y - 16)) - (0.392 * (Cb - 128)) - (0.813 * (Cr - 128));
  B = (1.164 * (Y - 16)) + (2.017 * (Cb - 128); */

static const uint32_t ycbcr2rgb_coeff[4][3] = {
{149, 0, 204},
{149, 462, 408},
{149, 255, 0},
{8192 - 446, 266, 8192 - 554}, /* A0, A1, A2 */
};

 

 

Linux Display Processor driver:

 

The parameters are set on constants (rgb2ycbcr_coeff and ycbcr2rgb_coeff):

 

http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/tree/drivers/mxc/ipu3/ipu_disp.c?h=imx_3.14.28_1.0.0_ga

 

/* Y = R * 1.200 + G * 2.343 + B * .453 + 0.250;
  U = R * -.672 + G * -1.328 + B * 2.000 + 512.250.;
  V = R * 2.000 + G * -1.672 + B * -.328 + 512.250.;*/

static const int rgb2ycbcr_coeff[5][3] = {
{0x4D, 0x96, 0x1D},
{-0x2B, -0x55, 0x80},
{0x80, -0x6B, -0x15},
{0x0000, 0x0200, 0x0200}, /* B0, B1, B2 */
{0x2, 0x2, 0x2}, /* S0, S1, S2 */
};

/* R = (1.164 * (Y - 16)) + (1.596 * (Cr - 128));
  G = (1.164 * (Y - 16)) - (0.392 * (Cb - 128)) - (0.813 * (Cr - 128));
  B = (1.164 * (Y - 16)) + (2.017 * (Cb - 128); */

static const int ycbcr2rgb_coeff[5][3] = {
{0x095, 0x000, 0x0CC},
{0x095, 0x3CE, 0x398},
{0x095, 0x0FF, 0x000},
{0x3E42, 0x010A, 0x3DD6}, /*B0,B1,B2 */
{0x1, 0x1, 0x1}, /*S0,S1,S2 */
};

Original Attachment has been moved to: csc_ex3.c.zip

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