About PUx_DP_SCS_SYNC_0 register in i.MX6DQ.

[keitanagashima]

Dear All,

Hello.

Refer to DP_CSC_A8_SYNC [10 bit] in IPUx_DP_SCS_SYNC_0 register.

[Q1]

Could you tell me the plus/minus sign, integer part and decimal part in this bits?

9~10 --> plus/minus sign? Please explain the detail.

7~8 --> integer part?

0~6 --> decimal part?

The register detail description wasn't found.

[Q2]

Which is the right calculation round-up or round-off for 4th decimal place?

[Q3] (Confirming)

In case of DP_CSC_A8_SYNC = 0x3EB(0b1111101011), what is the result value at decimal value?

Best Regards,

Keita

[art]

A1. The Section 37.4.9.5 "Color Space Conversion unit - CSC" of the i.MX6DQ Reference Manual Rev.3 document says that each color space conversion A coefficient is "10-bit signed number with 8 fractional digits". So, the upper bit (bit 9) is a sign, next bit (bit 8) is the integer part and the bits 7 to 0 are the fractional part.

A2. The right decimal rounding rule is round to nearest.

A3. According to the Point 1 above, the coefficient value of 0x3EB is equal to -1.235 decimal number.

Have a great day,
Artur

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[keitanagashima]

Dear Artur,

Thank you for your quick reply.

Please check below question again.

>A1. The Section 37.4.9.5 "Color Space Conversion unit - CSC" of the i.MX6DQ Reference Manual Rev.3 document

> says that each color space conversion A coefficient is "10-bit signed number with 8 fractional digits".

> So, the upper bit (bit 9) is a sign, next bit (bit 8) is the integer part and the bits 7 to 0 are the fractional part.

I got the below information from Qiang Li. (https://community.freescale.com/docs/DOC-94019#start=100 )

For example,

0x96 --> 2.343

0x80 --> 2.000

These looks integer part (bit 8 & 9).

How do you think in this case?

=======

You can find it in drivers/mxc/ipu3/ipu_disp.c

/*     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 */

};

=======

Best Regards,

Keita

[art]

Looks strange. Let me investigate the case.

Artur

[keitanagashima]

Hi Artur,

Please follow-up the this question.

I can't close it.

Best Regards,

Keita

[art · Accepted solution]

For better understanding, refer to the following thread:

Changing IPU Color Space Conversion parameters

and follow the code, referenced there. Also, refer to the whole Section 37.4.9.5 "Color Space Conversion unit - CSC" of the i.MX6DQ Reference Manual Rev.3 document. The descriptions, given there, are correct. All coefficient numbers are represented using two's complement format.

Artur

[keitanagashima]

Hi Artur,

Did you find the right description?

Best Regards,

Keita

[keitanagashima]

Hi Artur,

Do you have any update?

When can you answer to me?

Best Regards,

Keita

[keitanagashima]

Hi Artur,

Do you have any update?

Best Regards,

Keita

[keitanagashima]

Hi Artur,

This register looks below.

bit 9--> plus/minus sign

bit [6~8] --> integer part

bit [0~5] --> decimal part

So, the description of "10-bit signed number with 8 fractional digits" looks typo.

Please check again.

Best Regards,

Keita