TDA4VM: LDC H-Delta multiplication factor and Mesh values

Dinesh bharathi

Part Number: TDA4VM

Hi,

I am using the Matlab for generating the mesh from the spec file values.

h_delta = round((h_d-h_p) * 8);

v_delta = round((v_d-v_p) * 8);

1)I have a doubt on why we are having to use the multiplication factor of 8.
2) I understand the mesh represent the back mapping pixel values but the values doesn't match with the grid values. I.e The values extend from 1824 to -1824 when the frame size is only 1920 width. Or am assuming that these values inside the generated grid are back mapping pixel locations? The reason behind this question is i am trying to understand what these numbers actually mean.
Regards,
Dinesh

over 3 years ago

0 Gang Hua over 3 years ago

TI__Guru 60090 points

Hi Dinesh,

1) This "8" is required by H/W encoding of the LUT.

2) The meaning of numbers are exactly as in the 2 lines of code.

h_delta = round((h_d-h_p) * 8);
v_delta = round((v_d-v_p) * 8);

You understand that "(h_p, v_p)" and "(h_d, v_d)" are locations before and after back mapping.

0 Dinesh bharathi over 3 years ago in reply to Gang Hua

Intellectual 751 points

1) So I consider the HW details to be a black block and that black box requires multiples of 8 for the process, am i right? And it is going to be 8 only in all the cases is what i take away from here.

2) I do understand "(h_p, v_p)" and "(h_d, v_d)" but My doubt is when these numbers exceed 0 to 1920 . Or it is again something related to H/W. So these numbers in mesh.txt aren't exactly pointing to input to output is what I could assume at this point.

0 Gang Hua over 3 years ago in reply to Dinesh bharathi

TI__Guru 60090 points

Yes, the mesh LUT is just the H/W way of encoding your geometric mapping.

The range of the numbers in the LUT is 16-bit signed integers.
The definition of is clear from the code.

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TDA4VM: LDC H-Delta multiplication factor and Mesh values