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TDA3XEVM: Vision SDK 3.2/LDC: Where can I find Informations about the structure of a Mesh Table, when I want to calculate my own one?

Part Number: TDA3XEVM


where can I find Informations about the structure of a Mesh Table, when I want to calculate my own one?

I want to be able to setup my own ways on how to e.g. distorte an image and I want to be able to understand, what has gone wrong, when it does not work well.



  • Hi Guenter,

    I have forwarded your question to an expert for comment.

  • The description of LDC mesh table is in TDA3x TRM.

    The logical content of the table has 2 columns of 16-bit singed integers (S16Q3). The first column is the horizontal offset and the second vertical offset of a pixel. The offsets are relative to the pixel location starting from 0 with 1/8 pixel precision. The table is typically down-sampled by 8x8 (m=3) or 16x16 (m=4).

    To create your own table, you need to define your geometric mapping first. The mapping is from each output pixel at location (h_p, v_p) to its location (h_d, v_d) in input image. The table is (h_d - h_p, v_d - v_p) in some integer format.

    I have some example matlab/octave code below to create a table from a fisheye lens spec file (text file with 2 columns; 1st is the angle of view in degree and 2nd image height in mm). This example takes care of the table down-sampling and integer format. "gen_lut" is the function you need to call with the spec file name, sensor pixel pitch in mm, focal length in mm, input image width (W) and height (H), input image center (hc and vc), a scaling factor (s), and table down-sampling factor (m). The output is a text file "mesh.txt".

    Once you get your table as above, you can try it out in the DCC ISP tuning tool (which also give you good parameters for other LDC registers). If the table works as expected in the tuning tool, you can convert the table into vision sdk binary format using "apps/tools/LDC_mesh_table_convert/" in vision sdk.