TDA4VM: Problem of LDC Module

ZHIJIE PAN

Part Number: TDA4VM

Hello all experts,

For my case, I want to use LDC module to correct the image with barrel distortion by using distortion parameters (Radial Distortion and Tangential Distortion) and intrinsic matrix.

Up to now, I have reviewed some relevant LDC issues in the forums and have learnt that I need to generate a Mesh LUT to implement the LDC. But all the issues are about fish-eye camera and Bird view.

Question:

So I am wondering,how can I generate a Mesh LUT for a wide-angle camera, not for a fish-eye camera? Or is there another way to correct the image with barrel distortion in TDA4?

Best regards.

over 3 years ago

+1 Gang Hua over 3 years ago

TI__Guru 59740 points

Hi Zhijie,

There is no difference between fisheye distortion and the radial distortion of a wide-angle lens.
Simple de-centering distortion may be accounted by adding another step of 3D rotation/shift after radial mapping as in the TDA4 LDC FAQ.
So, you may start with correcting the radial distortion first following the FAQ to get everything working in your system and then add the tangential correction.

On the other side, if you have all the lens parameters available and are able to calculate the input image coordinates "x,y" (distorted) from output image coordinates "u,v" (corrected), then you may generate the LUT by replacing the "u,v"-->"x,y" mapping in FAQ code with your own code.

As long as you have the correct LUT format, size, and row alignment padding, your LUT shall work with TDA4 LDC.

Best,
Gang

0 ZHIJIE PAN over 3 years ago in reply to Gang Hua

Prodigy 90 points

Hi Gang,

Thanks for replying. By the way, can you post me a download link of the DCC ISP tunning tool and convert.sh file that you mentioned in the FAQ? I can't find it in my system.

Best regards.

0 Mayank Mangla over 3 years ago in reply to ZHIJIE PAN

TI__Mastermind 24525 points

Hello Zhijie,

Tuning tool can be downloaded from https://www.ti.com/securesoftware/docs/autopagepreview.tsp?opnId=16092

You will need to login using your myTI account and request access.

Regards,

Mayank

0 ZHIJIE PAN over 3 years ago in reply to Mayank Mangla

Prodigy 90 points

Hi Mayank,

The download page shows that There Was An Error Processing Your Request. How can I deal with this?

Best,

Zhijie

0 Gang Hua over 3 years ago in reply to ZHIJIE PAN

TI__Guru 59740 points

Hi Zhijie,

There is no "convert.sh" for TDA4.

Please follow this FAQ:

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1058565/faq-tda4vm-how-to-create-a-ldc-mesh-lut-for-fisheye-distortion-correction-on-tda4?tisearch=e2e-sitesearch&keymatch=TDA4%20LDC%20faq#

Best,
Gang

0 ZHIJIE PAN over 3 years ago in reply to Gang Hua

Prodigy 90 points

Hi Gang,

Thanks for your kind instruction. If I have further questions, I will contact you soon.

But the above download link of tuning tool may be not accessed for me. If it is possible, please offer me another avaliable one.

Best regards.

0 Gang Hua over 3 years ago in reply to ZHIJIE PAN

TI__Guru 59740 points

Hi Zhijie,

>> You will need to login using your myTI account and request access.

The link shall be good.
Once your request is approved, you shall be able to access.
Please contact your local TI support if you have any issue with your myTI account.

Best,
Gang

0 ZHIJIE PAN over 3 years ago in reply to Gang Hua

Prodigy 90 points

Hi gang,

Now, I have some further questions.

First, in the Matlab code, there is one parameter called S Mesh Coverage. What does it mean?

And in the step, h_delta = round((h_d - h_p) * 8); v_delta = round((v_d - v_p) * 8); Why does it need to be multiplied by 8?

There is another question about one parameter of tivxVpacLdcNode. In the node, one parameter is called region_prms, which contains block width,height and pixel pad. What does this parameter mean? How should I set this parameter? In other words, how does this parameter effect the output image?

In addition, my local TI support has some problems that cannot offer me the tuning tool... If I try to generate LUT in right format and verify it by my own, can you give some ideas and procedure?

Thanks a lot.

Best,

Zhijie

0 Gang Hua over 3 years ago in reply to ZHIJIE PAN

TI__Guru 59740 points

1. S is a factor for controlling the size of the output view.

2. 8 is required by HW for encoding the offsets.

3. You may ignore the region parameters. It is about performance optimization. Please refer to TDA4 TRM if you need more details.

4. Please follow the FAQ above. It has all the information you need.

0 ZHIJIE PAN over 3 years ago in reply to Gang Hua

Prodigy 90 points

Hi Gang,

Thanks for replying.

Now my problem is although I can use the Matlab to generate the LUT in integer, due to lack of tuning tool, I have to transform the LUT result to uint16 binary manually.

So I review the header file LDC_LUT_1920_1080.h of the demo app_single_cam. But I find the header file is in uint8 form, could you please tell the physical meaning of each uint8 number?

{ \
0xba,0x06,0xe1,0x12,0xb7,0x06,0xc5,0x12,...

For example, uint8 to uint16 :0xba, 0x06->0x06ba(1722) 0xe1,0x12->0x12e1(4833).

Is it right? Which one is x or y offset? And why is the number greater than 1920?

If I put lut as a header file, do I need to transform it to uint8 rather than uint16, or uint16 is also ok?

Bests,Zhijie

0 Gang Hua over 3 years ago in reply to ZHIJIE PAN

TI__Guru 59740 points

Hi Zhijie,

Please take a look at the example in step 4 of the FAQ: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1058565/faq-tda4vm-how-to-create-a-ldc-mesh-lut-for-fisheye-distortion-correction-on-tda4?tisearch=e2e-sitesearch&keymatch=TDA4%20LDC%20faq

>> test_mesh_lut.txt

>> This H/W version of the mesh table "test_mesht_lut.txt" is in 32-bit words with little endian encoding and each row of the mesh table must be 16-byte aligned.
>> For example, the first row in "mesh.txt" above is "1818 (0x71a), 1341 (0x53d)", and the corresponding 32-bit binary word is "0x53d, 0x71a" in >>"test_mesh_lut.txt".
>> At the end of each row in "test_mesh_lut.txt", you can find the padding of six "0x0000" so that each row is 336 bytes (336=16x21).

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TDA4VM: Problem of LDC Module