Query on Black bands seen with ADV7281

Hi,

 By default, the ADV728x will output in 'ITU BT656-3' timing format .If the receiver chip is expecting 'ITU BT656-4' format then this can result in 10 more dark lines appearing at the top of the screen in NTSC mode. 

This is because 'ITU BT656-3' format has 10 more lines of vertical blanking than 'ITU BT656-4' format. 

Also if you have not tried '0x04[7]' bit, then program the ADV728x to output in 'ITU BT656-4' format (Set User Map, register 0x04 bit[7] to 1).

Kindly check ADV728x hardware manual for more information: http://www.analog.com/media/en/technical-documentation/user-guides/ADV7280_7281_7282_7283_UG-637.pdf

Thanks,

Poornima

Hello Poornima,

Thank you for the quick response.

Yes, we have already attempted the above suggestion in parallel setting register 0x04 bit[7] to 1. This adjustment has helped reduce the number of black lines at the top from 22 to 2. However, the black lines at the bottom and on the right side remain unchanged.

Additionally, we have the following queries:

1) How can we eliminate the horizontal black bands at the top and bottom?
  a. If removal is not possible, is there a way to shift the black band entirely to the bottom?
2) How can we completely remove the vertical black band on the right side?

Hi,

  Please try with HS/VS position control registers for image shipment and for more details refer Page '77,78' at https://www.analog.com/media/en/technical-documentation/user-guides/adv7280_7281_7282_7283_ug-637.pdf

Also, Please make sure with crystal clock (i.e) Make sure you are providing correct XTAL 28.6363.

Thanks,

Poornima

Hello,

Please find the response in-line:

PoornimaSubramani said:

  Please try with HS/VS position control registers for image shipment and for more details refer Page '77,78' at https://www.analog.com/media/en/technical-documentation/user-guides/adv7280_7281_7282_7283_ug-637.pdf

The current values of the HS Position Control registers are as follows:

Reg 0x34 = 0x00
Reg 0x35 = 0x02
Reg 0x36 = 0x00
To shift the image 4 pixels to the RIGHT (to eliminate the black 4 pixels on the right side):

HSB_new = 2 + 4 = 6 → 0x006
HSE_new = 0 + 4 = 4 → 0x004
Updated register values:

Reg 0x34 = 0x00
Reg 0x35 = 0x06
Reg 0x36 = 0x04
However, modifying these registers did not result in any visible change in the video output.
According to the datasheet, the HS Position Control registers are used to configure the output HSYNC. The ADV7281 variant being used does not include Sync Output Pins, which might explain the lack of effect.

Do we have any other options to eliminate the black lines ?

PoornimaSubramani said:

Also, Please make sure with crystal clock (i.e) Make sure you are providing correct XTAL 28.6363.

Yes, 28,63636MHz crystal is connected.

Hi,

  I believe the camera is trying to generate some sort of "Letter Box" format so that might be the reason for black band/lines.

  Please try configuring 'letterbox' related registers at  https://www.analog.com/media/en/technical-documentation/user-guides/adv7280_7281_7282_7283_ug-637.pdf

  Also kindly refer here  ADV7181C Letterbox detection issue 

Thanks,

Poornima

Hello Poornima,

Thanks for the reply. PFB the response in-line:

kjrajendraprasad said:

Reg 0x34 = 0x00
Reg 0x35 = 0x06
Reg 0x36 = 0x04
However, modifying these registers did not result in any visible change in the video output.
According to the datasheet, the HS Position Control registers are used to configure the output HSYNC. The ADV7281 variant being used does not include Sync Output Pins, which might explain the lack of effect.

Do we have any other options to eliminate the black lines ?

Is this assumption correct? Can we confirm whether the HS Position Control registers only affect the Sync Output Pins (if available) or will they also modify the embedded video stream HS timing?

PoornimaSubramani said:

  I believe the camera is trying to generate some sort of "Letter Box" format so that might be the reason for black band/lines.

We have already connected the camera unit's output to an analog NTSC monitor, which displays the video stream without any black lines. According to the camera specifications, it outputs a 480i stream, suggesting that the black bars are not introduced by the video source.

PoornimaSubramani said:

  Please try configuring 'letterbox' related registers at  https://www.analog.com/media/en/technical-documentation/user-guides/adv7280_7281_7282_7283_ug-637.pdf

  Also kindly refer here  ADV7181C Letterbox detection issue 

Attached is the complete user sub-map register dump of the ADV7281 for the video streaming use case. The observed values for the letterbox data registers are as follows:

addr 0x0 data 0xe
addr 0x1 data 0xc8
addr 0x2 data 0x44
addr 0x3 data 0x4e
addr 0x4 data 0x57
addr 0x5 data 0x0
addr 0x6 data 0x2
addr 0x7 data 0x7f
addr 0x8 data 0x80
addr 0x9 data 0x80
addr 0xa data 0x0
addr 0xb data 0x0
addr 0xc data 0x36
addr 0xd data 0x7c
addr 0xe data 0x20
addr 0xf data 0x0
addr 0x10 data 0x5
addr 0x11 data 0x43
addr 0x12 data 0x0
addr 0x13 data 0x69
addr 0x14 data 0x10
addr 0x15 data 0x8
addr 0x16 data 0x40
addr 0x17 data 0x41
addr 0x18 data 0x93
addr 0x19 data 0xf1
addr 0x1a data 0x58
addr 0x1b data 0x1
addr 0x1c data 0xab
addr 0x1d data 0xc0
addr 0x1e data 0x16
addr 0x1f data 0x10
addr 0x20 data 0xe2
addr 0x21 data 0x51
addr 0x22 data 0x4b
addr 0x23 data 0xc4
addr 0x24 data 0x5
addr 0x25 data 0x0
addr 0x26 data 0x22
addr 0x27 data 0x58
addr 0x28 data 0xc
addr 0x29 data 0x38
addr 0x2a data 0x20
addr 0x2b data 0xe1
addr 0x2c data 0xae
addr 0x2d data 0xf5
addr 0x2e data 0xae
addr 0x2f data 0xf6
addr 0x30 data 0xf4
addr 0x31 data 0x2
addr 0x32 data 0x41
addr 0x33 data 0x84
addr 0x34 data 0x0
addr 0x35 data 0x2
addr 0x36 data 0x0
addr 0x37 data 0x81
addr 0x38 data 0x80
addr 0x39 data 0xc0
addr 0x3a data 0x0
addr 0x3b data 0x44
addr 0x3c data 0x58
addr 0x3d data 0x22
addr 0x3e data 0x64
addr 0x3f data 0xe4
addr 0x40 data 0x18
addr 0x41 data 0x0
addr 0x42 data 0x0
addr 0x43 data 0x0
addr 0x44 data 0x0
addr 0x45 data 0x0
addr 0x46 data 0x0
addr 0x47 data 0x0
addr 0x48 data 0x0
addr 0x49 data 0x6
addr 0x4a data 0x0
addr 0x4b data 0x0
addr 0x4c data 0x80
addr 0x4d data 0x0
addr 0x4e data 0x0
addr 0x4f data 0x0
addr 0x50 data 0x8
addr 0x51 data 0x20
addr 0x52 data 0x0
addr 0x53 data 0x0
addr 0x54 data 0x0
addr 0x55 data 0x0
addr 0x56 data 0x0
addr 0x57 data 0x0
addr 0x58 data 0x0
addr 0x59 data 0x0
addr 0x5a data 0x0
addr 0x5b data 0x0
addr 0x5c data 0x0
addr 0x5d data 0x0
addr 0x5e data 0x0
addr 0x5f data 0x0
addr 0x60 data 0x88
addr 0x61 data 0x10
addr 0x62 data 0x15
addr 0x63 data 0x6e
addr 0x64 data 0x0
addr 0x65 data 0x0
addr 0x66 data 0x0
addr 0x67 data 0x0
addr 0x68 data 0x0
addr 0x69 data 0x0
addr 0x6a data 0x0
addr 0x6b data 0x0
addr 0x6c data 0x0
addr 0x6d data 0x0
addr 0x6e data 0x0
addr 0x6f data 0x0
addr 0x70 data 0x0
addr 0x71 data 0x0
addr 0x72 data 0x0
addr 0x73 data 0x0
addr 0x74 data 0x0
addr 0x75 data 0x0
addr 0x76 data 0x0
addr 0x77 data 0x0
addr 0x78 data 0x0
addr 0x79 data 0x0
addr 0x7a data 0x0
addr 0x7b data 0x0
addr 0x7c data 0x0
addr 0x7d data 0x0
addr 0x7e data 0x0
addr 0x7f data 0x0
addr 0x80 data 0x0
addr 0x81 data 0x0
addr 0x82 data 0x0
addr 0x83 data 0x0
addr 0x84 data 0x0
addr 0x85 data 0x0
addr 0x86 data 0x0
addr 0x87 data 0x0
addr 0x88 data 0x0
addr 0x89 data 0x0
addr 0x8a data 0x0
addr 0x8b data 0x0
addr 0x8c data 0x0
addr 0x8d data 0x0
addr 0x8e data 0x0
addr 0x8f data 0x0
addr 0x90 data 0x0
addr 0x91 data 0x0
addr 0x92 data 0x0
addr 0x93 data 0x0
addr 0x94 data 0x0
addr 0x95 data 0x0
addr 0x96 data 0x0
addr 0x97 data 0x0
addr 0x98 data 0x0
addr 0x99 data 0x0
addr 0x9a data 0x0
addr 0x9b data 0x0
addr 0x9c data 0x30
addr 0x9d data 0x0
addr 0x9e data 0x0
addr 0x9f data 0x0
addr 0xa0 data 0x0
addr 0xa1 data 0x0
addr 0xa2 data 0x0
addr 0xa3 data 0x0
addr 0xa4 data 0x0
addr 0xa5 data 0x0
addr 0xa6 data 0x0
addr 0xa7 data 0x0
addr 0xa8 data 0x0
addr 0xa9 data 0x0
addr 0xaa data 0x0
addr 0xab data 0x0
addr 0xac data 0x0
addr 0xad data 0x0
addr 0xae data 0x0
addr 0xaf data 0x0
addr 0xb0 data 0x0
addr 0xb1 data 0x0
addr 0xb2 data 0x0
addr 0xb3 data 0x0
addr 0xb4 data 0x0
addr 0xb5 data 0x0
addr 0xb6 data 0x0
addr 0xb7 data 0x0
addr 0xb8 data 0x0
addr 0xb9 data 0x0
addr 0xba data 0x0
addr 0xbb data 0x0
addr 0xbc data 0x0
addr 0xbd data 0x0
addr 0xbe data 0x0
addr 0xbf data 0x0
addr 0xc0 data 0x0
addr 0xc1 data 0x0
addr 0xc2 data 0x0
addr 0xc3 data 0x0
addr 0xc4 data 0x0
addr 0xc5 data 0x0
addr 0xc6 data 0x0
addr 0xc7 data 0x0
addr 0xc8 data 0x0
addr 0xc9 data 0x0
addr 0xca data 0x0
addr 0xcb data 0x0
addr 0xcc data 0x0
addr 0xcd data 0x0
addr 0xce data 0x0
addr 0xcf data 0x0
addr 0xd0 data 0x0
addr 0xd1 data 0x0
addr 0xd2 data 0x0
addr 0xd3 data 0x0
addr 0xd4 data 0x0
addr 0xd5 data 0x0
addr 0xd6 data 0x0
addr 0xd7 data 0x0
addr 0xd8 data 0x0
addr 0xd9 data 0x0
addr 0xda data 0x0
addr 0xdb data 0x0
addr 0xdc data 0x0
addr 0xdd data 0x0
addr 0xde data 0x0
addr 0xdf data 0x0
addr 0xe0 data 0x0
addr 0xe1 data 0x0
addr 0xe2 data 0x0
addr 0xe3 data 0x0
addr 0xe4 data 0x0
addr 0xe5 data 0x0
addr 0xe6 data 0x0
addr 0xe7 data 0x0
addr 0xe8 data 0x0
addr 0xe9 data 0x0
addr 0xea data 0x0
addr 0xeb data 0x0
addr 0xec data 0x0
addr 0xed data 0x0
addr 0xee data 0x0
addr 0xef data 0x0
addr 0xf0 data 0x0
addr 0xf1 data 0x0
addr 0xf2 data 0x0
addr 0xf3 data 0x0
addr 0xf4 data 0x0
addr 0xf5 data 0x0
addr 0xf6 data 0x0
addr 0xf7 data 0x0
addr 0xf8 data 0x0
addr 0xf9 data 0x0
addr 0xfa data 0x0
addr 0xfb data 0x0
addr 0xfc data 0x0
addr 0xfd data 0x0
addr 0xfe data 0x0
addr 0xff data 0x0

- LB_LCT (0x9B): 0x0  
- LB_LCM (0x9C): 0x30  
- LB_LCB (0x9D): 0x0  

Attempts to modify the Letterbox Control registers were made, but after successfully writing to the 0xDC and 0xDD registers, the values were not retained, as subsequent reads of the registers returned 0x00.

From the hardware manual, it appears that the letterbox feature only detects black lines in the incoming video. Can it also remove the black lines in the ADV7281 video output?

Hi,

  From the hardware manual, it appears that the letterbox feature only detects black lines in the incoming video. Can it also remove the black lines in the ADV7281 video output ?

    Yes, letterbox feature detects only black lines in the incoming video but it will not remove or add any black lines in the ADV728x output (It just passthrough the video).

 Also Please let us know, Have you verified the same issue with back to back connection/Direct Connection ( Source --> Sink) ?

Thanks,

Poornima

Hello Poornima,

I'm the team mate of the author.

We have verified the source by directly connecting it to a monitor (No ADV7281 involved). No black lines seen vertical or horizontal.

Its clear that ADV7281 is inserting the horizontal black line to be complaint to ITU-BT656 standard.

Our customer wants the horizontal black lines removed or make it symmetric.

In additional we still dint understand why the vertical black like is inserted by ADV7281.

Please support us!

Hi ,

    Could you please provide the detailed setup information?

Thanks,

Ebin

Hello Ebin

Thanks for the reply.

Currently we are using this External Monitor which is connected to the DVR Module

https://www.amazon.co.jp/Antion-4-3%E3%82%A4%E3%83%B3%E3%83%81%E3%83%A2%E3%83%8B%E3%82%BF%E3%83%BC-…

Thank You

Akash