ADV7280-M with CVBS Analog - Deinterlacing Issue

Question

Hi, 
 We are converting a CVBS NTSC-M video stream to CSI-2 with ADV7280-M having I2P enabled. The converted image is having some de-interlacing issues. The images are attached here with. Looks like even the color bars have similar issue. Our settings are below: 
 adv7180_write(state, 0x0F, 0x80); //chip reset msleep(50); adv7180_write(state, 0x0F, 0x00); //Exit Power Down Mode adv7180_write(state, 0xFE, 0x88); //Set CSI Map Address adv7180_write(state, 0xFD, 0x84); //Set VPP Map Address 
 adv7180_write(state, 0x00, 0x00); //INSEL = CVBS in on Ain 1 adv7180_write(state, 0x0E, 0x80); //ADI Required Write adv7180_write(state, 0x9C, 0x00); //ADI Required Write adv7180_write(state, 0x9C, 0xFF); //ADI Required Write adv7180_write(state, 0x0E, 0x00); //Enter User Sub Map adv7180_write(state, 0x03, 0x4E); //ADI Required Write adv7180_write(state, 0x04, 0x57); //Power-up INTRQ pad adv7180_write(state, 0x13, 0x00); //Enable INTRQ output driver adv7180_write(state, 0x17, 0x41); //select SH1 adv7180_write(state, 0x1D, 0xC0); //Tri-S LLC output driver adv7180_write(state, 0x52, 0xCD); //ADI Required Write adv7180_write(state, 0x80, 0x51); //ADI Required Write adv7180_write(state, 0x81, 0x51); //ADI Required Write adv7180_write(state, 0x82, 0x68); //ADI Required Write 
 adv7180_write(state, 0x38, 0x24); //NTSC comb control Tried with and without this adv7180_write(state, 0x6A, 0x03); //Output Sync Select 1 adv7180_write(state, 0x6B, 0x01); //Output Sync Select 2 
 adv7180_vpp_write(state, 0xA3, 0x00); //ADI Required Write adv7180_vpp_write(state, 0x5B, 0x00); //Advanced Timing Enabled adv7180_vpp_write(state, 0x55, 0x80); //Enable I2P 
 //enable fast switch adv7180_write(state, 0x0E, 0x00); //ADI Required Writes adv7180_write(state, 0x0E, 0x40); //Select User Sub Map 2 adv7180_write(state, 0xE0, 0x01); //Select fast Switching Mode. Tried with and without this adv7180_write(state, 0x0E, 0x00); //Select User Map 
 adv7180_csi_write(state, 0x01, 0x20); //ADI Required Write adv7180_csi_write(state, 0x02, 0x28); //ADI Required Write adv7180_csi_write(state, 0x03, 0x38); //ADI Required Write adv7180_csi_write(state, 0x04, 0x30); //ADI Required Write adv7180_csi_write(state, 0x05, 0x30); //ADI Required Write adv7180_csi_write(state, 0x06, 0x80); //ADI Required Write adv7180_csi_write(state, 0x07, 0x70); //ADI Required Write adv7180_csi_write(state, 0x08, 0x50); //ADI Required Write 
 adv7180_csi_write(state, 0xDE, 0x02); //Power up D-PHY adv7180_csi_write(state, 0xD2, 0xF7); //ADI Required Write adv7180_csi_write(state, 0xD8, 0x65); //ADI Required Write adv7180_csi_write(state, 0xE0, 0x09); //ADI Required Write adv7180_csi_write(state, 0x2C, 0x00); //ADI Required Write adv7180_csi_write(state, 0x1D, 0x80); //ADI Required Write adv7180_csi_write(state, 0x00, 0x00); //Power up CSI Block 
 Enabling/Disabling Fast switch mode is not helping either. 
 Are we missing some thing? Is it really de-interlacing issue (considering the color bars are also affected)? 
 Your help will be highly appreciated.

PoornimaSubramani · Accepted Answer

Hi, 
 Please let us know ,whether this issue observing even in PAL format and also other interface like Y/C, and YPrPb ? 
 There are two possible causes of these artifacts : interlaced to progressive conversion arteiacts or 2D comb artefacts. Interlaced to progressive conversion: The I2P does contain a smoothing filter to minimise artefacts but some artefacts can still occur. 2D Comb: The ADV7180/ADV7182/ADV728x video decoders are designed to be low cost analog to digital video decoders and as such they only have 2D comb YC separation filters. 2D comb filters are good at separating the luma and chroma information but artefacts such as the one you have highlighted are still possible. Solutions : 1) Use a deinterlacer in your back end processor rather than using the I2P block of the ADV7280. The backend processor will have to store an odd frame of video in a buffer, then store an even frame of video and then stitch these two frames together to generate a progressive field. This will minimise interlaced to progressive errors but will add a delay to your system. Be sure to introduce a line counter or similar software control to ensure that you do not get buffer overflows. 2) Modify some of the registers in the ADV7280 to try and minimise 2D comb this artefacts for your system. Try reading the Chroma filter, Luma Filter, Chroma Transient Improvement, Digital Noise Reduction and Luma Peaking Filter, and Comb filter sections of the ADV728x hardware manual. You may get some improvement but you will never be totally able to remove 2D comb artefacts. 3) Use an Analog Devices video decoder that uses a 3D comb filter e.g. ADV7842. 3D comb will result in fewer artefacts output to the screen. However a number of frames of video need to be stored in an external SDRAM chip in order for the 3D comb filter to work. This will add a delay from inputted video to outputted video. If it is custom board,then please refer to application note for layout design at https://www.analog.com/media/en/technical-documentation/application-notes/AN-1337.pdf 
 
 Thanks, 
 Poornima)