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ADV7343 CVBS Video Output Quality

Question asked by ranaya on Jul 13, 2017
Latest reply on Nov 27, 2017 by ranaya

Dear All,

 

Hi, I am using ADV7343 encoder as a CVBS converter interfacing through 24 bit pixel data bus with IMX6 processor. My requirement is to preserve the video and texture quality as much as possible. The CVBS output is meant to connect to a 800x640 lcd panel which accepts NTSC and PAL videos. I am only interested in CVBS video mode !!!

 

So from the processor side, I set the timing for 24bit parallel pixel bus in this way for NTSC :-

> ref_rate - 60, pclk - 37037, h_active - 1440, v_active - 480,  hb_porch - 110, hf_porch - 35, vb_porch - 42, vf_porch - 1, hsync - 129, vsync - 2 (values in number of pixel clocks in pico seconds, these were obtained by observing SD NTSC test pattern oscilloscope signals !)

 

> use HSYNC low active and VSYNC low active 

 

The i2c code I use to initialize the encoder is :

0x2B 0x17 0x02    # Software reset.
0x2B 0x00 0xFC   # All DACs enabled. PLL enabled (16 ^ ).
0x2B 0x01 0x00    # SD input mode.
0x2B 0x02 0x10    # RGB output enabled. RGB output sync enabled.
0x2B 0x80 0x10    # NTSC standard. SSAF luma filter enabled. 1.3 MHz chroma filter enabled.
0x2B 0x82 0xC9    # Pixel data valid. RGB and CVBS/Y-C out. SSAF PrPb filter enabled. Active video edge 
0x2B 0x87 0x80    # RGB input enabled.
0x2B 0x88 0x10    # 24-bit RGB input enabled
0x2B 0x8A 0x0C   # Timing Mode 2 (slave). HSYNC/VSYNC synchronization

(NTSC sub FSc addresses are set by default)

 

The output I get from the LCD screen is shown in LCD_OUT.png file. As you can see the texts are not visible in some of the layout fields. Questions I have :

 

1. Although standard NTSC is 720x480 (525i), why the encoder returns 1440x480 in NTSC test-pattern mode ? I am using the same timing in the test pattern to configure host processor pixel output. 

 

2. Can we improve the output quality by changing further settings in the encoder ? Can this be achieved using another resolution lcd accepts ?

 

Thanks in Advance

Anuradha

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