Post Go back to editing

Video 101 question

This question will no dobt make obvious my lack of understanding of HD video format...you patience is greatly appreciated.

Have a question regarding using the AD9380 device, actually its currently on an FPGA development board that I'm looking at.

I have a full HD HD-SDI (1920 x 1080 - 1080psf29,97 or 1080p30) input signal that will be converted to HDMI on the development

board prior to going into the AD9380. The output will be going to a native 1920x1080 LCD panel via RGB to LVDS converter on the

development board.  When I read the spec for the AD9380 it says:

     "Its 150 MSPS encode rate capability and full power analog bandwidth of 330 MHz supports all HDTV formats (up to 1080p and

      FPD resolutions up to SXGA (1280 × 1024 @ 75 Hz)."

In my application I must have full HD (1920x1080) getting to the LCD panel without scaling. What I don't understand is I thought

(maybe that's my problem ) that 1080p was, by definition, 1920x1080. This seems to conflict with the devices' SXGA (1280x1024)

spec. The only thing I can figure, until someone kindly corrects my limited understanding, is that the device can take in 1920x1080

but will only send out 1280x1024 max. However, I think it much more likely I have a misunderstanding rather than the device

having a lower resolution output than input.

Can someone please enlighten me to where I'm wrong.

Thanks

Tom

  • Hi Tom,

    It sends out what it takes in-- it's not a scaler.  If you give it a 1080p input, you get a 1080p output.

    It's probably the terminology that is confusing.  1080p is the top consumer video format that is within 150Mhz (it's 148.5 Mhz).  For FPD/VGA/Computer formats I think SXGA 75Hz is 135Mhz and when that part came out a while ago... the next format up would have been UXGA 60Hz which would be 165Mhz which would be out of spec. So SXGA was the top computer format.

    It's just giving the top end video / computer formats it supports.  It's all tied to the maximum pixel clock.

    If you are planning a new design, you should use ADV7842. AD9380 is many generations behind the latest.

    Dave

  • Dave,

    Thanks for the very helpful info and the ADV7842 suggestion...I get it now...the pixel clock or sample rate of the device (AD9380 or AD7842) must be greater than the inherent sample rate needed for a particular format.

    So when the spec says: "Pixel clock output frequencies range from 12 MHz to 150 MHz", then we know that

    1920x1080p 60 would work because the sample rate for that format is, as you mentioned, 148.5 MHz. Ok...

    That's great. Thank you kindly.

    Tom