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5878 Discussions

Can not get HDMI IP to output image at 4k 60fps



I would like to know the following.

For a 4k 60fps the following values are used :

pixel clock : 594MHZ 

Total horizontal count : 4400 pixel clocks

Visible pixel count       : 3840

Horizontal front porch : 176

Horizontal back porch : 144

Horizontal sync             : 88

Total vertical count  : 2250 vertical lines

Visible line count      : 2160

Vertical front porch : 8

Vertical back porch : 72

Vertical sync             : 10

The IP (on Cyclone 10GX) accepts 2 pixels per clock.

what would be the correct clock frequency and count values the IP needs to receive in order to operate correctly at 4k 60 fps.

Another issue I am having is what are the infoframes values I need to set for the IP to operate at a 4k 60 fps, if at all. Does the IP need the info frames in order to output the mentioned resolution.

And last but not least I would like to know what I am suppose to see on the transceiver output of the clock signal since when connecting this line to a scope I do not see a clock signal.  

Any help would be appreciated.

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2 Replies


Welcome back and fully understand the challenges to work in this COVID pandemic period.

One thing I forgot to mention is HDMI IP max supported video resolution is 4k@p60 with 8 bit per colour (bpc)

  • Are you using 8 bpc ? Any higher bpc setting will exceed HDMI bandwidth limit unless you lower down the video resolution

Next, Pls see my reply below.

  1. Regarding HDMI IP clocking input
  • All HDMI clocking calculation can be found in HDMI example design doc (table 14, page 23)
    • https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/ug/ug-dex-hdmi-c10gx.pdf
    • I also calculated the frequency for you but I guess you miss out my earlier reply in older forum post
    • The most crucial clock will be the link_speed_clock (ls_clk) and video_data_clock (vid_clk)
    • For your 4k Pixel clock = HDMI TMDS clock = 594MHz
    • Then you can basically use the formula shown in page 23/24 to calculate required ls_clk and vid_clk
    • ls_clk = TMDS clock frequency/ Symbol per clock = 594/2 = 297MHz
    • Assume you are using 8 bit per colour with colour depth factor = 1
    • vid_clk = TMDS clock/ Symbol per clock/ Color depth factor = 594/2/1 = 297MHz
  1. Regarding how to transfer video data to HDMI IP
  1. Regarding infoframe data transfer via Aux interface
  • This is question back to your application requirement on how you plan to control the general control packet, video or audio info frame packet
    • During normal operation these inputs should be static, and only change if the qualities of the video stream change (such as changing the color depth)
    • The HDMI IP Core converts these inputs into Data Island packets and transmits them during Data Island periods
    • If these ports are not controlled by the user or tied to 0, the HDMI core will generate default values for these packets compatible with the HDMI Specification 1.4b.
    • So you can tie this interface bus input to zero if you have no plan to use them
  1. Regarding no output clock from transceiver channel
  • Something is wrong somewhere. You should see some clock output
    • You can use example design to validate your hardware system
    • ensure all FPGA clock, reset and power is supply correctly





For the transceiver output clock you need to make sure that you are terminating it to the scope.  HDMI is a CML (Current Mode Logic) so many of the HDMI transceivers require a 100ohm differential termination for it to be present.  


As indicated those are the correct pixel clock frequencies required for 4k@60Fps.  I recommend to get things up and running in this area quickly is a Test Pattern Generator Frame Buffer and then the Clocked Video Out.