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ADV7842: Big jitter on LLC for HDMI

Question asked by Sasa on Feb 19, 2016
Latest reply on Mar 4, 2016 by Sasa

I see big jitter on LLC (pixel clock) in “HDMI-COMP” mode when signal is present. Why? Where to find?


In HDMI FreeRun mode for 720p/1080i jitter is absent (after setting HDMI.44 = 0x85 - In COMP-Mode jitter is absent at all (with signal or in freerun-mode, 576i/720p/1080i).


Output pixel-bus of ADV7842 is connected to ADV7513. On TV for 720p/1080i I see periodic resync, white pixels in “HDMI-COMP” mode with signal. Component-input of ADV7842 works well (source video for HDMI and Component is the same – Duna Blu-Ray player).


LLC = 74.25MHz (720p, 1080i).


IO.PRIM_MODE[3:0]=1 (COMP-Mode),

IO.VID_STD[5:0]=0x13 or 0x14 (for 720 or 1080)


For SD-Mode (576i50) and HDMI-COMP Mode jitter on LLC a little less…


After MPEG coding-decoding (clearing clock) ADV7513 with the same settings works well – picture on TV is clear and without resync.


In attachment:

"HDMI - HD.png", "HDMI - SD.png" - LLC from HDMI with signal HD (1080i) and SD (576i), big jitter.

"HDMI FreeRun, COMP - HD.png" - LLC from HDMI in FreeRun mode and COMP in any mode (with signal and no) for HD (1080i), no jitter.

"COMP, CVBS - SD.png" - LLC from COMP and CVBS for SD (576i), no jitter.

"HDMI FreeRun - SD.png" - - LLC from HDMI in SD (576i) and FreeRun mode, big jitter.