This happens with ANY Pioneer AV unit. The problem is that Pioneer doesn't ground their shielding for the AV inputs inside the unit on the circuit board. No one knows why. I have even asked Pioneer Tech about this, they say it's a known problem.
The SIMPLE solution is to ground the outer shield of the RCA inputs. Either solder a 16-18ga. piece of wire to the outer shield of your cable, and ground it to the radio's ground wire, or CAREFULLY slice open just the outer shield of the cable, pull up some of the braided wire outer shielding, and solder a 16-18 ga. wire to that, and ground it to the radio ground wire.
NOTE that you do NOT need to do it to all three RCA inputs (Yellow, White, Red), just ground ONE of the shields on the inputs and will take care of the problem.
This will fix Audio buzzing, and will fix noisy video(lines scrolling thru picture.) You will commonly see this problem with an inverter and external AC source, but sometimes it occurs on portable units with no inverter involved.
Also, it is being common now to make factory AUX plugs in new cars work with these inputs, and Pioneer recommended to me that I make sure that when I make a splice RCA harness to adapt these factory 3.5mm audio jacks to a Pioneer deck, that I ground the shield as well. This will help the unit "trigger" on the AUX or AV inputs for the external audio source.