Originally Posted by totesmuhgoats
Thanks for the reply and the suggestions. You are right about the Game mode reducing the input lag introduced, there is still some input lag for 24p content that isn't present for 30p content, probably because 30fps content is doubled to 60 at my set top box and then sent to the tv, whereas 24p is processed with either 3:2 pulldown or 3:3 if real cinema is enabled at the TV. I think I am simply going to migrate to an HDMI receiver at some point where the lip sync can be done automatically. There are inexpensive used ones on CL that have all the features that I need. For now I am just using the optical out on the TV.
I have also found, if you are wanting to set the delay for an older receiver that I was wrong in my estimation earlier. The input lag is actually somewhere between 300 and 350 milliseconds (if you are passing 24p and have Real Cinema enabled with all the ugly post processing such as TruMotion and noise reduction off).
To reiterate, make sure you're using BOTH Game Input (or PC) and Game Picture Mode. This will be the best test of how low you can reduce your lag off your particular hardware.
I have some issues with the way LG puts out unclear documentation. This has led to some real confusion on what Real Cinema and 2:2 or 3:3 pulldown on the this TV is or isn't. I've tested bluray material playing at 24p on this TV in picture modes that make Real Cinema and Trumotion available and modes that don't make them available. Further, I've tested the picture with Real Cinema on and off (w/ Trumotion always off) in the modes that make it available. The modes without Real Cinema available have no noticeable audio sync issues while sync issues are present in the extreme in modes with Real Cinema, whether Real Cinema is turned on or off. Again, this is 24p playback, not native 60hz.
In terms of picture quality, the three states tested (Real Cinema unavailable, Real Cinema available and on, Real Cinema available and off) showed no discernible difference. Playback at 24p was equally smooth in all states. The TV was flicker-free in all states. I've posted in the past that it's hypothesized that this TV outputs 24p at 72hz using a 3:3 cadence. The 72hz is key, as it's widely known that the nature of plasma causes major flicker issues if 24p is actually played back at 24hz. The flicker is less intense but noticeable to many when this is doubled to 48hz using a 2:2 cadence. And, finally, absent to most everyone when it tripled (and beyond) to 72hz. Considering the lack of flicker and equally smooth playback in the three states I tested, my theory is that this TV locks this feature in when playing back 24p - there is no way to turn playback at 3:3 cadence on or off. The choice of Real Cinema is immaterial to 72hz playback as that is always the case during 24p playback.
I believe that picture modes that leave Real Cinema and Trumotion available introduce post-processing that only relates to interlaced signals (Real Cinema) and picture smoothing via frame interpolation (Trumotion). As frame interpolation is really only necessary on LCD/LED TVs to cancel out motion blur, Trumotion can always be left "off" in our plasmas. Real Cinema, on the other hand, is really only useful for inputs that receive an interlaced signal - cable/sat boxes, TV antennas. Real Cinema allows detection of the film based content behind the interlaced signal and then outputs a progressive signal at a 2:3 cadence to 60hz. Real Cinema does not take an interlaced signal and then output it at 24p. As certain devices will only ever output progressive signals - game systems, bluray, roku, apple - and play back content streaming the original progressive source file (as in Netflix streaming a movie), these devices will never need Real Cinema to detect interlaced signals that simply aren't there. However, any picture mode on this TV that leaves Real Cinema and Trumotion as options (whether checked or unchecked) creates a post-processing bump - an unnecessary bump for many modern devices.
LG, to my frustration, has confused the issue in its documentation by coupling the terms 24p and Real Cinema together. Real Cinema only detects the original 24p content behind an interlaced signal. It is NOT necessary for 24p playback of actual 24p material such as bluray movies. Choose a picture mode without Real Cinema for your bluray players and set-top devices that will only ever receive progressive signals.