I live in Montreal, Canada, and I too recently purchased an LG 47LM4600 about a month ago. I am no stranger to many of the issues that have been brought up here, and I may be repeating a lot of what has been said over the course of this lengthy thread (all apologies), but I did some digging and found out some things that LG may have been keeping hidden from the public. I wrote this posting just to clarify a few things with, as they call it, hard evidence (confused, nonsensical and self-contradictory statements from random LG customer reps probably wouldn't count in court) for those who may be interested in filing a class action suit. Sorry if the post is long.
There seems to be a bit of confusion over what Trumotion actually does as well as the difference between frame rate and refresh rate. The refresh rate is an intrinsic characteristic of the television, and refers to the number of images that may be displayed in sequence over a period of time (commonly one second, hence the units of Hz). The frame rate on the other hand is mainly a function of input. For instance, many movies are shot at 24 frames per second and, ideally, that is how they should be viewed.
The two are related to some degree. Say, for example, you are running a natively 24fps movie on a purely 60Hz set. A problem arises because the TV is displaying images at a rate that is faster and unsynchronized, leading to a very uneven picture. To compensate, the external player outputs 60 frames per second by making copies of some of the frames so that there is a sufficient number of images to cover an entire second; this is known as a pulldown and is part of a family of techniques known as Telecine, and can contribute to a lot of motion artifacts which may be noticeable on large LED sets. Some companies also use another technique called "Black Frame Insertion", in which the individual LEDs are shut off in a particular sequence in between frames at a rate that's fast enough to go unnoticed by the eye. This allegedly reduces motion blur, but I've never seen it at work firsthand myself. LG claims to use it in their LM series (which, as you will find out below, would preclude Trumotion from functioning), but I have my doubts.
Luckily, a lot of 60Hz sets (including the 47LM4600) implicitly support 24fps, so a lot of motion jitter can be eliminated by buying a DVD/Blu-ray player that outputs 24 fps. Conversely, live events and soap operas are filmed at 60Hz, so they'll look fine and jitter-less on 60Hz televisions in any case. Historically, the discordance between frame rate and refresh rate is due to the fact that when CRT television sets were first released, home video and broadcasting of movies weren't common, so sets didn't need to be 24Hz. When watching movies at home became popular (also, TV programs began to gradually adopt 24fps), the recordings were converted using the same pulldown technique before being aired or released on VHS or early DVDs and audio was adjusted accordingly. Later DVD and Blu-ray releases weren't necessarily converted since newer players and TVs were capable of handling native rates.
Those of you who are good with numbers will notice that 120 is both an exact multiple of 24 and 60. This is a good observation, but not exactly all that meaningful (sorry!). Again, because there is less input information per second than the television natively processes, the resulting image would still suffer from jitter due to frame duplication unless the content were 120fps (true 120fps content is extremely rare), and this is where Trumotion comes in. As many have already pointed out here, Trumotion is software that is installed on the television set that involves a little math (I won't go into detail here). It interpolates a sequence of frames, which in the end results not in duplicates of frames or black frames, but instead artificial frames that best approximate an intermediate state between two frames (think of it as seeing a person at point A and then at another point B; interpolation would involve imagining all the positions in between point A and B). Basically, it makes lower frame rate content look smoother, and would save studios money from having to do the process themselves in post-production. Physically, the algorithm is located in a processing unit called a Frame Rate Converter (AKA FRC on wiring diagrams). Obviously, this can be computationally demanding at times, can create a lag and can be prone to errors on occasion, but I do have to tip my hat off to LG when I say that those issues are quite negligible (what can I say? Credit where credit is due)...
... Of course, that praise assumes the TV actually has Trumotion or is even capable of running it. Now, you don't have to be a genius to realize that interpolating 24 or 60 frames to obtain a total of 120 frames is pointless unless, well, your TV can display 120 images per second (i.e. 120 Hz refresh rate), and this is where LM owners have gotten pissed. I can't speak for the entire series, but the truth of the matter is that Trumotion cannot work on the 47LM4600 because it is not a 120Hz television; it is actually a 60Hz set. I blame LG for not making this more obvious to the average consumer (which I would have described myself as a month ago); if you consult the final pages of the owner's manual, you will see a list of horizontal and vertical frequencies (AKA refresh rate) based on input type and resolution. All numbers for vertical frequency are either 24 or 60, but never past that. The service manual (which is supposed to be kept internally at LG, so don't ask how I got hold of it) confirms this. If you look at point #5 in the following specs table, you will see "FHD + 60Hz", which translates to "Full High Definition at 60Hz".
Contrast this to the 47CS570 (a model I bought my parents for X-Mas one year), which as you can clearly see from its own service manual is actually 120Hz. Incidentally, it implements Trumotion quite well:
This alone is enough proof to go after LG for falsely advertising their product, as their official specs sheet (I kept a copy sent to me by a sympathetic but admittedly helpless customer service rep at Adorama Camera) clearly states "Trumotion 120Hz", which is physically impossible on this set. However, the icing on the cake lies in the official schematics in the service manuals. As I said before, motion interpolation requires the physical existence of a Frame Rate Converter/FRC chip. If the 47LM4600 were capable of supporting Trumotion (even though I already proved it can't), one would expect to find FRC connections in its schematics. As I expected, it is nowhere to be found. However, the term "120Hz" is found in the following excerpt I pulled from the service manual that seems to describe several physical electronic switches that are used for activating or deactivating certain features on the TV, such as 3D. One would expect a connection to a FRC, but it is nonexistent, so the 120Hz pathway is useless, and physically opening the chassis and turning the switch on would most likely result in absolutely nothing (or, even worse, would null the warranty and damage the set). Take a look:
Compare this to the same set up in the aforementioned 47CS570, where you can clearly see a "NO FRC vs a "FRC_HW_OPT" option. This refers respectively to the Low and High Trumotion settings. See for yourself:
Some of you may (rightfully) raise the point that Trumotion was added successfully to a firmware update for the 55LM6700 which did not come with the feature to begin with and was, on top of everything, a 60 Hz panel (confirmed by the service manual). I have my own theory, so take it for what it is. In the schematics for the LM6700, there is an FRC unit. It's actually "SoC internal FRC", which is an acronym for "system on a chip", otherwise known as an integrated circuit. Basically, much as integrated on-board GPUs are to their bigger counterparts, the SoC FRC may be a less powerful version of the unit used for motion interpolation in higher end sets. Therefore, it is possible that the Trumotion version installed may be for interpolating 60 images from 24 fps content instead of 120. Given that 60Hz already looks fairly smooth and lifelike (at least to me, anyways), it would be hard to tell the difference.
Given all of this, I think I finally understand what LG is doing. Once again, personal theory only, so take with a grain of salt. They probably manufactured the 47LM4600 at the same time as some of the higher end LM models using the same circuitry in order to cut back on costs and avoid having to design multiple boards. Since what really costs money is the processing unit that interpolates the images, LG just simply omitted it in the lower end models to keep the price low, which explains the absence of an FRC unit despite a 120Hz option, thereby requiring its permanent disabling.
So, what's the overall message? Well, for one, I've learned my lesson, and not only will I boycott LG until they clean up their act, but I've learned to be aware of numbers without any actual meaning and to beware of false advertising from companies who one had a reliable image. Also, I will consult specialized technical reviews before buying electronics, as opposed to consumer reviews. Judging by some of the reviews I've seen for the 47LM4600, I have a feeling that many customers are still unaware that they have purchased a misrepresented product. Furthermore, I don't think a firmware update will ever come, nor would one even fix the issue in any case.
This is more than a gross oversight on LG's behalf. The evidence I have provided clearly points towards a cheap marketing ploy designed to boost television sales. This has seriously damaged their reputation in my eyes and, yes, I think there is a solid legal case against them.
However, seeing as I live in Canada and that States consumer laws may not apply to me nor may Canada's laws cover an imported product (last time I'll ever do that!), I may have to face looking on the bright side of things, and there is a bright side. For one, there are much worse problems I could face. I'm healthy, educated and live a pretty good life in a developed country, so it helps to put things in perspective (a good strategy for most of life's problems, I may add
). Also, as I said before, most if not all LM panels can handle 24fps or 60fps content just fine, if you have appropriate equipment, and you will be able to watch things the way they were meant to be watched. I don't think it's likely that we will see native 120 fps material any time soon. Movies are only starting to use 48 fps, known as High Frame Rate or HFR. The last movie in recent memory that employed this was The Hobbit - An Unexpected Journey, but I think this was a movie theater exclusive and didn't translate to home video. Finally, the 3D (including 2D conversion) is impressive. and HD images look spectacular (including upconverted DVDs). For the price I paid, I could have gotten a worse TV.
All the best.Edited by Lemming88 - 8/3/13 at 10:46pm