LG LM760 3D TV 55″

Posted on 4 June 2012

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After a bit of research, I bought the LG LM760. Looks really good, with a very small bezel (although it is not as small as you would think if you look at LG’s pictures). Yes, there is a sheet on top of it, which you could use as a mirror (not a very bright one and it isn’t really a flat surface). It really is a lot more glossy then the LW series, so this might be a reason to bring it back to the store. And I found that there might be some other problems that you would not expect at this price range.

The LM760 comes with WIFI and a magic remote, which is nice for youtube. But I have to say, the remote does not work really perfect. And I read from others that ‘Flash-based web pages are too heavy for the included browser. Not a substitute for a regular PC. The experience is like having a very slow internet connection.’ You can also buy a cheaper TV and get a $ 300 netbook that has much better smart-TV functionality and will take a real webcam and wireless keyboard. What’s also nice is that it comes with support for  Wi-di (intel), wifi, wifi-direct (without router) and a smartphone app.

At this moment I couldn’t find a review of the LM760 but I found this:

First impressions

The bad:

  • problems with playback of true 3D .mov and .mp4 (mpeg4part2) files. also does not remember 3D settings
  • no PC gamma HDMI input like the smaller LG-DM2350D or the Philips 7606
  • problems with 24p and 50hz

3D playback

For playing the 3D material on the LG TV there are several options. I’ve tested with playback from the HDMI output of the computer on the PC input of the screen. Unfortunately, this screen does not ask if it is a computer that is attached and it looks like it does not remap the full swing hdmi signal to studio swing display, so there is no contrast in the blacks. Strange, as this is a dedicated PC input, so one would expect that they have this sorted out. I couldn’t find it in the manual, the only thing I found is this page about automatic 3D modes:

LG LM760 HDMI input specs

USB playback

Next up is a test of playback from USB. I’ve encoded a Cineform file set to ‘fields’ to a 25p prores file. This I converted to a h.264 .mov file with a max datarate of 15000 kbps. Didn’t work, got strange decompression artifacts in the LG that disable 3D functionality. I am sure the artifacts are because of the decoder of the LG: I do not see them when I play back from the computer. I tried 50i prores to h.264 max 8000 kbps. Now it is even worse. I also noticed that the left and right of the screen are slightly letterboxed. From USB, it does not recognise the 3D mode automatically. This might be because it is 25p and the manual only states 30p.

So up to manual selection:

LG LM760 USB input

25p top/bottom h.264

Even though it also states 30p only, it does work in 25p. Not with the above files, but I found another way: I thought it might have been the h.264 encoder or the .mov extension, so I made a mpeg4 part 2 .mp4 file. Same problems plus another one: less contrast (again the studio vs fullswing problem). I found that the best solution was to make a top/bottom file, this could be either a h.264 .mov or mpeg4 part 2 .mp4 at any datarate up to 20 mbps. Then will play back without problems, only you have to set it to the right 3D playback setting every time at the start of the file. The LG will not remember the settings.

25p row interleaved

The strange thing is that the manual states the USB input supports ‘row interleaving’ but that it doesn’t work when I have a file that is row interleaved. The interesting thing is that LG makes a difference between Row Interleaving, line alternative, Single frame sequential and field alternative. I don’t know this difference between the first two.

First thing is the horizontal frequency. I know from analyzing the sound of an SD TV that it is 625 lines * 25 fps = 15625 Hz. So 56,25 kHz is 56250 Hz / 50 fps = 1125 lines. This looks like a very old standard, but it seems that it is still part of the rec.709 specs.

25p mvc

Because the LG does support 25p which is not mentioned in the manual, I thought the USB port might also support frame packing or other 2x full HD formats. So next up was converting to a AVC MVC file with Sony Vegas. This .avc file is not seen by the LG. Then I tried making a AVCHD file, with .m2ts extension. This also is not recognised.

hdmi input

In the end, playback from a HDMI source seems to be best, as you can set the 3D settings just once. Make sure you disable any screensaver, otherwise you will have to set it again! I’ve found that I could make some changes to the color settings of the LG so the playback gamma is pretty like it should be.

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Posted in: S3d