[GTALUG] war story: fixing an LCD TV

[D. Hugh Redelmeier]

| From: Lennart Sorensen via talk <talk at gtalug.org>

Thanks for this informative message.

| To: D. Hugh Redelmeier <hugh at mimosa.com>, GTALUG Talk <talk at gtalug.org>
| 
| On Sat, Jun 01, 2019 at 05:39:15PM -0400, D. Hugh Redelmeier via talk wrote:
| > HDR (High Dynamic Range) means a confusing variety of things,
| > especially after marketing has had at it.  But "normal" computer
| > pixels have 8 bits per colour in each pixel.  HDR often means 10 bits
| > per colour in each pixel.  So if you care about colour, you might want
| > HDR.
| 
| 8bit HDR does exist, but is rarely used since it tends to cause color
| banding.

How would it qualify as HDR?  OK: I know, HDR is anything marketeers
think that they can get away with.

I guess dithering can sort-of add a couple of bits.

| > You also need to worry about chroma subsampling (TVs often do this).
| 
| As long as you have HDMI 2.0 you should be able to use 8bit per channel at
| 4K and 60Hz without chroma subsampling (which ruins the clarity of text).

My (cheap, old) Seiki SE39UY04 TV is limited to HDMI 1.4.  So at best
it can do UltraHD at 30Hz, with 4:2:2 chroma subsampling.  I don't
know its LCD technology.

So it should be bad.  But for my usage, it seems pretty good.

- I don't have a lot of dynamic content on my screen, so slow refresh
  doesn't have a lot of effect.  The mouse cursor movement isn't as
  smooth as it would be with faster refresh.

- almost nothing I do exposes the limitations of chroma subsampling.
  Text is the killer test case but foreground and background for most
  text differs in luminance (full resolution), not chromanence (reduced
  resolution).  Some artistic creations have text that renders badly
  but even then, most artistic creations use quite large text.  In my
  browsing, I've only encountered this once or twice.

As far as the type of panel, I don't know.  I've googled for the code
on the panel and get only a few hits, all useless.

The electronics are sufficiently modular that I wonder if I could
graft a HDMI 2.0 T-Con board and processor board, to get a better
system.  I might do it if someone else pioneered.

Someone else hacked his/her SE39UY04 and discovered that it's running
Linux and can be modded: <http://www.zeroepoch.com/blog/se39uy04>