[geeks] 24 inch monitors

[Joshua Boyd]

On Jan 1, 2008, at 12:26 PM, Shannon Hendrix wrote:
>
> In fact, I could return my current monitor because it has a timing
> problem that largely doesn't affect me.  They'll ship me a new one.
>
> I have not totally dismissed a Samsung S-PVA display, but they do have
> a couple of issues that worry me.
>
> I always do this before buying something... :)
>
> BTW: you guys should read about input lag with LCDs.  I knew that
> sometimes large LCDs and LCD TVs bothered me when playing games, or
> even video or photo editing, but I didn't know exactly why.
>
> The short version: LCDs take each "frame" and have to process the
> data, perhaps several times over, before displaying it on the screen.
> Sometimes this processing overwhelms the CPU/DSP in the LCD and it can
> get as many as 15 frames behind.
>
> This is called "input lag", and it can range from not noticable, to
> horribly annoying, depending on what you are doing.
>
> Manufacturers don't like to talk about it, and do not publish this
> specification because industry standards do not currently require them
> to.
>
> The worst lag occurs in LCD TVs during interlace and progressive scan
> conversion.
>
> A typical game on an LCD TV can be as much as 15 frames ahead of what
> the TV is displaying.
>
> For computer LCDs, it is usually 5 frames or less.
>
> Here is something really interesting: if the visual input lags
> slightly behind sound, it induces stress and anxiety in human test
> subjects.
>
> Next time you are watching a horror movie, or playing a spooky game,
> you might want to deliberately create this effect for fun... :)
>
> Conversely, when sound is lagging behind visual input, humans tend to
> relax.
>
> Off topic, but I thought that was interesting.
>
> It would be interesting to see if/how often movie creators make use of
> this.

It is not the job of the movie makers to adjust for your TV being  
off, especially since it is off an inconstant amount.  Besides, your  
sound system may be delaying the audio as well.  I don't know about  
all AC3 decoders, but the official Dolby unit that I have at work  
takes 6 frames to decode.  I believe the encoder took 4 frames.  I  
had at one time measure a Creative Labs decoder, but I forget the  
number.  That is one thing that is much nicer about Dolby E (2 frames  
in either direction).

Plus, as you mention, TVs don't delay by a constant amount.

Although I've never seen a TV that would delay by a full half second.