glxgear and glxinfo confusion

[les]

On Wed, 2012-01-25 at 01:42 +1030, Tim wrote:
> On Mon, 2012-01-23 at 11:58 -0800, Joe Zeff wrote:
> > Motion Pictures are shown at 32 fps and nobody complains about 
> > flickering
> 
> Not quite.  Films are usually shot at 24 frames per second, and shown
> back at a multiple of that.  i.e. Each frame is usually strobed two or
> three times, so that you see 48 or 72 frames per second.  That makes the
> strobing mostly unnoticeable to most people.  Higher strobe rates could
> be used, but then you'd have a dimmer picture (the light being "on" for
> less per second, in total, than other rates).
> 
> (I work in video/television production, and occasionally get to play
> with film, too.  And just last night, had the pleasure of restoring a
> vintage 4-plate 16mm Steenbeck to working condition, to the delight of
> the owner.)
> 
> > there are people who claim that anything less than 70 
> > fps on their monitor flickers.
> 
> It depends on the monitor.  CRTs have a short persistence screen that
> glows for X microseconds, and fades away.  The persistence rate can be
> manufactured to suit how many frames per second the screen will be used
> at.  Multiscan monitors are less optimal, it'll try to have a
> persistence rate long enough that the slowest scan speeds don't show
> motion blurred pictures, and so that highest scan rates don't flicker.
> But they don't always manage that, or manufacturers might just use an
> unsuitable tube.  Hence why people notice how their computer monitor may
> flicker horribly at a 60 Hertz rate, yet their home TV doesn't
> noticeably flicker, but runs at the same 60 Hertz rate.  Likewise for
> people in 50 Hertz countries.
> 
> You can find, as I did, that some multiscan monitors are horrible at
> their fastest rate, giving me a migraine in moments.  Yet okay at one of
> the middle rates.  It's not just that you notice a flicker, but it's at
> a rate that disagrees with some brainwaves.  Perhaps in conjunction with
> some other strobing source in the room (such as a beat pattern between
> the screen and fluorescent lighting, all running at different rates).
> 
> I suppose the easiest way to give an analogy of that is with sound
> waves.  Many people find fingernails scratched down a blackboard to be
> cringeworthy, yet other people are not bothered by them in the
> slightest.  It's not a particularly loud sound, but it just happens to
> trigger an unpleasant reaction.  And if you change the pitch of the
> squeal, a bit, and you change how that affects people.
> 
> LCDs, and some other flat panel technologies, don't really strobe at
> you.  The pixels are illuminated as required for the picture, and stay
> at that illumination until they're redrawn by the next frame.
> 
> > I've always considered them the video equivalent of the audiophule,
> 
> Was that a mispelling of audiofile, or a joke of audio+fool?  ;-)
> 
> > who claims he can hear the difference between regular cables and gold
> > ones even after a scope shows the output to be identical and he's seen
> > the display of the two sine waves.
> 
> Well, some measurement techniques do not show up certain audio issues.
> But I agree that you just ain't gonna hear the difference between gold
> and aluminium audio wires, simply because they're different metals.  Nor
> are you gonna hear various other silly differences.
> 
> You can notice differences when there's resistance changes, as anything
> louder sounds slightly better (as a subjective comment).  But then you
> can simply turn your volume control up a tad, and have exactly the same
> effect, without buying $400 speaker cables.
> 
> Just where in the chain cables can have an effect depends on various
> things.  Resistance in the speaker wires affects speaker damping
> (unwanted bass speaker resonance) as well as volume.  Resistance and
> capacitance in the wiring between amplifiers and other decks can affect
> tone, depending on the design of the circuit around them (capacitance
> across high impedance circuitry can muffle the treble).  But it'd have
> to be pretty awful cable to become seriously noticeable.
> 
> A true audiophile knows that the weakest link is actually the speaker,
> itself.  Transducers are not perfect, and some are far worse than
> others.  And $400 cables aren't gonna get around whatever wiring has
> been used inside the cabinet, either.
> 
One thing I have to interject here is that a 'scope ( Oscilloscope) will
not show you the fidelity of a signal.  You need a spectrum analyzer.
You cannot easily see less than about 1% distortion or phase errors on
an Oscilloscope, yet the human ear is capable of about 60dB detection of
both phase and amplitude.  Some people are even better than that.  For
reference 60dB (power) means a noise level of 7uv on a 7v signal (about
6w on 8 ohms.)

The human senses are remarkably sensitive, and those who have greater
than normal capabilities are truly capable of discerning minute
differences between similar things.

Regards,
Les H