Why do not CRT/LCD monitors come with USB?

  • Thread starter Thread starter Rahul
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Rahul

These days, every possible accessory seems to be "bluetooth" / USB
interfaced. But I've never seen a "USB" monitor advertised. (neither
bluetooth, of course) Neither CRT (who buys those!? :) ) nor LCD.

Why is that? A bandwidth limitation? Or a need that doesn't exist? I doubt
that is the reason since if I can want a USB headset why not a USB monitor?

Besides there are "good" quality headsets available even on bluetooth. Is
"acceptable-quality" sound transmission fundamentally a lower bandwidth
process than "acceptable-quality" images? What is the ratio of the max
bandwidth attainable over USB vs bluetooth vs "traditional-monitor-
connections".

I cannot think of any other peripheral that isn't available in a USB
version if not bluetooth. Do others have examples of they know? Just
curious....
 
Rahul said:
These days, every possible accessory seems to be "bluetooth" / USB
interfaced. But I've never seen a "USB" monitor advertised. (neither
bluetooth, of course) Neither CRT (who buys those!? :) ) nor LCD.

Why is that? A bandwidth limitation? Or a need that doesn't exist?
I doubt that is the reason since if I can want a USB headset why
not a USB monitor?

Besides there are "good" quality headsets available even on
bluetooth. Is "acceptable-quality" sound transmission fundamentally
a lower bandwidth process than "acceptable-quality" images? What is
the ratio of the max bandwidth attainable over USB vs bluetooth vs
"traditional-monitor- connections".

I cannot think of any other peripheral that isn't available in a USB
version if not bluetooth. Do others have examples of they know? Just
curious....
Click to expand...

http://www.xbitlabs.com/articles/other/display/samsung-sm940ux.html
http://www.everythingusb.com/samsung_syncmaster_940ux_11970.html

Google is not your enemy.
 
Rahul said:
These days, every possible accessory seems to be "bluetooth" / USB
interfaced. But I've never seen a "USB" monitor advertised. (neither
bluetooth, of course) Neither CRT (who buys those!? :) ) nor LCD.

Why is that? A bandwidth limitation? Or a need that doesn't exist?
I doubt that is the reason since if I can want a USB headset why
not a USB monitor?

Besides there are "good" quality headsets available even on
bluetooth. Is "acceptable-quality" sound transmission fundamentally
a lower bandwidth process than "acceptable-quality" images? What is
the ratio of the max bandwidth attainable over USB vs bluetooth vs
"traditional-monitor- connections".

I cannot think of any other peripheral that isn't available in a USB
version if not bluetooth. Do others have examples of they know? Just
curious....
Click to expand...

Shenan said:
http://www.xbitlabs.com/articles/other/display/samsung-sm940ux.html
http://www.everythingusb.com/samsung_syncmaster_940ux_11970.html

Google is not your enemy.
Click to expand...

Go a step beyond...
http://www.wi-fiplanet.com/news/article.php/3715636
 
Rahul said:
These days, every possible accessory seems to be "bluetooth" / USB
interfaced. But I've never seen a "USB" monitor advertised. (neither
bluetooth, of course) Neither CRT (who buys those!? :) ) nor LCD.

Why is that? A bandwidth limitation? Or a need that doesn't exist? I doubt
that is the reason since if I can want a USB headset why not a USB monitor?

Besides there are "good" quality headsets available even on bluetooth. Is
"acceptable-quality" sound transmission fundamentally a lower bandwidth
process than "acceptable-quality" images? What is the ratio of the max
bandwidth attainable over USB vs bluetooth vs "traditional-monitor-
connections".

I cannot think of any other peripheral that isn't available in a USB
version if not bluetooth. Do others have examples of they know? Just
curious....
Click to expand...

This monitor has a USB2.0 interface to drive the video display
(as well as the more ordinary and higher bandwidth interfaces).
It uses a compressed data stream, to compensate for the limitations
of USB2 bandwidth.

http://www.everythingusb.com/samsung_syncmaster_940ux_11970.html

You can also find display adapters, with USB on one end, and VGA
on the other end. The resolution options offered are not that
good, which is a limitation. Presumably one of those chips is
what is hiding inside the Samsung monitor.

Also, there is a subtle difference, between VGA, DVI, and USB. The
first two are being used to retransmit a full frame image, over
and over again. The USB is used to carry difference information
(repaint areas of the screen that have changed), because sending
the full frame over and over again, would make the screen impossibly
slow. As it is, USB devices like this, tend to offer a "slide show",
and you would notice the transmission method affecting your perception
of the experience.

Bluetooth is 3 megabits/sec max as far as I know. USB2.0 is 480 megabits/sec
theoretical, and somewhat less in practical usage.

http://en.wikipedia.org/wiki/Bluetooth
http://en.wikipedia.org/wiki/Usb

It wouldn't be fair or meaningful, to compare DVI to those two. But just
for kicks, a single link DVI uses three diff pairs RGB with data streams on them.
At a so-called 165MHz clock, each diff pair runs at 1650 megabits/sec, or
a total of 4950 megabits/sec. Dual link uses two instances of the interface,
for double that bandwidth (but dual link is not commonly used for your
average cheap LCD monitor). Just to offer some perspective with respect
to USB2.0.

http://en.wikipedia.org/wiki/Digital_Visual_Interface

Paul
 
Paul said:
Bluetooth is 3 megabits/sec max as far as I know. USB2.0 is 480
megabits/sec theoretical, and somewhat less in practical usage.
Click to expand...

Thanks Paul. Does anyone know of scales that compare the bandwidth required
to get an "acceptable" human-perceived level of sound vs video. Again,
harps on my point of whether video *needs* a higher bandwidth channel than
sound.

Do my eyes capture at a higher bandwidth biologically than my ears? Only of
academic interest.
 
Rahul said:
Thanks Paul. Does anyone know of scales that compare the bandwidth required
to get an "acceptable" human-perceived level of sound vs video. Again,
harps on my point of whether video *needs* a higher bandwidth channel than
sound.

Do my eyes capture at a higher bandwidth biologically than my ears? Only of
academic interest.
Click to expand...

Your telephone and the audio bandwidth it uses, should be evidence that
audio doesn't need much bandwidth at all. For example, an older
Unix workstation I used to use, had only an 8KHz sampling rate. And
yet I was able to listen to music while I worked, using it. An 8KHz
sampling rate, times 8 bits per sample, means only 64 kilobits/sec is
used per channel. Even USB 1.1 is enough to handle that, and in practice,
higher sampling rates or more bits per sample can be used.

I don't think I can answer your question about the human visual
system. For example, in this article, I don't see anything with
megabits/sec in it :-)

http://en.wikipedia.org/wiki/Visual_cortex

Paul
 
| This monitor has a USB2.0 interface to drive the video display
| (as well as the more ordinary and higher bandwidth interfaces).
| It uses a compressed data stream, to compensate for the limitations
| of USB2 bandwidth.
|
| http://www.everythingusb.com/samsung_syncmaster_940ux_11970.html

And what kind of support for this exists in Linux? X? DirectFB?


| It wouldn't be fair or meaningful, to compare DVI to those two. But just
| for kicks, a single link DVI uses three diff pairs RGB with data streams on them.
| At a so-called 165MHz clock, each diff pair runs at 1650 megabits/sec, or
| a total of 4950 megabits/sec. Dual link uses two instances of the interface,
| for double that bandwidth (but dual link is not commonly used for your
| average cheap LCD monitor). Just to offer some perspective with respect
| to USB2.0.

And even dual-link DVI won't be able to handle what is coming in the future
of video and TV (10+ years from now). Be prepared for a video display device
that can do extreme video, but takes its input in VNC (for desktop) or MPEG
(for video) formats over whatever connection medium is available as long as
it is fast enough. Ideally the display can have both at the same time, with
VNC providing the base layout, and MPEG for a specific video feed that can
be directed to whatever region of the display is desired (or the whole screen)
with the HDCP decoding done in the display, where needed. Then the OS only
has to layout the screen and pass the stream (which would be two way between
the display and video source when HDCP is involved).
 
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