dvi vs component (again)

Archived from groups: alt.tv.tech.hdtv (More info?)

> Lastly, I thought all HDTV's were digital, but now I know that CRT's are
> not. Why aren't they digital? Looking through the ventilation cracks it
> looks like a computer is in the TV, which I figure there is. What is the
> difference between a CRT and plasma or LCD with the exception of the tube?
> Is it the tube that makes it analog?
>

The signal for all HDTVs arrives as a digital stream so the tuner of all
HDTVs is always digital. The difference between the CRT and other display
technologies such as LCD, DLP, LCOS is as you said, the tube. CRT takes the
digital image information and draws it on the screen, one scanline at a
time. The other display technologies have a pixel based display, so for
those TVs even the display is digital.

Archived from groups: alt.tv.tech.hdtv (More info?)

On Sat, 11 Sep 2004 22:46:15 -0400, "Eddie G" <mickeddie at
comcast.net> wrote:

>When I got my TV a few months ago I posted the question about DVI vs.
>component, and it started a really long discussion. I bought DVI because
>the cables cost me $6 from a web site and I am happy with them. The
>difference between dvi and component is where the signal is transferred from
>analog to digital, or something like that. Can someone please explain this
>to me, and what is the "supposed" difference? A bit clearer picture?
>
>And where does the conversion happen with component? With DVI?
>
>Lastly, I thought all HDTV's were digital, but now I know that CRT's are
>not. Why aren't they digital? Looking through the ventilation cracks it
>looks like a computer is in the TV, which I figure there is. What is the
>difference between a CRT and plasma or LCD with the exception of the tube?
>Is it the tube that makes it analog?
>
>Thanks,
>
>Eddie G

Lets say in some high end short wave radios they use some digital if
stages to eliminate noise It brings the radio signal in and converts
that analog audio. It does this by taking samples, then compressing
it. The circuit then digitally rebuilds the signal without the noise.
In this case it made back into a clean analog signal to be amplified
to the speaker.

Lets look at a HDTV. The digital signal is already compressed. Put
through the channel selector then passed through various stages of
amplifiers. Uncompressed then most likely converted to a analog
signal. I would say here the analog video signal has to be a ac type
signal for the demodulator color section of the tv before going to the
picture tube. The picture tube basically works on a dc biasing type
voltage to draw the beam to the screen. The analog signal is applied
to the grids for the various colors and basic video picture. The yoke
around the neck of the pix tube sweeps the beam back and forth to make
the picture fill the screen.

Now with a DLP set I'm wondering if its digital though the computer
chip and to the mirrors. Wonder if those mirrors are made to work
with tiny ac pulses, again perhaps analog.

I'm sure with the way HD is going we will see some form of all digital
sets in the future.

hdtvfan

Archived from groups: alt.tv.tech.hdtv (More info?)

Eddie G wrote:

> Lastly, I thought all HDTV's were digital, but now I know that CRT's are
> not. Why aren't they digital?
>
>


Regardless of the type, all display devices produce an analog image.
Digital type displays such as DLP or LCD type provide digital addressing
and only control where on the screen the image is displayed; but the
image itself is analog. Parameters such as picture size, aspect ratio
and linearity should easier to control with digital addressing; but the
main function, to convert digital video to analog, remains the same for
all digital TVs. Your eyeballs are analog, therefore the display also
must be analog. The day you are born with digital eyeballs is the day
when "true digital" displays can be made.

Archived from groups: alt.tv.tech.hdtv (More info?)

"Eddie G" <mickeddie at comcast.net> wrote in message
news tmdnSXc6-_gJd7cRVn-tA@comcast.com...
> When I got my TV a few months ago I posted the question about DVI vs.
> component, and it started a really long discussion. I bought DVI because
> the cables cost me $6 from a web site and I am happy with them. The
> difference between dvi and component is where the signal is transferred
> from analog to digital, or something like that. Can someone please
> explain this to me, and what is the "supposed" difference? A bit clearer
> picture?
>
> And where does the conversion happen with component? With DVI?
>
> Lastly, I thought all HDTV's were digital, but now I know that CRT's are
> not. Why aren't they digital? Looking through the ventilation cracks it
> looks like a computer is in the TV, which I figure there is. What is the
> difference between a CRT and plasma or LCD with the exception of the tube?
> Is it the tube that makes it analog?
>
> Thanks,
>
> Eddie G

analog means that information is carried by a voltage that changes over time
so in the case of rgb, the brightness of the red is determined by the
voltage on the r cable, green by g and blue by b

this just happens to be how a crt works... the intensity of the electron
beam (brightness) changes as the current into the tube's cathode emitters
changes - analog

digital means that the information is coded not into a simple analog
voltage, but into a series of on/off , 0/1 bits and an encoding scheme to
map these bits into information. HDTV is sent digitally, either over the air
or on cable. This is because it's really tough to carry a decent HD quality
analog signal very far. You can put a DVI on a CRT, but then the display
processor still needs to convert the digital information to analog for the
CRT

so to take digital HD image information and display it on a crt requires a
Digital to Analog conversion... typically in the STB and the analog is sent
down the component cables.

but SOME display technologies, like plasma and dlp are inherently digital...
nowhere is that time varying analog signal needed as the brightness off the
pixel is determined by a digital pulse code modulation of the plasma cells
or mirrors.

so with a pdp or dlp, it makes no sense to take a digital signal, turn it to
analog and then redigitize it for the display better to recode the digital
signal without losses or errors and send it DVI to the display's processor.

LCD's are much more complicated and internally are actually a blend of
digital and analog - but they are best linked digitally since the
complicated stuff takes place in the digital part of their display driver
electronics

hope this helps

Archived from groups: alt.tv.tech.hdtv (More info?)

"numeric" <numeric@att.net> wrote in message
news:414436C6.3020602@att.net...
>
>
> Eddie G wrote:
>
>> Lastly, I thought all HDTV's were digital, but now I know that CRT's are
>> not. Why aren't they digital?
>
>
> Regardless of the type, all display devices produce an analog image.
> Digital type displays such as DLP or LCD type provide digital addressing
> and only control where on the screen the image is displayed; but the image
> itself is analog. Parameters such as picture size, aspect ratio and
> linearity should easier to control with digital addressing; but the main
> function, to convert digital video to analog, remains the same for all
> digital TVs. Your eyeballs are analog, therefore the display also must be
> analog. The day you are born with digital eyeballs is the day when "true
> digital" displays can be made.

no
while the image out of an lcd is analog, the images out of a plasma or dlp
is actually digital
they don't vary in brightness so much, but in the time they are off and on

it is your eye and brain that convert the rapidly flashing digital light
pulses into an analog image

Archived from groups: alt.tv.tech.hdtv (More info?)

Randy Sweeney wrote:
> "numeric" <numeric@att.net> wrote in message
> news:414436C6.3020602@att.net...
>
>>
>>Eddie G wrote:
>>
>>
>>>Lastly, I thought all HDTV's were digital, but now I know that CRT's are
>>>not. Why aren't they digital?
>>
>>
>>Regardless of the type, all display devices produce an analog image.
>>Digital type displays such as DLP or LCD type provide digital addressing
>>and only control where on the screen the image is displayed; but the image
>>itself is analog. Parameters such as picture size, aspect ratio and
>>linearity should easier to control with digital addressing; but the main
>>function, to convert digital video to analog, remains the same for all
>>digital TVs. Your eyeballs are analog, therefore the display also must be
>>analog. The day you are born with digital eyeballs is the day when "true
>>digital" displays can be made.
>
>
> no
> while the image out of an lcd is analog, the images out of a plasma or dlp
> is actually digital
> they don't vary in brightness so much, but in the time they are off and on
>
> it is your eye and brain that convert the rapidly flashing digital light
> pulses into an analog image


My prior reply needs a little more explanation. I think that the term
"digital display" is misleading in the sense that it implies that analog
type errors are avoided. Not true.
Even the DLP type produces digital to analog conversion errors from a
digital video source. The digital video is converted into a pulse width
modulated signal to switch the micro mirror on and off at a rapid rate,
which in turn is integrated by the eye. The latency or response time of
the eye is longer then the micro mirror-switching rate and is simply
integrated by the eye. The resultant image is nonetheless analog. Motion
pictures use the integration effect of the eye to produce the illusion
of motion. As you say the dlp display switches the micro mirror on and
off; but the effect is analog with the same type of errors (noise,
linearity, quantizing error ...etc) as a D/A converter and a
conventional picture tube type display. If the eye were truly digital,
your brain should be able to record the digital video and save it for
later play back  .