TV to VGA Conversion -- why so hard/expensive Part 2
In part 1 of this question, Hardware/Q_21815285.html, I asked for electronic descriptions of why it is so expensive to convert TV signal to run on a VGA monitor. You can buy a simple $5 cable that converts from VGA to TV scan lines, so if that is so simple to do for $5, why $100-$300 box to go from TV to VGA, why not a simple RCA to Dsub15 cable adapter?
I wanted electronic reasons, didn't really get any good reasons, until after I accepted that question, and then PCBONEZ came with exactly what I was looking for. I put his info in here because this is a subject that has never been answered anywhere I can find, and is a question needing a good hardware answer.
Anyone may contribute to this question, but please stick to electronics, please. I leave it open longer this time, but PCBONEZ, I would also like you to add any other thoughts on electronics, vs. cost. Thank you all.
I wanted electronic reasons, didn't really get any good reasons, until after I accepted that question, and then PCBONEZ came with exactly what I was looking for. I put his info in here because this is a subject that has never been answered anywhere I can find, and is a question needing a good hardware answer.
Anyone may contribute to this question, but please stick to electronics, please. I leave it open longer this time, but PCBONEZ, I would also like you to add any other thoughts on electronics, vs. cost. Thank you all.
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ASKER
Simply find out why a VGA->TV adapter can be made for $5, but a TV->VGA adapter is a box that costs typically $100 up to $300. That is all. I want to run a cable signal in, directly to a VGA (instead of TV), without an expensive box. Sound is not the issue, the signal conversion is the issue, why is it so hard one way, but so "trivial" (i.e. $5) the other way? Is it just volume Mfg, or is there a valid reason for it?
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It would be more proper to replace the term "TV" with "RF" in most of this discussion.
We are talking about "VGA signals" vs "RF signals" and not directly about monitors and TV's.
We are talking about "VGA signals" vs "RF signals" and not directly about monitors and TV's.
I've looked at the link to the e-bay cable that you provided in your initial question as prove that VGA to composite video is indeed just a cable..
My question is, have you looked at the disclaimers in the ebay ad? :
- It will work with laptops and desktops with VGA cards that has TV-Out function capability through the VGA connector
- Please check your PC & Video Card manual or manufacturer to make sure that your VGA card has TV-Out function capability through the VGA connector to ensure this cable will work for you,Otherwise the cable will not function
- We are not responsible for compatibility Issue
If you review the VGA connector pin layout then you will see the following:
1 RED
2 GREEN
3 BLUE
4 ID2
5 GND
6 RED SHIELD
7 GREEN SHIELD
8 BLUE SHIELD
9 NC
10 SYNC RTN
11 ID0
12 ID1 or DDC DATA
13 HSYNC
14 VSYNC
15 ID3 or DDC CLOCK
As you can see, there is no "TV-Out" signal in the VGA connector... Have you actually seen this working?
My question is, have you looked at the disclaimers in the ebay ad? :
- It will work with laptops and desktops with VGA cards that has TV-Out function capability through the VGA connector
- Please check your PC & Video Card manual or manufacturer to make sure that your VGA card has TV-Out function capability through the VGA connector to ensure this cable will work for you,Otherwise the cable will not function
- We are not responsible for compatibility Issue
If you review the VGA connector pin layout then you will see the following:
1 RED
2 GREEN
3 BLUE
4 ID2
5 GND
6 RED SHIELD
7 GREEN SHIELD
8 BLUE SHIELD
9 NC
10 SYNC RTN
11 ID0
12 ID1 or DDC DATA
13 HSYNC
14 VSYNC
15 ID3 or DDC CLOCK
As you can see, there is no "TV-Out" signal in the VGA connector... Have you actually seen this working?
I just checked out your other post and the "cable" you are talking about. hfern is correct. The cable is just a DB-15 to RCA/S-Video converter. It converts nothing. Your PC must be able to do TV-Out signals through the VGA connector, which means the "brains" to convert from VGA to TV are supposed to be includeded in the PC, which is the expensive part.
If you were to get this cable and connect it to a "normal" VGA card it would not work.
It would be like having a T.V. antenna, getting 300 Ohm T.V. antenna to coax converter, connecting it to your T.V. and expecting to get cable channels.
If you were to get this cable and connect it to a "normal" VGA card it would not work.
It would be like having a T.V. antenna, getting 300 Ohm T.V. antenna to coax converter, connecting it to your T.V. and expecting to get cable channels.
ASKER
I think PCBONEZ and giltjr hit on the real guts of this question, best said by PCBONEZ -- the TV conversion requires a tuner, and that is the most expensive part of all, not just to convert the signal, but to tune and convert many signals in a logically organized (useful) fashion.
Therefore one cannot compare a ready made signal, coming out of a VGA, to the complex raw, multi-frequency-stacked signals coming out of a cable wire. Therefore it would have to cost at least 10x what a simple VGA>TV adapter does, and finally I now agree that the TV->VGA conversion must cost more because of the complexity in decoding the signalS (emphasis on plurals).
I knew what the EBay cable does, and you might be interested to know I found a TV-VGA tuner box on ebay for about $48, so we will see if it is any good. This was not just an academic question, it had real practical value, and I thank everyone for contributing. Bye !
Therefore one cannot compare a ready made signal, coming out of a VGA, to the complex raw, multi-frequency-stacked signals coming out of a cable wire. Therefore it would have to cost at least 10x what a simple VGA>TV adapter does, and finally I now agree that the TV->VGA conversion must cost more because of the complexity in decoding the signalS (emphasis on plurals).
I knew what the EBay cable does, and you might be interested to know I found a TV-VGA tuner box on ebay for about $48, so we will see if it is any good. This was not just an academic question, it had real practical value, and I thank everyone for contributing. Bye !
I think you got it.
Something else to reflect on.
If of about the same screen size,
,,, a TV costs more than a monitor, ,,, Because it has all those tuning parts in it...
Something else to reflect on.
If of about the same screen size,
,,, a TV costs more than a monitor, ,,, Because it has all those tuning parts in it...
ASKER
Not really, 21" CRT used to cost 5X a TV, only now everyone wants TFT are they cheap. I have oodles of extra 21" monitors too, want to put them to use, not buy TV until high definition cost less than $100. HA!
Well, the problem with the cost of a T.V. vs. display monitor is capabilities. Although the display monitor does not have the same type of brains as a T.C. it can handle much high resolution and scanning frequencies.
I beleive that T.V. resolutions (NTSC) is about 720x480 at about 60 Hz refresh. A display monitor can go well above that resolution and refresh rate.
Once you get into the L.C.D display and T.V. you are basially talking about the cost to add a T.V. tuner to the display.
I beleive that T.V. resolutions (NTSC) is about 720x480 at about 60 Hz refresh. A display monitor can go well above that resolution and refresh rate.
Once you get into the L.C.D display and T.V. you are basially talking about the cost to add a T.V. tuner to the display.
ASKER
Brief technical explaination. (Basic)
Modulation = Superimposing a signal over a carrier frequency.
VGA signal to TV.
All that's needed is to modulate the signal into RF.
Only one frequency needs supported by the converter.
The TV's tuner does the rest.
TV signal to VGA.
You need a tuner/demodulator.
Many frequencies must be supported. (Unless you only want one channel.)
More parts = more money.
Input to tuner is not one signal, it's a whole bunch of signals mixed together.
The signal goes into the tuner which strips out all the unwanted frequencies leaving just the desired one. (Channel)
Then it goes through a demodulator that strips out the carrier frequency leaving just the video signal.
That's much more complicated than taking a video signal and modulating it into one RF signal.
It shouldn't cost much more.
~~ IF you only want ONE channel.
Nobody's gonna make one like that 'cause who'd buy a TV tuner to VGA gadget that could only do one channel????
.
TV to VGA means converting an RF signal into a video signal. -video signal out-
VGA to TV means converting a video signal into RF. -RF out-
In your Satellite TV example the all you are doing is using two tuners instead of one.
The output of the Satillite tuner to the TV is one channel of -RF-.
It's not a video signal.
The example is closer to the $5 adapter you mentioned in the initial question because the output is RF.
A tuner is basically just an adjustable frequency filter.
They are expensive relative to other parts because they have to handle many frequenices.
If you have a set frequency (one channel) then the other componets you would need are.
An RF amplifier (makes the RF signal large enough for the demodulator).
-- This could be simpler 'than normal' RF amp because it only needs to pass one frequency.
The demodulator (strips the carrier signal out)
-- This could be simpler 'than normal' demodulator because it only needs to handle one frequency.
A signal amps for sound and video (boosts the output of the demodulator to usable levels.)
Video driver circuit (to convert the signal to a VGA output.)
Audio driver circuit (to convert the sound to a speaker output.)
Probably an audio amp unless the speakers are amplified.
Forgot about sound, din' ya??