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ccs_hello
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Reged: 07/03/04
Posts: 5224
Analog Video Technology (Part 1)
      #2040557 - 12/10/07 12:18 AM

Analog Video Technology (Part 1)

[Note: some descriptions are US-centric]

1.0 Video Engineering

Analog Video is an established trade from the video broadcasting industry with many standards, practices, and established methods.

Multiple analog signal processing and analog signal transmission stages take place from
the beginning of incident light to electronic signal conversion (image area sensor) all the way
down to the final electronic signal to 2-dimensional photo display unit (i.e., video monitor) conversion.
Overall, there are many intended signal manipulations as well as unavoidable signal distortion,

especially when signal is in analog domain.

The degradation, be it in loss of spatial resolution*1, e.g., TV lines (can be measured in both H and V

directions), or introduction of additional noise causing lowering S/N ratio, are rather undesirable.

*1 not just caused by S/N loss, but also by processsing, e.g., down-sampling/scaling, compression, etc.


2.0 Video System End-to-End View

2.1 Video Acquisition

- Image Sensor:
most frequently used are CCD area sensors
1-chip color sensor has Bayer/color-mosaic filter overlay


- video camera front-end:
charge to voltage tranform using correlated double sampling (CDS),
Processing, gamma correction, color-space conversion,

- video camera formatter:
Baseband Encoding: H-blanking, V-blanking, Y/C coding, Black-pedestal, composite CVBS video encoding


2.2 Video Transmission

(if needed,)
over the air Analog TV broadcasting: Vestigial SideBand analog RF modulation in VHF or UHF TV bands
Over the air Digital TV broadcasting: 8-VSB modulation in ATSC
Over the cable Digital TV broadcasting: 64 QAM modulation

Direct analog cable link
- composite (CVBS) video RS-170A cable (one RCA jack)
- S-Video Cable (Separate Y:Luminance and C:Chrominance channels)
- Component Cable: Y Cb Cr channels (3 RCA plugs)
- DVI-analog (sibling of component format)

Optional Video Proc Amp is used in-line during analog transmission for signal amplification and adjustment

Digital cable link: E.g., CCIR601, scaled DV, 1394 (firewire), DVI-digital, HDMI, USB isochronous pipe, etc.


2.3 Video Reception and Decoding

Baseband Decoding: CVBS separation

Color-space conv


2.4 Visual Display Device Technology

- CRT
- TFT LCD
- Plasma
- DLP

====================================

To be continued.

Clear Skies!

ccs_hello


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ccs_hello
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Re: Analog Video Technology (Part 2) new [Re: ccs_hello]
      #2047556 - 12/13/07 12:51 AM

Analog Video Technology (Part 2)

I'd like to mention a caveat: analog video specification, even in the written form, especially in consumer video space, tends to be "market driven". It is up to the end users to read thru the smoke screen.


3. Video Quality

There are multiple parameters measured in the video quality area,
since most astro-video observation are slow updating/non-moving events (and definitely non-sport/fast-action events), the temporal resolution is less important.
However, spatial resolution is still very important.

S/N ratio drops when multiple cascaded analog signal processing elements take place.
One can relate this to repeated analog VHS tape recording/editing.
After multiple generations (about 3) of recording/editing, the resulted video simply looks
terrible and like all washed-out images.

These can be viewed as dB loss as analog signal chain starting from a high grade CCD sensor offering a 65~70 dB S/N, 50~55 dB monochrome camera (46~50 dB color camera) baseband video output, until the final display only showing a 45 dB (40dB color) or so quality video.

The quality reduction in each of these multiple stages sometimes are using a rather loose term: Kell factor/Extended-Kell factor. People tends to use their own figures and somewhat related to technology used. I choose not to use that "polluted" term. But I'll introduce my estimated numbers for individual stages.

One popular measurement method is to express the static image's resolution by TV-Lines (TVL).
TVL can be Horizonal TVL resolution and Vertical TVL resolution.
Since analog video formats (e.g., NTSC and PAL) have fixed number of rows of scan lines and these scan lines are just low-frequency signals, the TVL-V figure does not vary a lot (assuming perfectly de-interlaced.)
However, TVL-H does vary a lot and does degrade as more stages of analog processing take place.

One can relate the TVL figure as individual pixels one can visually count.
Also the term: each line pair (LP) represent two TV Lines.
E.g., NTSC has about 460 active/viewable herizonal scan lines per frame (2 fields).
If all odd lines are all black and all even lines are white, one can count there are 230 LPs or 460 TVL-V (460 rows). One can even note there are 460 pixels if counted from top to bottom.


3.1 Proper Usage of Video Quality

Rule 1:
It doesn't pay to use a super high grade display device to show a low quality video source in the first place. It won't magically invent the quality which does not exist from the thin air.

Rule 2:
It doesn't make sense to use a (super) restrictive signal processing/signal delivery element to "choke" the video quality, if the original signal source's quality is good and the display device's quality is also good. Few examples:
- high compression ratio codec in the middle to save the bandwidth
- analog recorder to store then later play back (remember the previous VHS recorder story)
- low quality wireless transmitter
- mpeg compression based transmitter/receiver system

Rule 3:
If there is no need to have a high quality (in this case, high reolution) display due to:
- display area is small (portability, battery power, etc. reasons)
- cost considerations
There would be little reason to get the high-end CCD cameras or high-grade signal delivery system.
I.e., you won't tell the difference anyway.



4. CCD Camera Resolution

Set aside the proprietary Advanced HAD format CCD (typically type-1/6" used in camcoders), CCD used in EIS (Electronic Image Stablization, typically using selectable ROI windowing, i.e., gyro-driven/moving "image frame of interest" technology) camcoders, and some still-high-resolution-image capture camcoders, the CCDs of astro-video interest are coming from security/surveilance camera industry.

Let's temporarilly skip the one-shot color (Bayer array) CCD but use the simple monochrome CCD as example for now.
Typically standard resolution (510*494) or high-resolution (768*494) CCDs are of interest here.
Same/similar CCDs are also used in digital camera-head (need PC for processing) such as the DSI family.
If using digital method, individual pixel values are transfered as is. E.g., DSI Pro's monochrome CCD resolution is 510*492. Thus captured image in PC's will have 510*492 resoluton.

But if a similar standard format CCD is used in analog video camera, the TVL-H are need to multiply by 0.75. In the above example, the monochrome camera will be rated as 380 TVL (H). (510 * .75 approx)
The high resolution CCD will be rated as 570 TVL.

For one-shot color CCDs, in digital version of implementation, for reolution, it has to be derated. But it will not be as low as analog processing for few reasons:
- the starting resolution from individual pixel is one-for-one, so it will start from a better starting ground.
- since de-Bayer is processed by PC, premium algorithm can be used, as oppose to simple add/substraction method used in analog video camera.

For a standard format compementary-color Bayer CCD used in analog video camera, the TVL-H are need to multiply by 0.61 (or 0.64 just a personal taste). In the above example, the color camera will be rated as 330 TVL (H). (510 * .62 approx)
The high resolution CCD will be rated as 470 TVL.
In anorther word, de-rate the one-shot color to about 80% of the monochrome CCD resolution.

Note: these number can be measured by taking the picture of a resolution chart.
E.g., http://www.bealecorner.com/trv900/respat/EIA1956.pdf is a resolution chart/test target.
Usage: Print a nice copy then point your camera at that fully illuminated chart and make sure it fills the whole video frame. Now inspect at which number the lines begin merged and non-distinguishable.

=====================================

To be continued.

Please do not go out immediately to buy the best of best device just because you read section 3 and 4 of this article. There are other factors to be considered which I'll try to cover soon.

Clear Skies!

ccs_hello


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ccs_hello
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Re: Analog Video Technology (Part 3) new [Re: ccs_hello]
      #2054059 - 12/16/07 02:02 AM Attachment (97 downloads)

Analog Video Technology (Part 3)
Analog Video Technology: transmission and distribution system

Before discussing the topic: transmission and distribution system, I'd like to make additonal comments on resolution described in part 2:
It is typical only describing resolution in monochrome term and one will find many resolution charts are in B&W. Color resolution in consumer video domain tends be lower, e.g., 1/4th of the B&W resolution, for bandwisth saving and no need to provide extra resolution human visual system won't perceive the difference anyway.

P.S., any one measured their astrocam, please let CNers know the resolution measured (method described in part 2 article.)

Also note there are other attributes on video quality than just spatial resolution. One area is the bit-depth, i.e., the dynamic range of the displayed picture. If insuficient bit-depth, posterization will become more pronounced.

Now back to our normal program :


5.1 Digital Baseband

Using high bit-rate digital format for transmission is the top-end method of maintaining the video quality. E.g., CCIR601 (studio grade, short distance transport using parallel bus), DigitalVideo (scaled down and some compression applied), 1394 (firewire): another way of sending DV, DVI-digital, HDMI: similar to DVI with other "features", USB isochronous pipe: basically high speed streaming, etc.

5.2 Analog Baseband

In analog format, the most popular format is:
- Composite (Color-Video-Blank-Sync, i.e., CVBS) video,
which is using one cable either a professional RG-59 coaxial cable with BNC connectors or thinner cable with RCA plug (phono plug) on each end. The signal riding on the composite cable is a multiplexed Y (Luminance or Luma) and C (Chrominance or Chroma) format, C is the subcarrier of the composite signal. Special care was made to reeduce the cross-modulation, interference, and other artifacts. The standard is RS-170A as the baseband format in the broadcasting/cable industries.
There are bandwidth and spectrum restrictions on such format since spectrum usage is allocated and licensed while audio interference should also be avoided. Typically, about 4.2MHz is used for RS-170A.

This translates to 330 TVL (80 TVL per MHz approx.)
When such format is used in local composite video signal distribution, the bandwidth upper limited can be higher. Approx. 500 TVL is possible but will require serious Y/C signal separation and now C signal has much higher possibility to cross-interference with Y signal.

- There is a legacy composite (VBS) video format: RS-170 which was used pre-1953 when TV system was just a B&W system. It has a major advantage when used with B&W video cameras (popular in Astro applications). We'll discuss this subject at the end of this article.

- To address the weakness of the mixing of Y/C signal in one baseband composite video format, a new Y/C cable (commonly known and accepted to be called S-Video Cable) is developed. The S-video cable carries Y and C signals separately. In general, if the video source (color camera) and the display device (video monitor) both have S-Video output and input, use of the S-Video cable is preferred. I.e., combining Y/C and properly separating Y/C is hard. Using S-video cable would avoid this task.

- Further technology improvement is driving a new format: Component video format where three singals: Y Cb Cr are riding on 3 separate cables (each using RCA plugs with G, B, and R color code.)
The video refresh rate can be different, e.g., used in HDTV or progressive mode video) and the C (Chrominance) signal's interal 2-Dimension vectors are now transported separately as Cb and Cr signals.

- DVI-analog format is a sibling of component video format, where the same analog signals are riding on a different cable and using the DVI connector.

5.3 Broadcast Video Signal

over the air Analog TV broadcasting: Vestigal SideBand modulation in VHF or UHF TV bands.
The available bandwidth limit the resolution to about 330 TVL.

Over the air Digital TV broadcasting: 8-VSB modulation
Over the cable TV system Digital TV broadcasting: 64 QAM modulation


Some very low end wireless transmission system may overly compress the signal such that quality may be very poor.


5.4 Optional Video Proc Amp
When baseband transmission distance is long and high-grade coexial cable is not used, video distribution amplifier or proc amp may be used in-line for signal amplification and video adjustment.


5.5 RS-170 monochrome format

RS-170 standard was use in the original B&W NTSC signal format. There is no color signal at all. In most of the color video monitors, there are Y/C separation circuit for handling composite color signals. Such circuitry degrade signal quality and clamp the andwidth usage. This is the reason I mentioned, if using a color camera, use S-Video cable as much as possible.

Per RS-170A (color NTSC) standard, even the video program source is B&W (old TV recorded programs or B&W movies) program, the transmitted signal will still have "color-burst"*1 embedded in there.

*1 Just for simplicity, please view color burst is a flag to tell the video monitor the transmitted program is using post-1953 (NTSC color) technology.

RS-170 signal has no color burst in there. Most (about 99%) of the modern video monitor can handle RS-170 signal input and properly display the video as B&W. In that mode, any Y/C separator caused limitation (e.g., bandwidth filtering restriction) may be removed. This is triggered by lack of color-burst flag information.

Some professional monitors may even have the "color killer" mode which will make the video monitor only handling the Y part of the signal and Y/C separation restriction removed.

P.S., In one sample of the monochrome video camera, I notice it outputs RS-170 signal. This is very vendor/model specific.

A proper implemented (Y/C cable) S-video output video device, the color-burst should*2 only exist in C signal channel.

*2 I found at least one brand/model of video device, in addition to C-channel, the Y-channel still has the color-burst. This is an incorrect implementation.

My previous description is the lead-in to explain the reasons and background of makeing RS-170A signal looks like a RS-170 signal, especially when video monitor does not have the "color killer" feature and video source cannot be set to putput RS-170 only.

The prerequisite is the video source has the S-Video outout (and does not have the bug as described in footnote *2).

Method 1: cut the (Y/C cable) S-video cable's "C" lead or just cut the "C" cable
Method 2: use a special S-Video to composite video adapter (inside is just taking the S-video's Y signal out to the RCA plug)

Hope this can help for the B&W camera owners to squeeze a little bit more TVLines.

==========================

Next part: video monitors

Clear Skies!

ccs_hello

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ccs_hello
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Re: Analog Video Technology (Part 4) new [Re: ccs_hello]
      #2069119 - 12/23/07 01:15 AM Attachment (112 downloads)

Analog Video Technology (Part 4)

Display Technology - section 1

Before the deep dive, let's discuss some fundamentals:

a) Consumer electronics is typically very competitive. The initial phase of the product has to win a major market share/brand&model recogniztion (hopefully high quality and low price tag), then reduce the cost and sell it in a large volume. This is the reason why "do your homework" and tracking the product's current state (hopefully by not-tinted end-users' opinions) is very important. For hungry manufacturers/distributors, it's understandable what they have to do ...
I strongly suggest we do not quote those glossy' numbers/features unless these are proven facts.
(Too busy picking up my jaw on the floor... )

b) There are "brand-only" products, i.e., company sold the "name" to others.

c) Even the device came from a known brand, model X does not necessarily have a good correlation with model Y, checking with the specifics is important. In few cases, even with the same model number, different versions/generations may give surprises.

d) CRT displays, by trade, always have to deduct 1" from its stated diagonal size. LCD displays usually do not.

e) From the tradition 4:3 display format (thinking it is 12-wide : 9-height is more helpful for calculation) evolving into 16:9 HDTV (or called "wide") format, there are few interesting points:

- Wide screen has 4 extra unit width-wise, two units on the left and two on the right (16 in Wide vs. 12 in std)

- since diagonal is still the measurement method for display size, one may find 8.5" Wide LCD is about the same as 7" standard LCD display, if you display the NTSC (4:3) format as is, i.e., not let the monitor stretch automatically in horizontal direction to fill the entire screen (unless you really like fat face )
example 2, a 22" wide would show the same area as 18" std display, if not horizontally stretched
example 3, a 7" wide would show the same area as 5.6" std display, if not horizontally stretched
[Hint: you might want to check the recent pricing premium over "just few inches" bigger (but really it's just wider) monitor ]

f) Experienced users and manufacturers know: monitor's adjustment knobs disappeared long ago for reliability/maintenance/cost reasons. Usability does not always track well with reliability.

Now back to our normal program ...

=========================================================

6.1 Immersion, Resolution, and Viewing Distance

The commonly asked question is what size monitor is the right size. There are two different ways to answer it:

- what type of viewing distance works the best for you (this probably is the primary constraint)
(close inspecting or sit back and relax)

- It turns out that optimizing the best angular resolution (i.e., see the picture sharp and clear) with the spatial resolution of the intended "system" need provide will give a range (min. and max.) of acceptable viewing distance. Too close, will see the scan lines and actual pixels. Too far away, picture looks fuzzy. Looking close but not shorter than the minimum distance will have wider FoV, giving the sense of more immersion. This is one reason certain organization's recommendation on viewing distance tend to be on the short end, since they are known for "better (immersion) experience".

Please note I did not say it's just the monitor resolution which counts, but the overall "system". For example, if a high quality 500 TVL monitor is used to display a video signal which only has a 280 TVL resolution, then use the 280 TVL number, since close-inspection of the monitor will not be able to show anything greater than 280 TVL, but will only let you down since the fuzziness of the 280 TVL video are now seen as "watercolor-like" very clearly. I.e., 500 TVL monitor will not be able to invent a beautiful picture in which it does not have in the first place.

The following is the commonly used viewing distance guideline, based on monitor size.

(NTSC resolution) 480i system 5:1 up to 10:1 (5 to 10 times the monitor height)

(HDTV-like resolution) 1080p system 2:1 up to 4:1 (2 to 4 times).
Note two times distance is awfully close, presuming the video it's displaying came from a high-quality HD source.

If a regular noisy broadcast SD (standard definition) program or a VHS tape is played and displayed on that HDTV arrangement with close-distance viewing, one will definitely regret setting the distance too short .

One might also notice that computer monitor (especially for XGA resolution or higher) viewing distance is quite short, if viewing text (like reading this forum post). But it is possible to view a movie (especially on a low quality YouTube movie) from quite a distance away.

In general, 30 degrees FoV is the maximum recommended value, e.g., large screen/home theater HDTV.
While for NTSC (SDTV), 15 degrees FoV is normal. If you note in the potpourri section on eye's FoV is about 120 degrees, you'll notice the surrounding beyond the TV set will be a distraction. I.e., not much an immersion experience.

Let's say NTSC-color has 330 TVL and has 15 degrees FoV. If a 4" LCD monitor (3.6" width and 2.4" height) is used to display a 330 TVL quality video, the viewing distance should be about 12".
We can say for 470 TVL higher-quality NTSC 4:3 aspect ratio video on the same monitor will be about 8.5".

Also note for the same 330 TVL but 8" LCD display, the viewing distance is doubled. But you may notice the light output has to about 4-times brighter and can cause greater light distraction (or L.P.).

Please note a lot of these are subjective.

(To be continued)

In later sections:
- Some key LCD monitor attributes (response time, contrast, illumination, viewing angle, etc.) and how to tell
- example of LCD display devices
- resolution of the monitors and how to measure them


===========================================================================


===========================================================================

Attached picture
(test resolution display on a $20 5" CRT B&W TV
note the last region is washed out)
signal source: a professional Tektronix test signal generator
multiburst patterns: 0.5MHz (3 white+3 black strips), 1, 2, 3, 3.58, and 4.2 MHz.

Detailed explanation will follow.


Clear Skies!

ccs_hello

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greg
scholastic sledgehammer


Reged: 01/25/05
Posts: 863
Loc: Central Ca.
Re: Analog Video Technology (Part 4) new [Re: ccs_hello]
      #2070675 - 12/23/07 11:02 PM

Quote:

Analog Video Technology (Part 4)

Display Technology - section 1

Before the deep dive, let's discuss some fundamentals:

a) Consumer electronics is typically very competitive. The initial phase of the product has to win a major market share/brand&model recogniztion (hopefully high quality and low price tag), then reduce the cost and sell it in a large volume. This is the reason why "do your homework" and tracking the product's current state (hopefully by not-tinted end-users' opinions) is very important. For hungry manufacturers/distributors, it's understandable what they have to do ...
I strongly suggest we do not quote those glossy' numbers/features unless these are proven facts.
(Too busy picking up my jaw on the floor... )

b) There are "brand-only" products, i.e., company sold the "name" to others.

c) Even the device came from a known brand, model X does not necessarily have a good correlation with model Y, checking with the specifics is important. In few cases, even with the same model number, different versions/generations may give surprises.

d) CRT displays, by trade, always have to deduct 1" from its stated diagonal size. LCD displays usually do not.

e) From the tradition 4:3 display format (thinking its is 12-wide : 9-height is more helpful for calculation) evolving into 16:9 HDTV (or called "wide") format, there are few interesting points:

- Wide screen has 4 extra unit width-wise, two units on the left and two on the right (16 in Wide vs. 12 in std)

- since diagonal is still the measurement method for display size, one may find 8.5" Wide LCD is about the same as 7" standard LCD display, if you display the NTSC (4:3) format as is, i.e., not let the monitor stretch automatically in horizontal direction to fill the entire screen (unless you really like fat face )
example 2, a 22" wide would show the same area as 18" std display, if not horizontally stretched
example 3, a 7" wide would show the same area as 5.6" std display, if not horizontally stretched
[Hint: you might want to check the recent pricing premium over just "only inches" bigger (but really it's just wider) monitor ]

f) Experienced users and manufacturers know: monitor's adjustment knobs disappeared long ago for reliability/maintenance/cost reasons. Usability does not always track well with reliability.

Now back to our normal program ...

=========================================================

6.1 Immersion, Resolution, and Viewing Distance

The commonly asked question is what size monitor is the right size. There are two different ways to answer it:

- what type of viewing distance works the best for you (this probably is the primary constraint)
(close inspecting or sit back and relax)

- It turns out that optimizing the best angular resolution (i.e., see the picture sharp and clear) with the spatial resolution of the intended "system" need provide will give a range (min. and max.) of acceptable viewing distance. Too close, will see the scan lines and actual pixels. Too far away, picture looks fuzzy. Looking close but not shorter than the minimum distance will have wider FoV, giving the sense of more immersion. This is one reason certain organization's recommendation on viewing distance tend to be on the short end, since they are known for "better (immersion) experience".

Please note I did not say it's just the monitor resolution which counts, but the overall "system". For example, if a high quality 500 TVL monitor is used to display a video signal which only has a 280 TVL resolution, then use the 280 TVL number, since close-inspection of the monitor will not be able to show anything greater than 280 TVL, but will only let you down since the fuzziness of the 280 TVL video are now seen as "watercolor-like" very clearly. I.e., 500 TVL monitor will not be able to invent a beautiful picture in which it does not have in the first place.

The following is the commonly used viewing distance guideline, based on monitor size.

(NTSC resolution) 480i system 5:1 up to 10:1 (5 to 10 times the monitor height)

(HDTV-like resolution) 1080p system 2:1 up to 4:1 (2 to 4 times).
Note two times distance is awfully close, presuming the video it's displaying came from a high-quality HD source.

If a regular noisy broadcast SD (standard defiition) program or a VHS tape is played and displayed on that HDTV arrangement with close-distance viewing, one will definitely regret setting the distance too short .

One might also notice that computer monitor (especially for XGA resolution or higher) viewing distance is quite short, if viewing text (like reading this forum post). But it is possible to view a movie (especially on a low quality YouTube movie) from quite a distance away.

In general, 30 degrees FoV is the maximum recommended value, e.g., large screen/home theater HDTV.
While for NTSC (SDTV), 15 degrees FoV is normal. If you note in the potpourri section on eye's FoV is about 120 degrees, you'll notice the surrounding beyond the TV set will be a distraction. I.e., not much an immersion experience.

Let's say NTSC-color has 330 TVL and has 15 degrees FoV. If a 4" LCD monitor (3.6" width and 2.4" height) is used to display a 330 TVL quality video, the viewing distance should be about 12".
We can say for 470 TVL higher-quality NTSC 4:3 aspect ratio video on the same monitor will be about 8.5".

Also note for the same 330 TVL but 8" LCD display, the viewing distance doubled. But you may notice the light output has to brighter and can cause greater light distraction (or L.P.).

Please note a lot of these are subjective.

(To be continued)

In later sections:
- Some key LCD monitor attributes (response time, contrast, illumination, viewing angle, etc.) and how to tell
- example of LCD display devices
- resolution of the monitors and how to measure them


===========================================================================

Potpourri:

About Human Eye:
Spatial Resolution: in well lighted situation, it's about 8000*8000 (sharper in central region)
FoV is about 120 degrees
Dynamic range in a dark adapted environment: 20 stops (Wow!! Amazing )

===========================================================================

Attached picture
(test resolution display on a $20 5" CRT B&W TV
note the last region is washed out)
signal source: a professional test signal generator
patterns: 0.5MHz (3 white+3 black strips), 1, 2, 3, 3.58, and 4MHz.

Detailed explanation will follow soon.


Clear Skies!

ccs_hello




Man that's a lot of words... I didn't really understand very much of it so I'm not sure if I'm better or worse off having read it all...

So I ordered a 9" 500 line color CRT Security Monitor... In just a few Simple words do you think it will produce a nice image from a MallinCam Color HYPER Plus using good cables?


Greg

--------------------
Gravity is like a magnet to Humans...4 yr Old Marcus Gregory Allen W.
Not tonight honey I have a Telescope... Greg W.
GEM SiTech Servo Goto
Home Built 14.5" F 3.3 MallinCam Newtonian
Building a 12" F/3 MallinCam Newtonian
Celestron 102mm F/5 Refractors
Orion StarShoot Pro Color
Sac-10
MallinCam Color Hyper Plus
9" Speco High Res. Color CRT Monitor
10' Home Dome
MallinCam Deep Space Observatory
Light polluted Backyard
Great Darksite 1.5 Hrs. Away


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smokin oakum
Carpal Tunnel


Reged: 09/24/07
Posts: 1529
Loc: Wilmington, NC
Re: Analog Video Technology (Part 4) new [Re: greg]
      #2070685 - 12/23/07 11:08 PM

I think so!!! I made the same decision after reading this post.

--------------------
Broadcasting live views of the night sky @
Sparkcast
C11 CGE / Hyperstar
MallinCam Hyper Plus Color
Orion 12" XTi f/4.9
MoonLite Focuser
Round Table Platform
12" Parralax rings

Cape Fear Astronomy Club




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ccs_hello
Postmaster


Reged: 07/03/04
Posts: 5224
Re: Analog Video Technology (Part 4) new [Re: greg]
      #2070775 - 12/24/07 12:00 AM Attachment (108 downloads)

Greg,

MC is using a 768*494 (better than standard-resolution) CCD as its imaging sensor. Assuming it's a color version and S-video cable is used, in best case 470 TVL can be achieved. I suggest someone with that camera and a very good CRT monitor to use the measurement method (print out the resolution chart ...) I described then check the resolution achievable.

500 TVL type of display is very nice. Usually studio monitors used in a SDTV boardcast station would be 600 TVL (or even 800 TVL which is beyond CCIR601 and unnecessary) models. These are heavy and power hungry.

But if the camera and the transmission system combined together does not deliver such type of resolution, e.g., just 400 TVL (Horizontal), then many 400 TVL monitors will suffice.

BTW, mine is a SONY PVM-xxyzQ chromacity-correct/8MHz >600 TVL/super-fine pitch (0.25mm) Trinitron model (list $1,200, fleabay: 1/30 to 1/6th the list price, used.) It is very heavy (18 Kg approx.) and consumes a lot of energy (100W approx).
{Test picture attached.}

Clear Skies!

ccs_hello

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greg
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Re: Analog Video Technology (Part 4) new [Re: ccs_hello]
      #2071690 - 12/24/07 01:15 PM

Quote:

Greg,

MC is using a 768*494 (better than standard-resolution) CCD as its imaging sensor. Assuming it's a color version and S-video cable is used, in best case 470 TVL can be achieved. I suggest someone with that camera and a very good CRT monitor to use the measurement method (print out the resolution chart ...) I described then check the resolution achievable.

500 TVL type of display is very nice. Usually studio monitors used in a SDTV boardcast station would be 600 (or even 800) TVL models. These are heavy and power hungry.

But if the camera and the transmission system combined together does not deliver such type of resolution, e.g., just 400 TVL (Horizontal), then many 400 TVL monitors will suffice.

BTW, mine is a SONY PVM-xxyzQ chromacity-correct/8MHz >600 TVL/super-fine pitch (0.25mm) Trinitron model (list $1,200, fleabay: 1/30 to 1/6th the list price, used.) It is very heavy (18 Kg approx.) and consumes a lot of energy (100W approx).


Clear Skies!

ccs_hello




Thank you Very Much,
My camera is the Color HYPER Plus so the 9" 500 line Color Monitor should be a good match for the output of the camera. Now if I could only find out if my Monitor has even been shipped or not... They told me today that it may or may not have been drop shipped to me from the factory on Friday, but they can't find out until Wednsday because of the holiday... No tracking # to me means no shipment... I'll be Making another call on Wednsday.

Thanks again for helping me understand a little more about matching a camera to a monitor. If I understand correctly...(and that's a BIG if)... A person only needs a monitor that is capable of handling the output of the camera being used. Using the best cables for the application (S-Video) will reduce noise and help get the best image possible on the monitor. Using an up converter will not magically produce a high definition image if the camera only puts out 768*494 resolution.
I know this is over simplifying the subject, and is probably not 100% correct, but this is what I've come to understand on the subject of matching a camera to a monitor for the best live view.

Greg

--------------------
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Edited by greg (12/24/07 04:41 PM)


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ccs_hello
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Re: Analog Video Technology (Part 4) new [Re: ccs_hello]
      #2072472 - 12/24/07 09:41 PM

Need to add some references:

- Andrew Inglis, Video Engineering, McGraw Hill
- Benson/Whitaker, Television Engineering Handbook, McGraw Hill
- K.G.Jackson and G.B.Townsend, TV&Video Engineer's Reference Book, Butterworth Heinemann
- Keith Jack, Video Demystified, Hightext Publishing
- Clyde Herrick, Color Television Theory and Servicing, Reston Publishing
- and many other books, papers, articles, datasheet, databooks, (professional gear's) instruction manuals, ...

BTW, a good paper to read about human eye's spatial resolution (resolving power) and dynamic range:
http://www.clarkvision.com/imagedetail/eye-resolution.html

Happy Holidays and Clear Skies!

ccs_hello


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b1gred
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Re: Analog Video Technology (Part 4) new [Re: ccs_hello]
      #2072825 - 12/25/07 02:57 AM

Outstanding primer. I'm making it a "Sticky" at the top of the forum so it's an easy reference.

--------------------
"Dark Skies & Great Viewing"

RandyR / W0RDR
GPS 9.25 XLT/Sky Align /FeatherTouch
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Edited by RandyR (12/25/07 02:58 AM)


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rolandlinda3
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Re: Analog Video Technology (Part 4) new [Re: b1gred]
      #2073346 - 12/25/07 01:06 PM

I agree...but it's more than a primer...it's a primer plus lots of detail. Eventually, perhaps an extra post with a table of key contents that are linked to appropriate sections....or a summary...will greatly help those getting in to astro video. Roland

--------------------
Roland
Blog: www.rolandlinda3.wordpress.com
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ccs_hello
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Re: Analog Video Technology (Part 4a) new [Re: greg]
      #2073575 - 12/25/07 04:28 PM Attachment (87 downloads)

Quote:

...
Thanks again for helping me understand a little more about matching a camera to a monitor. If I understand correctly...(and that's a BIG if)... A person only needs a monitor that is capable of handling the output of the camera being used. Using the best cables for the application (S-Video) will reduce noise and help get the best image possible on the monitor. Using an up converter will not magically produce a high definition image if the camera only puts out 768*494 resolution.
I know this is over simplifying the subject, and is probably not 100% correct, but this is what I've come to understand on the subject of matching a camera to a monitor for the best live view.

Greg




Greg,

You grasped the concept quite well. Just one correction on it:
in analog video, there is no discrete CCD resolution. That CCD is considered as a high(er) resolution CCD thus can provide more TVL, e.g., 470 TVL. But it is still an analog signal, thus there is no easy way to mask off a hot pixel, for example.

While on the CCD topic, I feel we should not too much worry about the spatial resolution, e.g., a 1/2" CCD with 330 TVL resolution will still be much better than a (camcorder's) type-1/6" CCD's 470 TVL resolution. This brings up two important attributes for CCD to consider: sensitivity and noise.

Let's say with the same CCD technology and same generation of refinement, a manufacturer is making two type-1/2" complementary-color CCDs. The first one is a standard resolution 510*494 while the second one is a fine resolution 768*494 CCD. What will be the pro/con amongst these two?

- both of them will cover the same sky area, since they are both type-1/2" sized

- std resolution CCD will have less (horizontal) TVL count
i.e., fine-reso one will have better picture resolution

- One per pixel basis (e.g., compare the green pixel in std-reso with the green pixel in fine-reso., the std-reso CCD's individual photosite will be more sensitive (defined as gathering photon quicker), since it has a larger per-pixel photo-sensing area, i.e., larger pixel aperture

- Std reso CCD will have larger pixel well size, i.e., has potential to generate more "S" (signal) component in the S/N figure (since "N" (noise) tends to be noise-controlled within the same amount in the same generation of the CCDs).
So we know larger pixel one will have a better S/N ratio.

- For overall CCD sensitivity, will high pixel count with smaller photosite gather the same amount the photon such that the net will come out even?
The answer is NO, still less. To make a long story short (I will describe it in detail and the calculation in my "CCD Intro" series' chapter 12 or so, in Beginning Imaging forum), the design of adding more pixels (i.e., mega pixel race) eats up more valueable real estate space.

=========================================

Attached is a B&W test picture on an inexpensive 14" CRT TV/DVD combo unit. I won't even bother to describe its resolution. The source is a B&W multi-burst RS-170A (i.e., with color-burst flag) composite signal feeding the unit of interest. In Part 3, I mentioned about the Y/C separation and potential color decoding issue. This TV (using straight video in) gave a solid (bad) example on that !

Clear Skies!

ccs_hello

Attachment


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jayscheuerle
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Re: Analog Video Technology (Part 4a) new [Re: ccs_hello]
      #2079614 - 12/28/07 03:41 PM Attachment (100 downloads)

I found the article on image detail in the human eye interesting, but some of its calculations were severely flawed by applying the highest resolution that the eye can see across the entire FOV. There is a VERY small area where you can see the equivalent of around 600 dpi (I'd estimate less than a thumbs's width at arm's length). Get a hand's width away from this and you're probably under 25 dpi! A snapshot of your entire FOV is likely to have less information than a 4MB picture file, but 3MB of that is located in an area the size of a coaster.

Fortunately our eyes dart around like flies and we seldom notice this variation.

If you only stare at the yellow dot at the center of these images, you'll notice very little difference between this image and the one that follows it, even though the 2nd image falls off to a 1.3 pixel guassian blur.

Attachment

Edited by jayscheuerle (12/28/07 03:53 PM)


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jayscheuerle
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Re: Analog Video Technology (Part 4a) new [Re: jayscheuerle]
      #2079646 - 12/28/07 03:54 PM Attachment (87 downloads)

If this was an image that filled your entire FOV, it would get VERY blurry the further you went away.

Attachment

--------------------
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Re: Analog Video Technology (Part 5) new [Re: jayscheuerle]
      #2082528 - 12/30/07 12:57 AM

Analog Video Technology (Part 5)

Display Technology - section 2

Please note this writeup is done on end of year 2007. Technology evolves and the market "climate" changes.

7.1 Image Sampling

In display parameters, there are three similar "clocks" need clarification:
- high frequency "pixel clock": this reflects spatial resolution in horizontal direction (i.e., TVL-horizontal), which is the most frequently referred "resolution" benchmark

- lower frequency "horizontal clock": this reflects spatial resolution in vertical direction (i.e., TVL-vertical), which usually is "more structured (almost a fixed number) across multiple designs", since they all based on a similar technology.

- very low frequency "vertical clock": this reflects temporal resolution (i.e., how many frame updates
per second), which needs to be greater than 24 frames/second to give human perception of non discontinuous "moving" images, i.e., video or motion picture experiences.

7.2 LCD Panels

Let's continue on TFT (Thin Film Transistor, a form of active driven-pixel display) LCD monitor discussions.

LCD glass has its pixel structure permanately created on its glass surface. This is LCD's native rsolution.

For optimal spatial resolution, an image/video need to be mapped to LCD as a close discrete correlation as possible. If there is no 1:1 resolution mapping, a scaler module (a DSP function such as FIR filter) may be used as part of the display unit to scale the pixel up or pixel down to minimize aliasing or cause less moire patterns. The scaler may be applied just on horizontal direction, vertical direction, or both.

Proper pixel clock registration and mapping will ensure high(er) quality in horizontal direction.

7.2.1 Digital Panels
--A--
For monitors directly take in digital signal input, the pixel clock can be delived from the embedded/implied digital data format. This is the most direct and optimal method to avoid degradation.

This can cover both graphics and video sourced digital video.

7.2.2 Analog Graphical Panels
--B--
There is a pseudo pixel-clock mapping method commonly used in analog (VGA or DVI-A) LCD monitor used in computer field. Recent computer LCD analog monitors can do that. By pressing an "Auto Calibraton" button, the monitor will attempt to find from the incoming analog signal about the pixel clock rate and alignment. It is possible if computer is displaying a "window" background, which is graphical oriented.

7.2.3 Analog Video Display Panels
--C--
The third case is the pure analog video signal input to the monitor. Consumer grade analog video signal (i.e., video signal has no relationship to line-locked or sub-carrier locked derived pixel clock) is using a simple NTSC encoder which does not contain any structure that can help the LCD monitor to find the structure or registration. This concept is pertinent to a CCD/CMOS analog video camera video source. E.g., even if CCD has a 768*494 active pixel structure, the 768 pixels in per horizontal line just provides better horizontal resolution, but will not* be mapped into any type of CCD pixel to LCD pixel mapping, since NTSC video encoding destroys the structure (* exceptions do exist, but not the simple consumer-grade video any more). In this case, using TVL-horizontal makes better sense.

7.3 Effective Horizontal Resolution

A frequently quote degradation factor on --c-- mode of display, is to use (again, the pseudo term: Kell Factor) a "de-rating number" when used in compared with mode --A-- or mode --B--.
For example, if a LCD digital monitor (mode --A--) with a native resolution of 1280*1024, while the digital data feeding it is also 1280*1024 (i.e., 1:1 pixel mapping), the maximum TVL-H will be 1280 while the TVL-V is 1024! This will be a very impressive number, assuming the data source itself has such a quality. I.e., the constraint will most likely come from the information source, not the display.

Let's use another example, a digital LCD (mode --A--) with 640*480 native resolution, has the potential to handle 640 TVL-H sourced information, if pixel registration/alignement (data feed -> data display) is properly done. But if the same LCD glass is used as the base to build a mode --C-- analog video monitor, the Kell Factor kicks in. This is a fuzzy factor and is highly dependent on the niche technology being used (if you remember Faroudja Lab or Signetics-Philips ). This number has been from the old/classsic 0.7 in the CRT era to a number as high as 0.85 in a better grade design. So in this example, the analog LCD (mode --C--) can have 540 TVL-H, if optimal design. Actual measurement would be more accurate.

Another example, a LCD glass has a 480*240 resolution can have about 400 TVL-H resolution, if it has a better grade design. Again, actual measurement would be better/more accurate.

7.4 Vertical Resolution

For a LCD analog monitor, it may accept traditional SDTV (Standard Resolution TV, in US, it's NTSC signal known as 480i), but it may also accept other higher resolution formats such as 480p, 720p, 1080i, and 1080p**. Some LCDs also accept other format a computer VGA/SVGA/XGA/SXGA/WXGA/...
(** these numbers reflect vertical scan lines, not horizontal scan lines).

Please note in the previous paragraph, there are two "480" format: 480i and 480p. 480i means there are 480 horizontal scanline in the interlaced fashion, which is 240 odd-numbered lines in an odd field and 240 even-numbered lines in even field. Altogether there are still 480 lines, but due to interlaced scan, te vertical resolution has to be de-rated. Usually multiply by 0.7 is reasonable. In 480p, it is progressive scan, i.e., 480 lines displayed in one shot. 480p requires high-end de-interlace algorithms. In early days, these may also be called EDTV as a transitional format. Proper de-interlacing is hard. Occasionally, sone artifacts and discontinuity may be seen.

In LCD technology used in interlaced analog video, there are many monitors uses 240 scan lines (234 lines version is similar). E.g., the 480*240 LCD design given before. It is not desirable to display the odd lines (in odd field) and even lines (in even field) to the same LCD display positions (just 240 lines). There will be many artifacts (pixel crawling, frame jumping back-n-forth, etc.) If there is a fancy algorithm allowing such operation, please let me know. So (at this point) I claim such technology, only odd fields are used to be displayed (can swap "only odd fields" with "only even fields"). In another word, vertical resolution suffers, if the video source's verticle resolution is high. Good news for one-chip Bayer-array color CCD based video cameras, since the degradation isn't significant due to field-integration mode is used. Even better news is that for long exposure mode video cameras (e.g., many specialty cameras mentioned in this forum) only one "field-integration mode" formed image***, which only has 240 horizontal lines, is read after the long exposure. (***Explanation is in my CCD Intro article part 10.6 when done in field-integration mode).

7.5 Marketing's Special Definiton: pixel count

In consumer market, fierce competition drives the untrained users toward which model has a "large number". In an attempt to win market share, commonly known term, like pixel got a new meaning. Such new pseudo-definition sometimes even becomes the norm in a specific sector.
For display technology, a pixel position may be form by three color phosphers or three RGB colored sub-pixels. Subpixel is a recognized term. But some marketers want to call sub-pixels as pixels. It is 3 times inflation. In this series of article, we will use pixel for a B&W pixel (monochrome display) or a combined bundled of RGB sub-pixels.

7.6 Color Depth

LCD's individual B&W pixel or each R, G, or B sub-pixels has the bit depth, i.e., shade of grey/color. Most commonly seen LCD panel has either 4, 6, 8-bit depth, while 6 bit probably is the most common panel which really reflects the current technology.

7.7 Other LCD panel attibutes

There are many atributes in a LCD panel. Some of these parameters may not be so important or pronounced in a specific application. I would suggest the user understand the application(s)' characteristics then pick the most important attribute(s) for that application or applications, if multi-use.

For example, long exposure videocam (almost like a SSTV type of slow response) does not update the picture content very often. There is a parameter: response time which is the sum of the pixel turn-on time and the turn off time. (Some very creative guys just quote one number and conveniently forgot the other ). The response time can be very importnat for a fast-action sport event for HDTV viewing, but not so important at all for in-car GPS navigation. I have seen the number from a low 8mS (Tr + Tf) to a high 100mS range. For normal NTSC video, response time about 20mS or less is desirable. Higher than that figure, potential "comet tail" or "ghost image" may be perceived.

Attibute like contrast can be useful for high ambient light. It also gives the preceived picture "sharpness".

Another attribute: brightness sometimes got mixed with (backlight) illumination. These are supposed to be two independent adjustment and should not be combined into one. Under the dark night, a fully tunr-down brightness may not be "dim" at all. Bright backlight can leak through from multiple places.

Viewing angle is yet another interesing subject. If it's for a HDTV in your living room, wider viewing angle is nice. If it's for astrovideo viewing in a star party (non-outreach table), too wide the angle may be quite distracting.



===============================================

Next Article in LCD section:
- example of LCD display devices
- resolution of the monitors and how to measure them

Next subject: video/image capture and recording


Clear Skies!

ccs_hello


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ccs_hello
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Re: Analog Video Technology (Part 4a) new [Re: jayscheuerle]
      #2082542 - 12/30/07 01:06 AM

Jay,

Regarding eye's true resolution, be it 8000*8000 or 9000*9000 across the entire 120 degree FoV, may be a great question for OMD or someone who disect eyes to count rods and cones . I absolutely agree the center region is the sweetspot. Peripheral vision is always sub-optimal.

My point really is to illustrate the spatial resolution and dynamic range (after dark adapt) of a human eye is going to be hard to match by the current CCD/CMOS sensor technology.

One thing human visual system don't do while MCHC and friends can do is the long duration integration. Call that (deficiency???) a survival necessity .

Clear Skies!

ccs_hello


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ccs_hello
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Re: Analog Video Technology (Part 6) new [Re: ccs_hello]
      #2082924 - 12/30/07 09:30 AM Attachment (88 downloads)

Analog Video Technology (Part 6)

Display Technology - section 3

Please note this writeup is done on end of year 2007. Technology evolves and the market "climate" changes.

Also note that the actual pixel counts are approximate.
It is quite familiar that some "paddings" are phased in the calculation, not because of bad math.
Note: wide screen can be any aspect ratio different than 4:3. 16:9 or 5:3 are common ones.

=========================

It is very difficult to know the accurate pixel count of a LCD panel. I used a DSLR camera with macro lens to shoot the On-Screen Display (OSD) characters shown on the LCD. Then pixel-peeping the characters and compare the relative size to the whole LCD panel to guesstimate the pixel count.

The obtained number is the native resolution.
For analog LCD video monitor, we can use a 0.85 Kell factor for a good LCD video monitor or 0.7 for a "sorry" monitor as the multiplier.

The actual measurement can be done using the resolution chart. Standardized test patterns using professional video test instruments* would be nice.
(* these instruments output composite video signals; some can even send out S-video and/or component signals)

Resolution chart test (for TVL-horizontal).
The source is a professional test pattern generator and the pattern name is "multi-burst".

From Left to Right (skip the first)

0.5 MHz, 1 MHz, 2MHz, 3 MHz, 3.58 MHz, and 4.2 MHz
(use 80 TVL per MHz formula, we have:)

40, 80, 160, 240, 280, and 330 TVL.


I am experimenting using PC VGA card with TV-out to send out test signals. I am in the stage of test refinement.
See "work in progress CN post".

==================

Next subject: video/image capture and recording



Clear Skies!

ccs_hello

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ccs_hello
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Re: Analog Video Technology (Part 6a) new [Re: ccs_hello]
      #2082951 - 12/30/07 09:53 AM Attachment (109 downloads)

For the curious, you might ask which monitor I feel most useful/worthwhile? The answer is not my Sony CRT Studio grade video monitor, but this:



It is my el-cheapo PC LCD monitor with a twist!

It's a 17" 1280*1024 native resolution mode --B-- monitor.
But I used an inexpensive (I think it's $60 approx.) "TV Box" to convert video signal, i.e., mode --C-- signal (takes in 4 different formats: tuner, composite, S-video, or componet) into the monitor's VGA (HD15) connector format.
{edit}
Such converter sending out native LCD resolution would be optimal.

Clear Skies!

ccs_hello

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Edited by ccs_hello (12/30/07 11:20 PM)


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skyguy88
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Re: Analog Video Technology (Part 6a) new [Re: ccs_hello]
      #2083528 - 12/30/07 02:47 PM

Hi ccs,

Would you identify the "TV Box". Do you notice a difference betwee the s video and composit inputs? I've been thinking of getting a kworld 1680 (?) box to drive an LCD monitor (17 or 20in). And thanks so much for the analysis.

Bill McDonald

--------------------
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C8 on ASGT mount
Meade Starfinder 8N in on pedestal
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ccs_hello
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Re: Analog Video Technology (Part 6a) new [Re: skyguy88]
      #2083652 - 12/30/07 03:49 PM

Bill,

Mine is KWorld 1440 TV Box. For the test, I fed signal into its composite input but not noticed C-signal leakage into the Y-channel.
I have not yet noticed difference on composite vs. S-video. Probably I am not "exercising" it hard enough .

But I would not say that specific box is THE determining factor. I think the computer monitor resolution is the key factor. Its resolution is much, much better than a traditional LCD video monitor . This leaves a lot of headroom for the 'converter" box.

I have a hunch that the new winner is already here and it's cheap.
In the 2007 BF sale a month ago, there was a 19" Wide LCD HDTV on sale for $199 in C.C. (normal price $230-$270.) That device has an ATSC digital tuner, a NTSC tuner, composite/S-video/component/HDMI inputs, and computer VGA input. That is all-in-one contained within one LCD display. But I ran out the $ ...
Well, price will drop on these LCD monitors anyway.

Clear Skies!

ccs_hello


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