Strange question of the day: Why coax cable?

[Jeroen1000 0]

hi guys,

 

I know I'm new so my apologies if this is a moot or dumb question. I start out with the strangest questions first

 

Coax is essentialy a composite signal (includes both luminance and chrominance information and in case of regular TV also audio). I won't delve to deeply but sending this over 1 wire is asking for quality problems. Are there camera's which use Y/C (S-video, commenly called S-VHS) or YPbPr (component) or even RGB (also a component signal)?

 

It just doesn't make sense an expensive camera uses such an inferior video signal transport system. I suppose coax has plenty of bandwidth for B/W but when it comes to color it really is not the best choice. Any thoughts?

[scorpion 0]

If quality is of the essence then you would automatically switch to IP cameras with megapixal.

 

Why use an analog video with YPbPr or RGB when you can go digital?

[Jeroen1000 0]

Hi scorpion thanks for you reply. I'll provide more insight to my initial question now:

 

The reason for not purchasing a camera that digitises the signal is twofold:

 

1) Analogue transportation systems can easily accomodate for HD quality signal. Good quality component cables (or 3 times a BNC terminated coax cable) should be able to transport 1080p also. Don't misunderstand me here: digital offers benefits over analogue in terms of fault correction and is less prone to interference but it is absolutely untrue that an analogue signal is inferior to a digital one (for example VGA)

 

2) Why do CCTV camera's that output an analogue signal limit their video res. to about 576 x 720 then? Is it bandwidth? No. Is it because of the fact that CCTV images are/were primarily displayed on SD televisions? Possibly, but we do have HD TV's now.

 

I'll bounce back the question then: why not use higher res. camera's that output an analogue signal? IP is relatively new to the CCTV scene so a good argument is that the best of the best may still be analogue cams.

I believe to have read IP camera's are not brilliant at night and the analogue ones still beat them hands down in that department.

 

So, it would be nice to have a analogue camera out put 720P for instance. I'll have a capture card digitise this then. It is not inconceivable it will even do a better job than the A/D processor in an IP camera.

 

I'm looking forward to your thoughts on this one

Edited July 17, 2009 by Guest

[Soundy 1]

hi guys,

 

I know I'm new so my apologies if this is a moot or dumb question. I start out with the strangest questions first

 

Coax is essentialy a composite signal (includes both luminance and chrominance information and in case of regular TV also audio). I won't delve to deeply but sending this over 1 wire is asking for quality problems. Are there camera's which use Y/C (S-video, commenly called S-VHS) or YPbPr (component) or even RGB (also a component signal)?

 

It just doesn't make sense an expensive camera uses such an inferior video signal transport system. I suppose coax has plenty of bandwidth for B/W but when it comes to color it really is not the best choice. Any thoughts?

 

Component generally uses coax as well, it just uses three of them for one signal. Y/C cables are generally either twin-ax or have two coax pairs internally.

 

What you're really asking is, why composite video? Simple answer: cost and simplicity. Same reason 95% of home A/V components have until recently only had composite video.

 

For surveillance especially, there's not a huge benefit to Y/C or RGB, certainly not enough to offset the additional cost. As well, there's no suitable capture equipment (that I'm aware of) to record it. Y/C input is SOMEWHAT common on single-channel consumer capture devices, but even now, RGB input is rare until you get into HD equipment, and even for SD capture, it's pretty pricey... extend that to 4, 8, 16 or 32 channels and the price becomes extremely prohibitive - IP at that point is far easier and cheaper.

 

Factor in as well, the cost of the actual cable - Cat5e is the same price or cheaper these days than coax, so why run three wires when you only need one?

 

I could go on about other issues that just pop to mind (imagine a component-in DVR with 48 BNCs for 16 component inputs?! Cameras with three BNCs for output??) but again, the main reason is cost-benefit. Given the relative (to TV/movie production cameras) low quality of most CCTV cameras, they wouldn't really gain anything from the added cable anyway.

[scorpion 0]

It is because no one has pulled 5 million dollars out of their pocket, and developed it.

 

You could easily shop around the different camera manufactures, and get them to agree to buy so many units, and to support a standard that you will issue.

 

Once you have enough preorders it should be easy to get a bank to loan you the money based on your preorders.

 

I think you are about to become very rich!

[Jeroen1000 0]

I can relate that 3 coax's for one signal may be pushing it for large installations. Good point.

 

But that is still no reason for this low resolution thing. In case I'm mistaking a single coax has more than enough bandwidth for a 1080p signal.

For me this feels like: want megapixel resolution? Fork out some money for an IP camera.

 

@scorpion: this will not cost a hughe amount of money. A 100 dollar webcam is even capable of this

 

@ Soundy, since you made a good point that 3 cables per cam is too much, why not provide higher resolution over that single cable then? Surely there is no real technical restriction here?

Many home A/V equimpment has had component and S-video for ages. Think of DVD-players and S-VHS vcr's.

[Soundy 1]

Hi scorpion thanks for you reply. I'll provide more insight to my initial question now:

 

The reason for not purchasing a camera that digitises the signal is twofold:

 

1) Analogue transportation systems can easily accomodate for HD quality signal. Good quality component cables (or 3 times a BNC terminated coax cable) should be able to transport 1080p also. Don't misunderstand me here: digital offers benefits over analogue in terms of fault correction and is less prone to interference but it is absolutely untrue that an analogue signal is inferior to a digital one (for example VGA)

 

1080p translates to 1920x1080 resolution... that's barely 2MP in terms of IP cameras. 3 and 5MP IP cameras are common now, and that limit will only go up... analog HD has already hit a ceiling there. Unless you come up with a new HD standard, that's something of a dead end.

 

2) Why do CCTV camera's that output an analogue signal limit their video res. to about 576 x 720 then? Is it bandwidth? No. Is it because of the fact that CCTV images are/were primarily displayed on SD televisions? Possibly, but we do have HD TV's now.

 

It's very simple: they use standard NTSC or PAL video technology. The camera AND capture technology is readily available and cheap. And more to the point, the standard has been around for 50 years, whereas analog HD standards have only been settled on relatively recently, and even at the consumer level, the recording systems are still relatively rare and expensive.

 

I'll bounce back the question then: why not use higher res. camera's that output an analogue signal? IP is relatively new to the CCTV scene so a good argument is that the best of the best may still be analogue cams.

 

Again, cost-benefit. Single-input analog-HD record devices are rare and expensive at the consumer level... they'd be even more so for multi-input devices. You'd also have to convince manufacturers to incorporate that technology into their cameras, something that's not likely to show a cost-benefit for them. And you'd have to convince installers to run three times the cable, or use UTP with RGB baluns, which are also prohibitively expensive and fairly limited in quality and resolution supported.

 

I believe to have read IP camera's are not brilliant at night and the analogue ones still beat them hands down in that department.

 

Only partially true. The problem is not IP cameras specifically, but the fact that *megapixel* technology is still new and going through growing pains. Whether it's IP has no bearing on the camera's light-sensing capabilities; as an example, Panasonic makes an IP version of their very excellent WV-CW484 Super-Dynamic III dome camera. It's essentially the same high-quality camera, with the video digitizer and network interface built-in. The camera is designed for NTSC/PAL output, however, so even over IP, the output resolution is only 640x480 (rumor is Panasonic will be releasing megapixel versions of their new SD5 cameras).

 

In the end, remember that the GOAL of surveillance is not the same as for TV and movies. The GOAL is not super-quality video for people to sit back and immerse themselves in, it's to record activity on a number of fronts, essentially for record-keeping, and usually to store that for a long period of time. Remember that HDTV also operates at 30, 60, or even 120fps, whereas most surveillance is recording at 5fps or less. Once again, cost-benefit: in most instances, full-motion video is not as important as reduced storage requirements.

[Soundy 1]

@scorpion: this will not cost a hughe amount of money. A 100 dollar webcam is even capable of this

 

Yes... and it's digitizing the video internally and transmitting it over USB.

 

@ Soundy, since you made a good point that 3 cables per cam is too much, why not provide higher resolution over that single cable then? Surely there is no real technical restriction here?

 

No, but again, it will require an entirely new video standard. You'd then need to get both the camera and the DVR manufacturers onboard to develop that standard and design hardware to support it. They'll only do that if, as Scorpion suggests, you provide them lots and lots of development money, or if they see a substantial enough market for it.

 

At this point, you're moving into a market that's already addressed by megapixel IP cameras. Given the rate at which that market is growing, with prices dropping accordingly (economy of scale!), and the fact that it would take years to bring such a new standard to market, I don't think you'll find anyone interested in building it.

 

Oh, BTW, there is a method already to get that high-res video over a single coax: http://www.veracityusa.com/products/products.php

 

Many home A/V equimpment has had component and S-video for ages. Think of DVD-players and S-VHS vcr's.

 

Those also use connectors that are unsuitable for CCTV installations - S-video connectors in particular are prone to falling out on their own.

[survtech 0]

There is an entirely new (for CCTV) standard developed for digital over coax (and later twisted-pair and fiber). It's called HDcctv. Check out the HDcctv Alliance's website at http://www.highdefcctv.org/.

[thewireguys 3]

The Axis Q1755 has component video output at 1080i and 720p. Besides a spot monitor I don't really have a use for it.

 

http://www.axis.com/files/datasheet/ds_q1755_35818_en_0905_lo.pdf

[Squiffy 0]

The MAC variants were along the lines suggested by the OP:

http://en.wikipedia.org/wiki/D-MAC

 

The audio was the only part digitized, the video remained analogue with the multiplexed system.

 

The systems have been phased out (but maybe still in use in some parts of the world) and replaced by digital systems.

[Tailbone215 0]

I can relate that 3 coax's for one signal may be pushing it for large installations. Good point.

 

 

It's easier to just use UTP/Baluns for your analog installations.

[Jeroen1000 0]

 

1080p translates to 1920x1080 resolution... that's barely 2MP in terms of IP cameras. 3 and 5MP IP cameras are common now, and that limit will only go up... analog HD has already hit a ceiling there. Unless you come up with a new HD standard, that's something of a dead end.

.

It is the HDMI specification they upgrade. There is now support for for 4K x 2K resolution. I Don't have any say in that I'm afraid

 

2) Why do CCTV camera's that output an analogue signal limit their video res. to about 576 x 720 then? Is it bandwidth? No. Is it because of the fact that CCTV images are/were primarily displayed on SD televisions? Possibly, but we do have HD TV's now.

It's very simple: they use standard NTSC or PAL video technology. The camera AND capture technology is readily available and cheap. And more to the point, the standard has been around for 50 years, whereas analog HD standards have only been settled on relatively recently, and even at the consumer level, the recording systems are still relatively rare and expensive.

And that is what I regret really. I'm at home in the IT world where developments go really fast. I thought I had to be missing something here. As for as resolution goes advancements appear to stand still.

My point is: if an IP camera can hold the hardware required to encode the picture information, using let's say,H.264, a capture card will be able to do that also. They just don't make them . Also note ATI and NVIDIA's GPU's can encode (one at the time) video stream to H.264. The chip technology to encode a video file to MPEG4 IS availble now. So it all boils down to a caputure card which can do this with multiple streams (doesn't geovision have one?). But when there are no non-ip cams that output a higher res. this is a moot point.

 

 

Again, cost-benefit. Single-input analog-HD record devices are rare and expensive at the consumer level... they'd be even more so for multi-input devices. You'd also have to convince manufacturers to incorporate that technology into their cameras, something that's not likely to show a cost-benefit for them. And you'd have to convince installers to run three times the cable, or use UTP with RGB baluns, which are also prohibitively expensive and fairly limited in quality and resolution supported.

As I already said, I see the disadvantage of running 3 coax cable. I don't however see the problem of camera's outputting a higher resolution and sending that through 1 coax (apart from cost that is). I kind of ranted on about the rest above:)

 

Only partially true. The problem is not IP cameras specifically, but the fact that *megapixel* technology is still new and going through growing pains. Whether it's IP has no bearing on the camera's light-sensing capabilities; as an example, Panasonic makes an IP version of their very excellent WV-CW484 Super-Dynamic III dome camera. It's essentially the same high-quality camera, with the video digitizer and network interface built-in. The camera is designed for NTSC/PAL output, however, so even over IP, the output resolution is only 640x480 (rumor is Panasonic will be releasing megapixel versions of their new SD5 cameras).

What you are saying is that few manufacturers combine the good from the analogue cams with the convenience from IP cams? Some like Panny do. Would indeed make a great cam if they can beef up the res.

In the end, remember that the GOAL of surveillance is not the same as for TV and movies. The GOAL is not super-quality video for people to sit back and immerse themselves in, it's to record activity on a number of fronts, essentially for record-keeping, and usually to store that for a long period of time. Remember that HDTV also operates at 30, 60, or even 120fps, whereas most surveillance is recording at 5fps or less. Once again, cost-benefit: in most instances, full-motion video is not as important as reduced storage requirements.

 

60 fps is where is maxes out when it comes to unique frames. The rest is 'intelligent' frame creation by the TV circuitry or repeat frame.

 

Thanks for all the insights. I did have a motive for asking all this. As I value your pro input, in your opinion, is the analogue res. enough to recognise the face of the burglar/vandal if using a quality analogue cam, good IR-lighting and the right lens?

 

Or should I go the IP cam route trying to find one which offers good night time vision? In any case, I will be using a computer to caputure/store the video. How much more will this cost over the analogue solution:

 

Analogue: Capture card + software + camera + IR lighting. Cable is not really expensive.

 

Digital: Software (probably included with the camera) + camera + CAT5 cable or wireless.

[scorpion 0]

Hello everyone!

 

I am ready to throw out all of my customers SD analog cameras!

 

You know the expression "and don't let the door hit you on the way out"!

 

The true answers, and questions about HDCCTV will revolve around cost factors. If you cannot replace the customer's cabling, and they cannot migrate to IP megapixal cameras, then HDCCTV will be a large revenue stream for your company!

 

This will be a boon to many mom n pop video surveillance companies that have never learned more then just networking a DVR to a router.

 

Will the IP megapixal market "fight" the HDCCTV market to win market dominance?

 

I look forward to pulling some cameras off of some building here in the near future!

[Soundy 1]

 

1080p translates to 1920x1080 resolution... that's barely 2MP in terms of IP cameras. 3 and 5MP IP cameras are common now, and that limit will only go up... analog HD has already hit a ceiling there. Unless you come up with a new HD standard, that's something of a dead end.

.

It is the HDMI specification they upgrade. There is now support for for 4K x 2K resolution. I Don't have any say in that I'm afraid

 

Does the new spec also extend the effective length of HDMI cables beyond 60 ft.?

 

Once again, CCTV has different goals than HDTV. HDMI is impractical for the majority of CCTV applications.

 

My point is: if an IP camera can hold the hardware required to encode the picture information, using let's say,H.264, a capture card will be able to do that also. They just don't make them .

 

Pretty sure they do, actually... you still need three times the encoding power to process component video, if that's how you're getting the analog signal to your DVR. Those requirements are not likely to be very attractive to developers.

 

 

Again, cost-benefit. Single-input analog-HD record devices are rare and expensive at the consumer level... they'd be even more so for multi-input devices. You'd also have to convince manufacturers to incorporate that technology into their cameras, something that's not likely to show a cost-benefit for them. And you'd have to convince installers to run three times the cable, or use UTP with RGB baluns, which are also prohibitively expensive and fairly limited in quality and resolution supported.

As I already said, I see the disadvantage of running 3 coax cable. I don't however see the problem of camera's outputting a higher resolution and sending that through 1 coax (apart from cost that is). I kind of ranted on about the rest above:)

 

Already addressed that: there is currently no analog HD standard that supports this, and developing one at this point would be meaningless with the other options alread available. You'd never be able to recoup the costs, even IF you could get manufacturers *and users* onboard.

 

Only partially true. The problem is not IP cameras specifically, but the fact that *megapixel* technology is still new and going through growing pains. Whether it's IP has no bearing on the camera's light-sensing capabilities; as an example, Panasonic makes an IP version of their very excellent WV-CW484 Super-Dynamic III dome camera. It's essentially the same high-quality camera, with the video digitizer and network interface built-in. The camera is designed for NTSC/PAL output, however, so even over IP, the output resolution is only 640x480 (rumor is Panasonic will be releasing megapixel versions of their new SD5 cameras).

What you are saying is that few manufacturers combine the good from the analogue cams with the convenience from IP cams? Some like Panny do. Would indeed make a great cam if they can beef up the res.

 

I expect it's been mainly an issue of priorities. You already have analog cams ranging from cheap, low-TVL, poor-low-lux, to high-TVL, super-dynamic, starlight-illumination, infrared and thermal cameras, in a correspondingly wide range of prices. The only real barrier was the resolution limitations of NTSC/PAL video. So the next step was to select a transmission method for higher-resolution cameras.

 

HDTV standards had barely been ratified and accepted by the industry, and adapting existing systems and designs to that would have been expensive. Meantime, 100Mbit ethernet was dirt-cheap and GBe prices were dropping fast. Hubs had already become obsolete and switches were cheap. IP was a natural choice if for no other reason than the timing of it.

 

You still have your camera sensor, and your video digitizer... but instead of using a low-resolution analog transmission medium to tie them together over a distance, you just build the two together, and use a digital distance-transmission method instead.

 

In the end, remember that the GOAL of surveillance is not the same as for TV and movies. The GOAL is not super-quality video for people to sit back and immerse themselves in, it's to record activity on a number of fronts, essentially for record-keeping, and usually to store that for a long period of time. Remember that HDTV also operates at 30, 60, or even 120fps, whereas most surveillance is recording at 5fps or less. Once again, cost-benefit: in most instances, full-motion video is not as important as reduced storage requirements.

 

60 fps is where is maxes out when it comes to unique frames. The rest is 'intelligent' frame creation by the TV circuitry or repeat frame.

 

Thanks for all the insights. I did have a motive for asking all this. As I value your pro input, in your opinion, is the analogue res. enough to recognise the face of the burglar/vandal if using a quality analogue cam, good IR-lighting and the right lens?

 

The only answer to that question is, "it depends". With a tight shot on the area of concern (say, a 36"-wide door, or other access bottleneck), you can easily get recognizable faces out of an analog camera. Megapixel simply gives you the option to cover a wider area with the same detail, or pull higher detail out of the same area.

 

Look at it mathematically: if your analog capture card samples at 640x480, and your 1.3MP camera outputs 1280x1024, you have double the horizontal and vertical resolution; for that given coverage area, the detail you get out of one 1.3MP camera would require *four* NTSC cameras to achieve the same level of detail.

 

Or should I go the IP cam route trying to find one which offers good night time vision? In any case, I will be using a computer to caputure/store the video. How much more will this cost over the analogue solution:

 

Analogue: Capture card + software + camera + IR lighting. Cable is not really expensive.

 

Digital: Software (probably included with the camera) + camera + CAT5 cable or wireless.

 

Again, "it depends". If you're just talking about one or two cameras, going with a system that uses an 8- or 16-input card is probably overkill and you're paying for a lot of additional capacity you don't need. If lighting isn't a problem, an MP cam will provide you far better detail; if lighting is an issue, well, you can get MP cams with good low-lux performance, but they'll be a lot pricier.

 

You have to remember to separate "IP" from "megapixel" to some degree here, because any standard analog camera can be run over IP with the use of a video-encoder box. If an analog camera is sufficient (or required by other factors), and you have networking already in place, this can save you substantially on installation costs over having to pull new coax and paying extra for unneeded capacity.

 

What you want to do with the video can also be a factor, since if you don't need to record the video locally, an IP-based camera will generally have the ability for you to view it remotely via network, as well as to email or ftp images and video clips to you or a remote server - thats even more savings without having a dedicated local recorder and the ability to simply plug the camera into any handy network port. Try THAT with HDMI

[kensplace 0]

composite video over coax can go quite a fair distance, certainly longer lengths than say s-video is capable of.

 

Lots of installations of CCTV cams have the cams located a long way from the DVR, s-video is not suitable for transmission over long distances, whereas composite over coax is.

[rory 0]

why use a gas when you can use deisel?

why use email when you can use a phone?

 

some big brand box cameras had S-VHS outputs .. for spot monitors though, because the cost of using S-VHS cable costs alot more. I use to use it on the CCTV monitors also, and time lapse VCRs, not that long ago actually, but who uses Tubes and VCRs these days?

 

Oh wow man .. this is whack .. check this old diagram out .. actually it still works to get better quality playback from DVRs, we all have seen the crappy quality on LCDs:

[ak357 0]

1) Analogue transportation systems can easily accomodate for HD quality signal. Good quality component cables (or 3 times a BNC terminated coax cable) should be able to transport 1080p also. Don't misunderstand me here: digital offers benefits over analogue in terms of fault correction and is less prone to interference but it is absolutely untrue that an analogue signal is inferior to a digital one (for example VGA)

 

2) Why do CCTV camera's that output an analogue signal limit their video res. to about 576 x 720 then? Is it bandwidth?

 

I'll bounce back the question then: why not use higher res. camera's that output an analogue signal? IP is relatively new to the CCTV scene so a good argument is that the best of the best may still be analogue cams.

 

So, it would be nice to have a analogue camera out put 720P for instance. I'll have a capture card digitise this then. It is not inconceivable it will even do a better job than the A/D processor in an IP camera.

[/quote/

-------------------------------------------------------------------

 

You may like this twist

Security cam with SDI output (by the way standard BNC)

meaning Reg Coax cable

transmitting video up to 200 meters

Data rate up up 3 Gig/sec

capture card (BNC input) and software do compression

by the way true 1080i at 30 Frames and 720P

[Jeroen1000 0]

Thanks for the thorough answers again. It will be a tough decision to make. The forum still holds a ton of info I need to plow through! Thanks again for setting me on my way guys.

[normicgander 0]

2/2008

 

While progressive scan digital (output ) cameras are needed and will be the future, I’m not a big fan of Ethernet (IP) based cameras. Perhaps the IP video surveillance industry was too caught up in the cute concept of “convergenceâ€