1080i VS 1080p The Difference

1080i vs. 1080p: What's the Difference?

Progressive (1080p) video is considered better than interlaced (1080i), but it's not always clear why; here's what's actually happening on your TV screen.

Today's HDTVs can display beautiful, 1,920 X 1,080-pixel video, but the actual quality of what you're viewing depends on the source material. A lot of the time, you're not seeing exactly 1080p. In fact, most TVs today have two modes with similar names: 1080i and 1080p. Both have the same screen resolution, so what's the difference between the two? Here are five things you need to know:

1080i video is "interlaced." 1080i video plays back at 60 frames per second, but that's a bit deceptive, because it's actually broadcast at 30 frames per second. The TV then displays those frames twice, the first pass is 1,920 X 540 for the even scan line field, and the second pass is 1,920 X 540 for the odd scan line field. The process by which this occurs is called interlacing. It contributes to a sense of motion and reduces perceived flicker.

1080p video is called "progressive scan." In this format, 1,920-by-1,080-pixel high-definition movies are progressively drawn line after line, so they're not interlaced. On paper, that may not seem like a huge deal. But in the real world, what you end up seeing looks sharper and more defined than 1080i, particularly during scenes with a lot of fast motion.

Sometimes 1080p is termed "Full HD" or "True HD," to distinguish it from 1080i or 720p video. Blu-ray discs contain 1080p video at 24 Frames Per Second, and then, using a method known as 3:2 pulldown, display it at 30 frames per second on screen.

Data compression can confuse the issue. Sometimes cable companies will deliver a 1080i picture, but then compress the data significantly in order to use up less bandwidth. The result can mean smeared details or pixelated color gradations in certain scenes. It's still technically HD, and still looks better than standard-definition cable, but it's not as good as it could be.

This also happens with 1080p streaming Internet video, but in that case, it's usually dependent on the speed of your data connection. In fact, Blu-ray is currently the only practical format for watching lots of pure 1080p content. Even the latest Apple TV, which supports 1080p streaming, does so in a compressed format that loses a bit of quality (although it still looks quite good).

Both formats look similar on smaller TVs. As a general rule, you need a larger TV to notice the difference between 1080i and 1080p. Depending on your eyesight, you can probably pick up the difference on a 32-inch LCD if you're particular about it. But most consumers don't really see a marked difference until at least a 42-inch screen, if not larger. In fact, many people are perfectly happy with 720p HDTV sets even at higher sizes; we recently named one, the 51" Samsung PN51E490B4F, best Choice for budget large-screen HDTVs.

1080p isn't even the best anymore. Technology never stands still, of course. Five years from now, you'll probably just want Ultra High Definition (aka 4K) video instead. (For a closer look at 4K video, check out What is Ultra HD?) But for now, if you're a videophile who appreciates a sharper picture, 1080p is definitely the way to go—both in HDTV capability and in the source material you're viewing.

To 4K or not 4K video or Ultra HD

To 4K or not to 4K video or Ultra HD

Our industry’s seemingly insatiable appetite for more and more resolution has now produced a wave of interest in 4K cameras that promise exceptional clarity and sharpness, akin to the big screen, Ultra HD television sets found in consumer electronics stores and an increasing number of North American homes.

The jury is still out on whether there is an immediate need for the resolution that can overcome the downsides of increased storage and bandwidth required for running 4K cameras in a surveillance operation. Like so many things, if the cost of the camera, cost of the supporting system infrastructure and components were of no concern, this new format would likely be a more viable and attractive option for many security applications.

Here are four things to consider before making the leap to investing in and deploying 4K video:

1. What will I get with 4K that is not possible at lower resolution?

There’s no doubt that 4K technology is light years ahead of analog quality, but the reality is that the increased clarity and sharpness provided by that level of resolution is often over and beyond what is required and able to be managed by a typical security operation. For many reasons, full HD/1080P is the most commonly used resolution for new systems. The majority of security systems in use for live monitoring situation do not really benefit from such a resolution, as the human eye is well served with the details of a 1080P picture. Higher resolutions pay out when more details are required in forensic investigations.

2. Double the resolution, double the processing requirements

Users typically want to see more than one camera on one monitor, and only  occasionally switch to full screen modes. With 4K, the clarity of that multi camera view would be no clearer than what would be viewed from a lower resolution camera. In addition, delivering streams from multiple 4K cameras presents some technical challenges. The client PC and graphics card must handle a significant flow of data. The best approach is to have the live view limited to only enough resolution for the video size and screen resolution of the display.

Today a typical approach to balance PC power requirements and quality uses lower resolution streams for live view, while recording in the highest resolutions. 4K resolution taxes the workload on the network because recording the highest resolution means the full stream content moves from the camera to the NVR.

3. Limitations on form factors, lenses

The availability of affordable high resolution optics is just not there yet, and a dome style camera with a typical curved dome bubble cannot transmit the 4K resolution. In addition, a true 8MP resolution lens with appropriate coverage for the 4K sensor is quite large, which would render a 4K version of the compact dome camera (the market’s favorite form factor) essentially not possible.  The dome camera would get physically bigger which, for many customers, is a negative.

4.  Bandwidth and storage requirements

From a cost perspective, quadrupling the resolution from full HD to 4K won’t quite double the camera price. However, on the recording side it will most definitely demand more than double the storage requirements when operating under the same conditions.

Bandwidth consumption is related to processor power available on the camera. For example, the average full HD cameras deliver about 6Mbps at 30 ips. On the bright side, some manufacturers are offering full HD models with advanced compression capabilities that can reduce bandwidth consumption to about 3Mbps, with the next iteration to handle 4K video at full HD bandwidth consumption levels. Additionally new compression standards such as H.265 HVEC (High Efficiency Video Encoding) will make higher resolution bandwidth more practical for surveillance.

So where does this leave you, 4K today or not just yet? For some customers a bigger number is frequently perceived as a better solution but surveillance installations should focus on the reason the system investment is being made in the first place; protection of personnel and protection of assets. It is far from a one size fits all decision and resolution is an important tool in the system solution.

Next benchmark for video surveillance cameras is going to be the Ultra HD standard, with a resolution of 3840 x 2160 – around 8MP. Given the challenges networks may face carrying Ultra HD video streams it’s hard to say just when we will see the technology reach a tipping point.

THERE are a couple of signs worth paying attention to with Ultra HD (commonly called 4K in consumer and CCTV industries). The first is that UHD consumer monitors, which are now dropping in price at a time many homeowners’ first 1080p HD monitors may be starting to look a little tired. Something else to bear in mind is the consensus forming in digital photography that 8MP is the sweet spot that allows the best balance of low light performance and high resolution.

As most readers know, the more pixels you cram onto an imager, the smaller those pixels must be. And the smaller the pixels, the less light they can absorb. Double the number of pixels on a 1/3-inch HD sensor and you halve the light reaching the sensor. The result is that more pixels does not a perfect camera make – not unless sensor sizes increase. If it’s all about display images today, then 3MP cameras with a 1080p resolution are ideal.

But if you need digital zoom or you use a UHD monitor, then Ultra HD cameras should be a consideration. If you zoom in 2x digital with an Ultra HD image then you are viewing at 2MP, which is pretty good considering how quickly it takes an HD camera to burrow down under 4CIF when digital zoom is applied. 

Something else to bear in mind when considering digital image quality is that pixels on a digital camera’s sensor capture light in red, blue or green – not all colours at once. A layout will be a pair of green, a red and a blue in a grid pattern and onboard software then nuts out the colour value for pixels. This means there’s signal attenuating averaging going on in the background - one colour per 4 pixels.

A camera’s digital engine is also working hard to stave off false colours and moire – spacial aliasing that causes false patterns in a scene. Camera engines will blur an image slightly then sharpen it in order to lose such artifacts. Clearly, the more pixels, the more work the camera processor has to get through and this can be noticeable as latency or blurring if there’s sudden movement – like cars moving at right angles across a scene.

Lenses are another issue. An Ultra HD camera is going to need a quality lens and there’s no doubt that plenty of 1080p cameras are being sold with lenses that are not perfect. Sure, things look good in the centre of the image but out towards the edges details get muddy, especially on the sorts of deep zooms that might motivate a buyer to choose Ultra HD in the first place.

Sensor noise is also something that has to be considered at multiple levels. In low light, cameras increase exposure, elevating noise levels. Furthermore, pixel measurements are never perfect and the flaws in these signals show up on a monitor as noise. It’s unhelpful during the day and blinding at night. Digital noise reduction is the answer but DNR processing doesn’t just lose noise, it sloughs fine detail off a scene. When you look at a camera being tested in low light you can often see the areas where DNR has scrubbed and smudged a scene free of detail. It’s not a good look.

Engineers can build high resolution imagers with fewer noise problems but they need to be big – 1-inch or 1/1.5 inch sensors are ideal. A 1/1.5-inch sensor has 4x the area of the 1/3-inch sensors that typically run inside 1080p CCTV cameras. No wonder GBO’s S1080 camera (BGWT sells them in Australia) with its monster 1-inch sensor has such a great image in low light.

If the sensors are large enough, the lenses are good enough, the network is capable enough and the storage sufficient, then Ultra HD cameras will give end users a lot more detail than 3MP 1080p cameras can. But this capability has to be balanced against many things. Image quality is about more than megapixel count. 

“If a sensor is of the similar size as the equivalent HD sensor and it has 4x the pixels - low light performance will be 4x lower. And streaming bandwidth will be close to 4x larger unless better compression is used”

Keep in mind,

4K =     8.3 megapixels, aspect ratio 16:9 Horizontal resolution

1080p= 2.1 megapixel,  aspect ratio 16:9 Vertical resolution

720p=   1.3 megapixel,  aspect ratio 16:9 Vertical resolution

D1=      0.4 megapixel,  aspect ratio   4:3 Vertical resolution