Everything is happy in TV land.īut let's say there's a sportsball guy running across your screen from right to left. With 1080i, on the other hand, it's getting half a snapshot every 60th of a second (1,920x540 every 60th).
It's that 1080i is worse with fast motion than 720p.Īt 60 frames per second (720p), the camera is getting a full snapshot of what it sees every 60th of a second. As we said earlier, this largely wasn't based on some limitation of the technology or being cheap.
ABC and Fox very consciously made the choice to go with 720p over 1080i. Let's take the example of the sports from earlier. If only it were that easy (if that is even easy)
In a TV review, this is the main thing we're checking when we test deinterlacing prowess. Many early 1080p HDTVs did this, but pretty much no modern one does. If it's done wrong, the TV instead takes each field, and just doubles the information. If it's done right, the TV repeats each full frame to create 60 "fps" from the original 30. This is when the TV combines the two fields into frames. When your TV is sent a 1080i signal, however, a different process occurs: deinterlacing. Check out my article, appropriately called " What is upconversion?" for more info on that process. For most sources, this is from a process known as upconversion. Yes, what about it? Your 1080p TV accepts many different resolutions, and converts them all to 1,920x1,080 pixels. Your TV combines these together to form a complete frame of video. Of the 1,080 lines of pixels, the first field will have all the odd lines, the second field will have all the even lines. Each field is 1,920x540 pixels, every 60th of a second. What this means is that even though there are 30 frames every second, it is actually 60 fields. The 1080 image is actually "interlaced." That's where the "i" comes from.
Back in the olden days of the '90s, however, we weren't so lucky. How, you might ask, does this 30fps work on TVs designed for 60? With modern video processing, the frame rate doesn't matter much. The math is actually pretty simple: 1080 at 30fps is the same amount of data as 720 at 60 (or at least, close enough for what we're talking about). This is what CBS, NBC, and just about every other broadcaster uses. The 1080i designation is 1,920x1,080 pixels, running at 30 frames per second. This is because when it comes down to it, fast motion looks better at 60fps (more on this later). Both ABC and Fox have big sports divisions, which played a big role in their decision to go with 720p. Sure, we all knew they were coming, but it was years before they started shipping (now, almost all TVs are 1080p). The first, in the late '90s when all this was happening, there were no 1080p TVs. I've seen some reader comments in response to other articles I've written ridiculing ABC/Fox for this "lower" resolution, but that's unfair in two big ways. This is the format used by ABC, Fox, and their various sister channels (like ESPN). OK, 720p is 1,280x720 pixels, running at 60 frames per second (fps). Let's start with 720p, as it's the easier to understand. Let the argument commence.īecause our TV world is based around 60Hz, and because there's a limit to how much resolution could be transmitted over the air (because of bandwidth and MPEG compression), the two main HDTV resolutions are 1080i and 720p. True, 1080i and 1080p aren't the same thing, but they are the same resolution. And, you can't even get a full 1080p/60 source other than a PC, camcorder, or some still cameras that shoot video. From one perspective, 1080i is actually greater than Blu-ray. There still seems to be some confusion about the difference between 1080i and 1080p.