So, if you're a video quality stickler like me, streaming your TV shows and movies from the internet is the only way to go.
Plus, it's unlikely that cable companies will be able to push a 4K video signal through the existing cable TV infrastructure, so internet streaming or 4K Blu-Ray is the only way to watch 4K content in the foreseeable future.
So why do cable companies use the clearly inferior 1080i?
It's all about bandwidth. Cable TV providers simply don't have enough bandwidth to deliver a 1080p signal where every frame contains the whole picture at 60 frames per second. So, it sends 1080i signal, where only half of the picture is contained in every frame.
Meanwhile, the 1080p video feed from your streaming device delivers every row of pixels in every frame.
Every row of pixels – all 1,080 of them – is being loaded up onto your TV screen in every frame. In turn, that means there's no chance for the frames to be out of sync with each other, like they are with 1080i, and the video looks sharper.
But why does 1080i look fuzzy?
1080i video looks fuzzy because each frame of odd and even pixel rows don't quite line up with each other, as the video has progressed from one frame to the next. It's especially noticeable where there's a lot of movement in a scene.
Essentially, each frame containing the odd and even rows of pixels are displaying two different parts of a video's timeline. Each frame is only milliseconds or less apart, but it's enough to give off that ghosting effect where you see a trail of an object on the screen. Hence, you get that fuzzy look on cable TV video
That's because 1080i displays alternating frames, with each frame only containing half of the picture.
Here's what's happening:
- During each second of 1080i video, you're seeing 60 frames.
- However, each frame does not contain the whole picture. Bear with me here.
- With 1920 x 1080 resolution on a TV, there are 1,080 rows of pixels going across the screen (those rows are 1,920 pixels long, hence the 1,920 x 1,080 number used to describe the resolution).
- Each frame alternates between flashing an odd row of pixels, which covers 540 – or half – of the 1,080 rows of pixels on a 1080 TV. Once the frame with the odd row of pixels has been flashed, the next frame flashes the remaining 540 even rows of pixels.
- The odd and even frames flash so rapidly – 30 times per second each – that it looks like a complete picture.
Both display the same 1920 x 1080 resolution, but cable TV's 1080i video can look slightly fuzzier than a video stream's 1080p video, especially during scenes where there's a lot of movement.
Above, the video on the left is using interlaced scanning, and the video on the right is using progressive scanning.
The video in this GIF has been slowed down to show you the effects of interlacing. It's less noticeable when the video is playing at normal speed, but it's still there and makes the overall picture look less sharp than progressive scanning.
