It seems to be an article of faith that when it comes to pixels, more is better. We seem to have lost sight of the fact that all pixels are not created equal. Pixel colors are encoded as RGB or YCrCb, but with HDR, ATSC 3.0 enhances the fourth dimension of luminance. With today’s NEXTGEN TV broadcasts of 1080p+HDR you experience 85% of the maximum improvement you will ever get over the ATSC 1.0 world of 1080i+SDR. This blog explores this 85% claim.
Improvement in Video Quality
The Numbers
When you look at the chart above, the first thing that pops out is that 4K video has 8 million pixels compared to 1080p video that has 2 million pixels. What gets missed is that ATSC 1.0 video can only show 17 million colors per pixel compared to 1 billion colors for ATSC 3.0. Further, ATSC 1.0 video can show a luminance range that is less than 10% of the ATSC 3.0 range.
ATSC 1.0 HD video can be 1080i or 720p. This means that each frame has either 1 million or 1.4 million pixels. Each pixel is represented by 24 bits of color for a total of 17 million colors. ATSC 3.0 video today is 1080p where each frame has 2 million pixels. HDR broadcasts use 10-bits per color for a total of one billion colors compared to 17 million with ATSC 1.0. HDR also conveys a much wider range of luminance for each pixel that is used to control the light intensity and color of the LEDs behind the pixels. All this means that HDR video is much richer and vibrant. It renders moving images on the TV screen that mirror much more closely what our eyes see in nature. With HDR, the colors pop.
The Three Video Options
During the current ATSC 1.0 to ATSC 3.0 transition there are three major options to display video:
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ATSC 1.0 video with SDR and 1080i or 720p
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ATSC 3.0 video with HDR+1080p upscaled to 4K
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ATSC 3.0 video with HDR+native 4K
Today’s NEXTGEN TV broadcasts use HDR+1080p. With most receivers you get HDR+1080p upscaled to 4K. Is it worth waiting for HDR+native 4K? We just released support for “Advanced HDR by Technicolor”. In the process we learnt a lot more about HDR (see FAQ #59 at https://zapperbox.com/pages/faqs). What we learnt surprised us, so we spoke with a few video experts. Their consensus was that 80% to 90% of video quality improvement over ATSC 1.0 comes from “HDR+1080p upscaled to 4K”. Most viewers cannot tell the difference between that and “HDR+native 4K”. One anecdote we heard “stand within 6 feet of two side-by-side TVs, now watch the dots on the newscaster’s tie, the ones in native 4K look better.” Seriously? Is that worth the wait?
The 1080p vs. 2K Confusion
This goes back to the advent of analog TV. Broadcasters measure resolution in vertical scan lines while CE manufacturers specify displays in number of horizontal pixels. Consequently, a 1080p broadcast is equivalent to a 2K display. 1080p sounds like 1K when in reality those signals have 2K horizontal pixels. The comparison is really HDR+2K vs. HDR+4K. However, with the advent of High Dynamic Range or HDR, the number of colors per pixel goes up from 17 million to one billion and the luminance range increases over ten times. While the human eye can tell the difference between a 2K and 4K display on a laptop screen at 18 inches, it can barely tell them apart at normal TV viewing distance. That’s when the one billion colors of HDR become 4X more impactful than 4K pixels.
And Then There’s the Sound
If HDR makes the colors pop, Dolby® Atmos closes the deal. ATSC 1.0 uses 2-dimensional Dolby 5.1 surround sound with five audio channels for front-left, center, front-right, rear-left, and read-right plus one channel for bass. This is two-dimensional sound on the X-Y axis. ATSC 3.0 uses Dolby 7.1.4 (Atmos-pheric 3-dimensional sound). On the X-Y axis it adds the mid-left and mid-right channels. It also adds up to four Z axis height channels for front-left-height, front-right-height, rear-left-height, and rear-right-height.
The Bottom Line
HDR + “1080p upscaled to 4K” + Dolby Atmos closes the deal for moving from 1990s ATSC 1.0 technology to today’s ATSC 3.0 NEXTGEN TV. When native 4K broadcasts happen today’s receivers will be ready for the final miniscule improvement, but chances are that you will not even notice the difference.
