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A couple of weeks ago in news of someone coming out with 8K resolution televisions, I left a comment to the effect that I have a 4K TV, but there's no 4K content, so an 8K TV was a bit silly. Someone said they thought Netflix had a couple of 4K offerings.
I recently ran across news that I'll have 4K content in the nebulous future. The FCC [US Federal Communications Commission] is taking its first steps toward over the air 4K broadcasts. but it appears that it may be a while before I see it.
There's more about it here at CNet. But all three articles raise questions that aren't answered, primarily, what about bandwidth? It seems to me that without extremely tight lossy compression, it would take four times the bandwidth of 1080p. Will quality be much better than 1080p after they compress the signal?
How will they get around that? Will I lose some side channels? What do you folks have to say?
(Score: 2, Informative) by Anonymous Coward on Monday February 06 2017, @02:21PM
But all three articles raise questions that aren't answered, primarily, what about bandwidth? It seems to me that without extremely tight lossy compression, it would take four times the bandwidth of 1080p. Will quality be much better than 1080p after they compress the signal?
Real-world video signals don't need 4x bandwidth for 4x pixels; as you increase the number of pixels, only a few of the new pixels (basically those in high-detail areas) actually add information, while many pixels are effectively redundant (areas of even or smoothly-changing colors), and compress to almost nothing. The result is that you typically need only 2x to 3x bandwidth for 4x the pixels (when going from e.g. 540p to 1080p; if anything, this ratio should get better going from 1080p to 2160p, at the same subjective quality.
Originally, ATSC used MPEG-2 compression, for a maximum of 1080i60 (or 1080p30) in a 19 Mb/s stream. The full 19 Mb/s would be enough for a rather high quality encoding, but is generally not used -- by reducing quality a little, space is made for subchannels and such.
The recent revision from 2008 allows H.264 (aka MPEG4 AVC) for up to 1080p60 -- again, the full 19 Mb/s would not be used. Not sure how widely this is deployed
Between the nonlinear bitrate increase and H.265's better compression (only 50-70% bitrate for same subjective quality as H.264), it looks like 2160p60 is just about in reach. If a bit more bandwidth is still needed, it can probably be managed by either squeezing quality a bit more, or by killing off subchannels. For comparison, Netflix uses 15.6Mbps for 4k* -- however, I believe that's for 24/30 fps streams, though a 60fps stream carrying 24/30fps content (e.g. most movies and prime-time TV) would be essentially the same. True 60fps content, on the other hand, would need increased bandwidth or decreased quality.
*not sure if that figure is for H.264 or H.265, but it doesn't matter, as the figure's from a couple years back when H.265 was new and they weren't seeing a difference between H.264 and H.265; H.265 encoders have gotten better since then.
(Score: 0) by Anonymous Coward on Monday February 06 2017, @02:49PM
It's yet another proprietary, patent-encumbered technology; surely, for the sake of the entire computing world, it would be far superior to coalesce around an unencumbered technology such as Google's AOMedia Video 1 [wikipedia.org]
(Score: 0) by Anonymous Coward on Monday February 06 2017, @03:27PM