Originally Posted by holl_ands
Au Contraire.....Netflix recommends at least 15 Mbps Internet Service for their "4K" Streams and ATSC 3.0 OTA Test in Cleveland is using a very generous 15.7 Mbps for "4K" Transmission plus some other Programs...out of a Total of 26 Mbps. As H.265 "4K" Encoder/Decoders improve, the required Data Rate for the same PQ will slowly come down over time. Bear in mind that when tested a few years ago, H.265/HVEC was about TWICE as efficient as H.264/MPEG4...which in turn is about TWICE as efficient as MPEG2.....so we're looking at about 4:1 Efficiency improvement....and probably TWO "4K" Programs in a single 6 MHz Bandwidth Channel as the Encoder/Decoders and HVEC compatible StatMuxes improve:
For bitrate comparisons :
The BBC UHD tests last summer using DVB-T2 modulation were carrying 30+Mbs 2160/59.94p and 2160/50p HEVC encoded video in a 40.25Mbs 8MHz T2 mux. The Astra 2 UHD demo I can tune on my UHD set via the built in DVB-S2 tuner is quite optimised but running with a video bitrate of around 23Mbs for 2160/50p 10bit.
This compares to around 8-15Mbs being used for 1080i and 720p streams using H264 in Europe (often dropping lower or undemanding material if statmuxing used) UHD is carrying 8 times the picture content of HD (ignoring 8-10 bit issues) :
UHD 2160/50p = 414,720,000 pixels per second (3840x2160x50)
HD 1080/50i = 51,840,000 pixels per second (1/8th UHD rate) (1920x1080x25 if you think in frames or 1920x540x50 if you think in fields)
HD 720/50p = 46,080,000 pixels per second (1/9th UHD rate) (1280x720x50)
(UHD 2160/24p = 199,065,600 pixels per second - this is what Netflix carries)
So you have to carry 8 or 9 times the picture information of an HD signal to deliver an equivalent UHD signal. H264 should offer around 2:1 efficiency over MPEG2, and HEVC should offer around 2:1 efficiency over H264, though I'm not sure we're there yet.
So you should be able to carry an HEVC signal of the same format in 1/4 the bandwidth of an equivalent MPEG2 signal. So you're looking at around twice the bandwith for UHD in HEVC over HD in MPEG2? (8 times the content but carried 4 times more efficiently) ? There is probably an argument that you can reduce the differential because you may not need twice the bitrate to go from 50i to 50p?