1080p50 is very good indeed why isn’t broadcast tv 1080p50? I mean why is it 1080i25?
The 1080p50 being provided OTT by Amazon Prime is almost certainly a deinterlace from 1080i25 (which has the same motion as p50)
Broadcast outlets aimed at TVs use 1080i because TV has been interlaced since 1936 (the original 405line standard was 377i25) and either display it native interlaced (CRTs and early ALiS Plasmas) or deinterlace from i25 to p50.
Computers, tablets and phones don't always have decent deinterlacing built in (and it takes processing power to do it) so for OTT platforms a progressive format is always preferred. Until recently (iPlayer was the first UK platform to switch from p25 to p50 a couple of years ago) all OTT was p25. This is fine for drama and documentary (which is shot progressive at 25Hz), but terrible for sport and entertainment that is shot at 50Hz.
1080p50 is do-able as a native origination format - but is relatively rare - as there are no major linear broadcast outlets that take it. If an event is being shot primarily for streaming it can be shot 1080p50 (most modern cameras and infrastructure supports the 3G-SDI required for 1080p50 and 1080p59.94)
In Germany and the Netherlands their DVB-T2 platforms are using 1080p50 HEVC/h.265 encoded - but I believe a lot of this is 1080i25 deinterlaced to 1080p50. (HEVC isn't optimised for interlaced content in the same way that h.264 is)
To be honest - the quality difference between 1080i25 deinterlaced well and native 1080p50 is quite small - HDR and UHD make more of an impact (HDR particularly)
The key thing to always remember is that 1080i25 isn't 25 pictures per second. It's 50 - the same number of pictures per second as 1080p50. This is why 1080i25 and 1080p50 have the same fluid motion. The difference is that 1080p50 native has full vertical resolution irrespective of content (as it sends 50 1080 line pictures each second), whereas 1080i25 has reduced vertical motion on moving content, with only static content having the higher vertical resolution (as it sends 50 540 line pictures each second, but the two pairs of 540 line pictures that make up a frame are offset vertically with respect to each other). Motion blur on moving content is entirely normal - so people don't perceive it as a major quality issue.
LOTS of people think 1080i25 has the same motion as 1080p25 because it has the same frame rate - ignoring what interlace is and how it works
Last edited by noggin on 24 June 2019 4:24pm
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