How good is HD supposed to be?

[Tony Quinn]

On 30-Apr-16 9:15 PM, Dave Liquorice wrote:

> But does a frame have the same number of lines as a field? It doesn't 
> in the analog world. 625 line frame, comprising two 312.5 line fields. 
> Frame rate 25 per second, field rate 50 per second but half the 
> vertical resolution. If a digital field only has half the vertical 
> resolution, which I think it must have or you can't interlace them, 
> then to create true 50 *frames* per second each field needs to be 
> upscaled and the missing lines interpolated from the existing ones. If 
> you just construct a frame from the two fields you have to repeat that 
> frame or playback at double speed... I missing something but don't 
> know what. 

1080p50 (720p50) is exactly what it says, 50 full 1920x1080 (1280x720) 
progressively scanned frames per second (naturally this generates twice 
as much information as 25p (although 720p50 is the same raw data rate as 
1080p25)).

Going back to an earlier comment on the thread regarding eastenders 
being available at 720p50, given that EE is originated at at 1080 
resolution, is the implication that it is being shot at 1080p50 and down 
converted to 720p50 or that interpolation is being carries out to 
generate a 720p50 stream?

FWIW, in interlaced origination (for example 625i50) temporal resolution 
is increased at the cost of spatial resolution (twice as many images 
with half the vertical resolution). Also bear in mind that (in the 625 
analogue world) only 575 lines actually contain picture information