How good is HD supposed to be?

[Christopher Woods]

Replied inadvertently to some of this in my other response, but everyone 
may find this interesting if they've not read before:

http://www.bbc.co.uk/rd/blog/2015-07-the-development-of-new-video-factory-profiles-for-bbc-iplayer

There's an 8 mbit 1080i created which I strongly suspect is what's 
delivered to Sky for their on-demand iPlayer offerings, certainly from 
watching some stuff on my Sky+ box. The DOG was smaller and "1080 crisp" 
(as was the picture content) on my panel which it never is using the web 
iPlayer.

>From the R&D blog:

"The [encoding] profiles were designed to be encoded with a 3.84 second 
chunk size. This enables video and audio access units to be aligned for 
HTTP Live Streaming (HLS), where audio and video frames are multiplexed 
together within a single MPEG-2 transport stream, thereby helping some 
decoders have a clean switch between profiles. During subjective evaluation 
done within R&D, we identified that large screen devices such as TVs 
benefited more from higher frame rates than small screen devices such as 
tablets, where spatial resolution is of greater importance. In addition 
higher framerate 50Hz television streams still exhibit motion artefacts on 
most mobile, tablet and desktop devices due to their 60Hz screen refresh 
rate. So separate profile sets were developed for the two classes of devices."


On 30 April 2016 22:36:51 Tony Quinn <tony at tqvideo.co.uk> wrote:

> 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
>
>
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