no more hslv format ?

[Christopher Woods]

On 3 May 2018 21:38:23 RS <richard22j at zoho.com> wrote:

> On 03/05/18 12:18, Steve Dodd wrote:
>
>> Is it possible it depends on the source material? From the BBC quote
>> earlier it sounds like their "source" material is still mostly HD
>> interlaced, but perhaps some of their sources are all also
>> progressive, and those ones get doubled identical frames (which might
>> be a logical result of feeding 25p material into something that's
>> designed to interpolate interlaced fields into frames)?
> The satellite broadcasts I have seen from the BBC and other broadcasters
> are 1920x1080i25 for HD and 720x576i25 or 704x576i25 for SD.  Everything
> that is broadcast is in an interlaced format at some stage, however it
> is generated.  Some programmes are only produced for the iPlayer, so
> they may be generated in a different way.


A handful of HD is still 1440x1080i25 :( the non-square pixel format is a 
great cheat for bandwidth saving. The chroma compression on current 
generation terrestrial broadcasting also makes everything look bad. Once 
you watch uncompressed HD-SDI you never want anything else :) Some SD is 
way below what we would accept as SD resolution as well, all in the name of 
cost saving.


Steve is right on the doubled technique, this is the filmic look you see on 
documentaries and dramas. That source material will be likely be captured 
as progressive frames, then upconverted to 50 fields per second, 
'progressive segmented frame' format (PsF) in the edit.

The same image is stored across every two fields that constitute one frame, 
meaning you're being shown one effective whole full resolution image, 25 
times a second.

With standard interlaced footage, you're being shown overlapping effective 
'images' at half-resolution, 50 times a second. Persistence of vision 
(well, nowadays, flat panel processing circuitry) bob deinterlaces the 
fields to produce 50 images per second.


However, TVs sometimes do this artificially by taking true progressive 
sources and interpolating the footage to a higher refresh rate (100/200 
Hz). This inherently looks dire and should be disabled.

On some TVs with poorly written image DSP (or badly chosen settings) you'll 
see the picture suddenly go 'filmic' as the deinterlace method changes to 
blend, which literally blends together pairs of fields to produce 25 frames.

Some explainers of fields, frames and progressive segmented format interlaced:

https://en.m.wikipedia.org/wiki/Progressive_segmented_frame

https://wolfcrow.com/blog/understanding-terminology-progressive-segmented-frames-psf/
https://wolfcrow.com/blog/understanding-terminology-progressive-frames-interlaced-frames-and-the-field-rate/