Future Tech Trends | Hybrid Log Gamma
More HLG content is expected to be created this year
HLG is a concept birthed by the BBC and Japan ' s NHK
“ If you ’ re watching Wimbledon on normal television , and suddenly you ’ re panning across the crowd and people are wearing white shirts , you ’ ll very rapidly see those white shirts lose all detail , they ’ ll become very flat .
“ Already cameras have to deal with more light than they ’ re set-up for . So cameras have always had a knee , and that knee is to say ; as the light levels go up , I can ’ t carry any more light and I have to start flattening . They also tell the camera that it ’ s impossible for any more output for that light .
“ HLG is a very clever extrapolation of camera knee technology , from a normal gamma curve . It ’ s essentially the splicing together of two curves , it gives us a better transfer function . It ’ s designed so there is defined headroom in the camera to cover the spectrum of highlights . Rather than each cameraman doing their own thing and having different shaped knees , we have a defined range where we can carry the highlights .”
Those are the basics of HLG , but what about the technical specifications ?
Well , Phil says that they ’ re set out in BT . 2100 ; an ITU standard . HLG is also going to be part of HDMI , although it ’ s a single bit change meaning it ’ s down to manufacturers to decide whether they want to support it or not . This is an update to HDMI 2.0 , however , and not HDMI 2.1 – meaning users won ’ t need new cables or receivers .
The BBC concedes that it isn ’ t planning to release a lot of HLG content anytime soon . In fact , just one programme is encoded in the format at this moment in time . Despite
that , it ’ s getting closer to being ready for prime time , as signalled by the BBC ’ s open testing of the format .
In December 2016 , the BBC began the first public trial of HLG , although it didn ’ t exactly go to plan . The idea was to allow viewers to enjoy Planet Earth II in UHD through the BBC iPlayer App on select smart TVs , with the hope that HLG would activate on the TVs that support the format . Unfortunately , the BBC overestimated the number of TVs in the marketplace that had HLG technology activated – and those that did , resulted in streaming errors when trying to play the content .
That ’ s not exactly a great start . Although it has taught the BBC some important lessons . “ One of the things that the Planet Earth trial revealed to us , was that the streaming system that we felt , or were led to believe , had been widely implemented by manufacturers wasn ’ t actually as widespread .” That streaming system was DVB- DASH , which , thankfully for the BBC , is becoming more prominent in devices shipping this year .
“ It ’ s the chicken and the egg problem really . We have to know there ’ s enough receivers in the market to make it worthwhile . So , having learnt what we learnt about some of the receivers in the market , we are trying to work with manufacturers this year to get much better interoperability between the streaming formats .”
It ’ s not just the BBC ’ s investment in UHD and HLG that is dictated by the receivers in the wild either . The BBC admits that it ’ s hard to entice content creators to spend the extra cash required for working with UHD footage , especially when there aren ’ t that many people in the world able to experience it . That ’ s part of the reason Planet Earth II is the only programme utilising the format .
“ There are extra costs . Shooting UHD for the Natural History Unit really doesn ’ t cost them very much more , but for a drama programme , some have shot in UHD , but they ’ ve post-produced in HD . There are extra costs that the programme will need to spend and if there isn ’ t a market for that piece of content in UHD , then that ’ s money the producer won ’ t want to spend at this moment in time .
“ The NHU is the natural home , because they ’ ve actually shot UHD , higher resolutions than HD , for some considerable time as part of their production process . We ’ re hoping that there will be other bits of content available over this year and hopefully live content year .
10th-11th May 2017 , Sandown Park , Surrey . Sponsored by March 2017 | 25