Adrian Pennington goes behind the scenes of War Horse as the National Theatre production becomes the first event to be aired live to cinemas in 4K.
The 4K stage production of the National Theatre's War Horse claimed a number of firsts when it aired on 27 February. Not only was it the first live-to-cinema 4K transmission, it was the first commercial run for the format in which cinema-goers at Chelsea's Curzon paid to see the 180-minute event. It also necessitated the world’s first high framerate 4K Digital Cinema Package (DCP).
National Theatre Live (NT Live) broadcast War Horse from the New London Theatre to over 1000 cinemas worldwide – most of them live but with many also showing delayed 'live' screenings. All but one of those was an HD broadcast, but the significance of the sole 4K TX points the way to the future.
Technical producer for NT Live, Creative Broadcast Solutions (CBS), together with NEP Visions, NT Live’s long-term OB partner, partnered with satellite provider Links Broadcast and Sony to deliver the event, which is NT Live's 36th stretching back to 2009.
“We regularly cover NT Live productions in HD but the National Theatre thought that War Horse was such an important show that it should ideally be captured with large format cameras,” explains David O'Carroll, technical projects manager, NEP Visions. “What was equally important was maintaining the HD workflow since that feed was going to the majority of cinemas. We built a 4K layer into the flypack installed onsite complemented by an audio truck and a second truck for graphics, subtitles and autocue.”
Six F55 CineAlta cameras equipped with Fujinon Cabrio lenses fed 4K video into BPU4000 fibre adapters which generated 4K and HD signals simultaneously. The BPUs are an essential piece of kit, allowing the F55s to be used as a system camera with rack and control. The feeds were presented at a Sony MVS-8000X switcher as four HD 3G signal (quad 4K) to create the live mix.
NEP Visions were tasked with creating three paths: a 4K mix with graphics; an HD version of same and another HD path with subtitles. The mix feed was recorded on a Sony MasterDeck, for archive and the creation of a 4K DCP master that will be distributed to cinemas. NEP Visions also recorded 4K ISOs onto two additional Sony MasterDecks for later use.
The F55s were positioned in the middle of the stalls (one on a jib, one remote controlled on a hot head) arrayed in an arc and shot mindful of a cinema audience watching on 15m screens.
As usual with NT Live performances, the stage director, broadcast director (in this case, Tim Van Someren) and production teams (including NT Live producer Emma Keith) got a chance to review footage shot during a rehearsal to see if any tweaks to coverage were required. Digital Cinema lab Soho Digital Cinema (SDC) created a 4K DCP for them to view it projected on a cinema screen.
“There were no significant game-changing differences versus HD,” noted Chris Bretnall, technical producer for NT Live at Creative Broadcast Solutions.
Links Broadcast provided the satellite uplink and downlink facilities to enable the delivery of the 4K signal (and simultaneous HD signal) from the New London Theatre into the Curzon Cinema in Chelsea. Using four synchronous Adtec EN-100 encoders the incoming signal was combined into a single transport stream in MPEG4 via an Adtec DTA3050 multiplexor for onward transmission via a 1.5m antenna on Links’s 4K uplink vehicle.
“We made an initial test using a truck on location to ensure we could transmit a 4K signal and then we did a glass-to-glass test at Visions taking the camera signal into a 4K projector,” explains Links business development manager Andy Tweedley.
The signal was then uplinked on to SES Astra’s 3B satellite using 36Mhz of capacity in order to achieve the maximum possible video data rate within the modulated 4K transport stream.
“4K live to a projector had never been done before so we had to do a lot of testing to get the suitable video bitrate,” says Bretnall. “Typical HD relays that go to cinemas use approx 18-19Mbps within a 36Mhz carrier. Now we are getting over 100Mbps within the same bandwidth.”
The incoming signal was downlinked at the Curzon via a 1.8M Links Broadcast receive antenna which was fed into Adtec RD70 receiver decoders and delivered to the projector.
Audiences will be able to view the performance recorded in Ultra HD with a live feed encoded standard Digital Cinema Initiatives (DCI) compliant DCP. In charge of this were SDC who were presented with a huge challenge. Currently 4K HFR is only a proposal in the recommendations of the DCI, the governing body that sets digital cinema standards.
The Hobbit 3D films, for example, were shown at 24p for each 'eye', whereas War Horse was able to shoot and screened as a single eye 50p. To get there SDC had to devise a new workflow in order to work with Sony’s latest SRMaster format. This included ingesting 4K 50p material from SR-R1000 decks and encoding using a new beta version of DVS Clipster programmed especially for this project.
SDC, Sony and NT Live successfully tested a 4K DCP from Sony's SRMaster, which is currently confirmed to work with Sony’s SRX-R320 4K projectors.
“4K HFR is an incredible spectacle to behold,” commends Soho Digital Cinema managing director David Margolis. “If 8.5 million pixels weren’t enough resolution, seeing them dance at 50fps results in the smoothest, most immersive digital cinema content we’ve ever seen.”
In the UK, approximately 500 screens showed War Horse live with many also showing a delayed version. In the US, around 300 screens took the live feed and another 100 showed delayed. Canada featured 100 showings; Europe approx 80, and in the rest of the world, including Australia, Russia, Mexico, and Japan, there were 80 delayed shows.
The technical set up was very similar to that of a live sports event. In fact, Andy Hotten, Sony's technical project manager, was in Turkey the week before War Horse overseeing a 4K production for Turkish satellite broadcaster Digiturk of a Galatasaray and Besiktas match in which four F55s and two upconverted HDcams were fed through a MVS-8000X and linked back to a hotel for a VIP screening.
“After War Horse we will have established a proven workflow for 24p 4K distribution with an option for cinemas to take it to 50p 4K,” says Bretnall. “We know that many cinemas are capable of showing 4K and we know a small number capable of showing it live with few additional high hurdles than for last the 35 NT Live productions.”