Live from Cardiff: Sky Sports brings UHD to pay-per-view and trials high-speed cameras
Last Saturday’s world unification title fight between Joseph Parker and Anthony Joshua at Cardiff’s Principality Stadium was not just the first pay-per-view boxing match to be broadcast in Ultra High Definition (UHD).
It was also an event notable for a few other Sky Sports firsts and technology trials, particularly its use of high-speed UHD cameras.
“We trialled the Sony 4800 at our boxing at the O2 arena in London [for Dillian Whyte versus Lucas Browne], and it looked fantastic running at 8x speed [400 frames per second] in UHD,” says Jennie Blackmore, production manager, Sky Sports.
This success meant it brought two to Cardiff – one positioned on a corner, at head height, the other at a low angle ring side, shooting up through the ropes.
“We were thinking, before the O2, that we would try it at 4x, but actually using it 8x got some beautiful hi-mo shots,” she adds. “And we managed to get a large amount of replays out using both cameras.”
The issue always is having the time to replay that clip, adds Robin Broomfield, Sky Sports’ technical manager.
“But they make the clips pretty short, and at 400fps it is a fantastic shot,” he says. “It is a large-sensor camera, with a PL-mount, film lens on it [Canon CN7x17], so the quality is really good. We tested the 4800 a while back, and it was quite noisy.”
As a result, they hadn’t used it since, but as the production team really wanted the UHD slow motion, they opted to try it again, and as it was so successful at the O2, they decided to use two for Joshua-Parker.
“It took them a little while to find the sweet spot and get the focus there, but within 20 to 25 minutes things were looking better.”
The O2 trial also helped Sky to decide on the right lenses for Cardiff. Depth of field was especially critical – slo-mo cameras already need more light, so the lenses have to be wide open, and having a larger sensor exacerbated that, so the cameramen had to adapt.
“It took them a little while to find the sweet spot and get the focus there, but within 20 to 25 minutes things were looking better,” he says.
Certainly, the results did look spectacular, but the shallow depth of field did mean parts of each boxer were out of focus.
Testing the workflow
The production at the O2 was all done in UHD and delivered back to Sky as such, but was only broadcast in HD.
However, it meant they got to test the complete workflow, and were then able to bring the same truck and equipment to Cardiff
“We didn’t want our first UHD experience to be on a Box Office [pay-per-view] event where we hadn’t trialled it before,” says Blackmore, so it was fortunate to have such a similar production only the weekend before, which enabled them to identify any issues – the main one being the UHD RF camera (of which, more later).
The 4800s were run on SMPTE fibre into a Sony server (one per camera), separate to the EVS replay network.
“The user interface is very similar to EVS so the guys got across it very quickly,” says Broomfield. Sony handled the installation for each of the servers, integrating them into the VT area.
The main production cameras, the Sony 4300s, can run at 2x speed in UHD, but were only used at standard speed – except for one run at 3x speed 1080/50p.
One of the principal attractions of the Principality Stadium is that it has a roof to protect from the Easter downpours.
The roof took six hours to close, to allow time to fit the rigging points for the “mother grid”, which is what the truss for the lights, PA and video screens above the ring was hung off.
“Normally, for a stadium like this, they put in a canopy, like they did at Wembley for Joshua vs Klitschko, but that means that a lot of the seats around the top tier have to get blocked out because of sight lines,” explains Blackmore.
The canopy legs would also block views but having a higher grid like this means more seats, culminating in an audience of about 80,000 people.
“It’s expensive to put in the roof rigging, but they make up for it in the extra seats they sell.”
“There is a lot of processing going on, it gets quite hot, and it failed a couple of times.”
Both Sky Sports and its US counterpart Showtime had identical presentation platforms on one end of the arena floor, both with two small presentation platforms off to the side: one for Sky Sports News, the other for the French station SFR.
Rather than Spidercam, which Sky used at Wembley, it used the point-to-point Eaglecam system, provided by Alan Wells. This was suspended on a single wire from one corner of the stadium to the other.
“It gets a nice overhead shot of the ring walks,” says Blackmore.
Because of the trusses, the Eaglecam couldn’t go above the ring, but could give a good shot running past one corner. It was fitted with a 1080/50p camera, chosen because it was RF, which hasn’t so far proved sufficiently reliable in UHD to be used on such a vital camera.
Ring walks and pyrotechnics
In fact, the Eaglecam did have a few RF issues, “but produced some fantastic overhead shots, especially of the ring walks and pyrotechnics,” she adds.
The other core cameras were its usual boxing set up, including several wireless 1080/50p cameras, and two Jimmy Jibs, one ring side, going over the top for in-fight coverage, and one on its presentation platform, as the main presentation camera, which also does sweeping crowd shots.
Sky also used Batcam Hold, a small 1080/50p wireless camera, to give a close-up, selfie-style shot of Joshua walking out for the ring walk without the operator being in his face.
That camera is used a lot for English Football League matches, given to the teams when they win for celebratory shots.
Sky Boxing had used it once before, but not with the radio link, when they gave it to Joshua to use in his dressing room, recording in camera.
“This is the first time we’re using it as a live camera,” reveals Blackmore, and it “went really well” with “solid pictures all night on the RF link. The operator managed to get in the thick of it with the ring walks, which gave the viewers the experience of actually being part of Joshua’s entourage.”
Wireless UHD “is nearly there, but not quite”
There were also minicams in each dressing room for arrival shots, among other things.
“The feed of Joshua’s camera also goes back via a Mobile Viewpoint unit for our social media team to stream and use as they want,” says Blackmore.
Sky used social media to extend the reach of its coverage, putting the first hour of coverage and the early undercard bouts out on Facebook Live before the Box Office output kicked in.
There were also VR cameras positioned near the top of all four ring posts – but on their own poles to avoid vibration.
The recordings required post-production so weren’t available live, but are now viewable via an app.
Because the 360-degree cameras are small and black, they aren’t very noticeable, and the promoters Matchroom and the British Boxing Board of Control (BBBC) were very accommodating, the Sky team say.
Problems persist with RF UHD
Wireless UHD “is nearly there, but not quite,” says Broomfield, which is why Sky has been running its wireless cameras at 1080/50p and upconverting over the last two seasons of UHD football.
It uses a Kahuna mixer in most of its trucks, which has a Format Fusion standards conversion layer on both input and output, which handles the upconversion.
“To have that in a vision mixer takes away a lot of the processing we’d have to do externally otherwise,” continues Broomfield. “It makes life really easy. Feeding in 1080p50, the upconversion is relatively straightforward and it looks very good.”
Although it works sufficiently well, Broomfield admits that you can notice the difference on larger TV sets, especially at 65-inches and above.
An H.265 RF link was tested at the event. supplied by Broadcast RF. Broomfield says the reliability is not there yet.
“There is a lot of processing going on, it gets quite hot, and it failed a couple of times.”
There were modifications made between the O2 and Cardiff, but it was still used purely as an extra camera.
The system made use of a Vislink UHD transmitter and receiver fitted to a Sony PXW-Z450 B4-mount UHD camcorder.
Matthew Bowers, an RF engineer for Broadcast RF, could see “vertical tearing between the top two and bottom two [quadrants], where they’re not quite meshing together. The transmitter and receiver both went back for upgrades after last weekend, and we’ve had them on the bench for the last couple of days and haven’t seen anything in the workshop.”
The main problems had been where there were large differences in contrast, such as a referee with a white shirt under the lights against a dark background, although reproducing the fault on the test bench proved difficult, which is why it has to be tested in a real production.
The RF system was used with a delay of 100 to 120 milliseconds (20ms of which was running through a SAM unit as there wasn’t genlock on the receiver, but a genlock update is due soon).
A longer delay could give higher quality results, but Bowers hasn’t seen that yet as everyone wants the shortest delay possible for live sports.
He believes that UHD RF has been developing quite rapidly recently, “and I don’t think it will be long until it is very dependable. There are a few little kinks to iron out.” Once he’s confident that the tearing issue has been fixed “I’d be more than happy to take it anywhere.”
Despite the extra processing required with running UHD, the system lasts about the same length of time on a battery as its HD systems, which is between 60 and 90 minutes.
The UHD workflow
The truck used was Telegenic’s T25 which handles UHD as four 50p 3G-SDI quadrants.
Its EVS replay system was run at 1080/50p, however, because “you need a lot of servers to run UHD,” says Broomfield.
It would be possible in UHD, but moving content around for analysis, highlight compilation or playout takes more time which is why he thinks they will stick with 1080/50p until the next generation of EVS, which should have much faster connectivity.
“Sky’s specifications are at least 75% [of a production] must be native UHD. We hit that very easily because all of the main cameras are UHD. When you look at the replay side of it, that’s only a small percentage of the total programme. Into that we’ve actually put in this time, two native UHD high-motion replays [from Sony] separate to the EVS network, which has increased the percentage, because those cameras get the majority of the good replays as they are in a good position to get those shots.”
When you look at the replay side of it, that’s only a small percentage of the total programme.
Using the 4800s did mean changing the workflow slightly, something they usually try to avoid, but the previous week’s trial at the O2 helped greatly in getting everyone used to the new servers.
The systems also have to cope with lots of different formats, whether ENG material or HD upconverted from Sky’s MAM. This stores HD at 50i, which is upconverted on outgest to 1080/50p, and transferred from XAVC to DNx (as used to run replays in the truck).
Similarly, archive from the truck is recorded at 1080/50p and then transcoded to 50i for the MAM. Sky also archives the UHD separately in XAVC.
Crucially, content that has been round-tripped from HD 50i, upconverted and later downconverted for HD broadcast, loses very little quality. “At the end of the day, the HD service is actually the most important service, because that’s where the majority of our viewers are,” he says.
Sky normally uses a different Telegenic truck for boxing but chose the T25 because of the requirement for UHD.
“The advantage of having all of our trucks the same is that we can drop in whatever suits us technically and production won’t know the difference,” says Telegenic unit manager Martyn Edwards. “UHD for us is normal. We do an awful lot of it, it’s just applying it to a different sport.”
The truck also handles the operation of the big screens in the stadium, which requires down conversion, plus a lot of monitoring returns for the international commentators.
“It’s just making sure we have enough glue [mainly from SAM, plus Lawo V_pro8] to down-convert and provide everything we need to,” says Edwards. “The UHD radio camera is great, but it is another load of glue to get it working with the truck including down-conversion for monitoring and use with the EVS systems.”
Large screen UHD monitoring is also an issue – as the OB team have to use domestic sets which don’t deliver reliable colour performance, and aren’t robust enough to survive a life on the road.
“They’re not that expensive. We just have to keep changing them,” says Edwards.
The HDR conundrum
Although shooting UHD, Sky is not yet using high dynamic range (HDR) for live production, as Broomfield explains.
“HDR is something we are looking at, but dynamic range and wide colour gamut is something for the future. It’s not far away. We’ve done some testing. It does look better, especially for sports like football where you have bright sunlight and half the pitch in shadow.”
While it can handle the high dynamic range and standard dynamic range, the key problem he sees is up- and down-mapping the colour spaces to/from Rec.709 and BT.2020.
Although Sky is doing a lot of production using HDR, shooting Log gamma formats and grading in post, live isn’t there yet.
“The maths in mapping a colour from one colour space to another is very critical, and it is that side of the technology that isn’t ready yet,” he says, explaining that that it is giving the wrong hue, and needs a lot more testing before it is ready for transmission.
Its failures are most noticeable in mapping the very bright colours often found in a footballer’s jersey or boots, he adds.
“We want to make sure we’re in a position where we’re getting everything right.”
This is particularly important for branded colours, such as Coca-Cola red. “Branding definitely needs to be right,” he states.
HDR is one of the areas he will be looking at during NAB, as well as at developments in high frame-rate production, which will also be important for sports.
Anthony Joshua vs. Joseph Parker took place on 31 March 2018 at the Principality Stadium in Cardiff and was broadcast live on Sky Sports Box Office.
*Robin Broomfield will be one of the panellists on the Global Perspectives in Sports Production: Europe session at SVG’s 2018 Chairman’s Forum on Saturday 7 April in Las Vegas.