We don’t need to be running a recording studio to care about speaker placement. Broadcast facilities are full of audio monitoring rooms for a range of uses. The principles discussed in this talk by award-winning studio designer Carl Tatz can be put in to practice wherever you want to sit in a room and listen to decent, flat audio.
Joining Producer Mike Rodiguez who moderates this webinar for the Audio Engineering Society (AES), Carl focuses this discussion on getting the right sound in audio control rooms. This is done through the ‘Null Positioning Ensemble’ (NPE) which considers the mixing console, listener and the speakers ‘as one’ that can be moved around the room. The ensemble puts the two speakers at about 1.71m apart behind the console firing across the console. Their audio intersects 45cm in front of the console where the listener can sit forming an equilateral triangle. By sitting between the console and where the speakers cross, Carl says you hear the source rather than the speakers thus giving the best audio reproduction.
This effect works if the tweeters are at the same higher as the listener’s ears, says Carl, so should be adjusted to suit the listener. High frequencies are more directional than lower frequencies so for accurate listening, it’s important the speakers aren’t pointing too far off-axis. Exactly where to place your ensemble can seem daunting, but Carl has a calculator on his website which gives a great start allowing you to model your room as a rectangle and find out where the null points are going to be. The nulls are where sound cancels out due to reflections so moving your ensemble to avoid these nulls is the key to a great sound. Carl details how this is done and how, then, to optimise for the ‘real world’ room rather than the mathematical model.
Carl talks about the importance of sound treatment to remove reflections and stop the room from being too lively, with some specific suggestions. In general, the aim is to remove first reflections, have the back stony dead, the ceiling dead and bass traps in the corners. This should allow you to clap your hands without hearing reflection. But you can’t fix every problem with such treatment, Carl says, bringing up a frequency chart of a typical monitor setup which shows a 10dB dip around 125Hz. This is found in all monitoring setups and appears to develop from sound from the speakers bouncing off the floor under the console. He says that this needs to be filled in with subwoofers rather than being fixed with EQ or acoustic treatments.
How deep do you want to go to make sure viewers get the absolute best quality streamed video? It’s been common over the past few years not to just choose 7 bitrates for a streamed service and encode everything to those bitrates. Rather to at least vary the bitrate for each video. In this talk we examine why doing this is leaving bitrate savings on the table which, in turn, means bitrate savings for your viewers, faster time-to-play and an overall better experience.
Jan Ozer starts with a look at the evolution of bitrate optimisation. It started with Beamr and, everyone’s favourite, FFmpeg. Both of which re-encode every frame until they get the best quality. FFmpeg’s CRF mode will change the quantizer parameter for each frame to maintain the same quality throughout the whole file, though with a variable bitrate. Beamr would encode each frame repeatedly reducing the bitrate until it got the desired quality. These worked well but missed out on a big trick…
Over the years, it’s been clear that sometimes 720p at 1Mbps looks better than 1080p at 1Mbps. This isn’t always the case and depends on the source footage. Much rolling news will be different from premium sports content in terms of sharpness and temporal content. So, really, the resolution needs to be assessed alongside data rate. This idea was brought into Netflix’s idea of per-title encoding. By re-encoding a title hundreds of times with different resolutions and data rates, they were able to determine the ‘convex hull’ which is a graph showing the optimum balance between quality, bitrate and resolution. That was back in 2015. Moving beyond that, we’ve started to consider more factors.
The next evolution is fairly obvious really, and that’s to make these evaluations not for each video, but for each shot. Doing this, Jan explains, offers bitrate improvements of 28% for AVC and more for other codecs. This is more complex than per-title because the stream itself changes, for instance, GOP sizes, so whilst we know this is something Netflix is using, there are no available commercial implementations currently.
Pushing these ideas further, perhaps the streaming service should take in to account the device on which you are viewing. Some TV’s typically only ever take the top two rungs on the ladder, yet many mobile devices have low-resolutions screens and never get around to pulling the higher bitrates. So profiling a device based on either its model or historic activity can allow you to offer different ABR ladders to allow for a better experience.
All of this needs to be enabled by automatic, objective metrics so the metrics need to look out for the right aspects of the video. Jan explains that PSNR and MS-SSIM, though tried and trusted in the industry, only measure spatial information. Jan gives an overview of the alternatives. VMAF, he says, ads a detail loss metric, but it’s not until we start using PW-SSIM fro Bright cove where aspects such as device information is taken into account. SSIMPLUS does this and also considers wide colour gamut HDR and frame rates. Similarly ATEME’s ‘Quality Vector’ considers frame rate and HDR.
Dr. Abdul Rehman follows Jan with his introduction to SSIMWAVE’s technologies and focuses on their ability to understand what quality the viewer will see. This allows a provider to choose whether to deliver a quality of ’70’ or, say, ’80’. Each service is different and the demographics will expect different things. It’s important to meet viewer expectation to avoid churn, but it’s in everyone’s interest to keep the data rate as low as possible.
Abdul gives the example of banding which is something that is not easily picked up by many metrics and so can be introduced as the encode optimiser continues to reduce the bitrate oblivious to the obvious banding. He says that since SSIMPLUS is not referenced to a source, this can give an accurate viewer score no matter the source material. Remember that if you use PSNR, you are comparing against your source. If the source is poor, your PSNR score might end up close to the maximum. The trouble is, your viewers will still see the poor video you send them, not caring if this is due to encoding or a bad source.
A wide range of topics today covering live virtual production, lenses, the reasons to move to IP, Esports careers and more. This is a recording of the SMPTE Toronto sections’ February meeting with guest speakers from Arista, Arri, TFO and Ross Video.
The first talk of the evening was from Ryan Morris of Arista talking about the importance of the move to IP. Those with an IP infrastructure have noticed that it’s easier to continue using their system during lockdown when access to the equipment itself is limited. While there will always be a need to move a 100Gbe fibre at some point or other, a running 2110 system easily allows new connections without needing SDI cables plugging up. This is down to IP’s ability to carry multiple signals, in both directions, down a single cable. A 100 gigabit fibre can carry 65 1080i59.94 signals, for instance which is in stark constrast to SDI cabling. Similarly when using an IP router, you can route thousands of flows in a few U of space where as a 1152×1152 SDI router takes up a whole rack.
Ryan moves to an overview of the protocols that make broadcast on IP networks possible starting with unicast, multicast and broadcast. The latter, he likens to a baby screaming. Multicast is like you talking to a group of friends. Multicast is the protocol used for audio, video and other essences when being sent over IP whether as part of SMPTE ST 2110 or ST 2022-6. And whilst it works well, the protocol managing it, IGMP, isn’t really as smart as we need it to be. IGMP knows nothing about the bandwidth of the flow being sent and has no knowledge of capacity or loading of any link. As such, links can get saturated using this method and can even mean that routine maintenance overloads the backup path resulting in an outage. Ryan concludes by saying that SDN resolves this problem. Ryan explains IGMP as analogous to knowing which address you need to drive to and simply setting off in the right direction, reacting to any traffic jams and roadblocks you find. In contrast, he says SDN is like having GPS where everything is taken in to account from the beginning and you know the whole path before you set off. Both will get you there, SDN will be more efficient, predictable and accountable.
Next in the line-up is François Gauthier who takes u through the history of cinema-related technologies showing how, at each stage, stanards helped the increasingly global industry work together. SMPTE’s earliest, well known, standardisation efforts were to aid the efforts around World War 1 interchanging films between projectors/cameras. Similarly, ARRI started in 1917 and has benefited from and worked to create SMPTE standards in cameras, lighting, workflows, colour grading and now mixed reality. François eloquently takes us on this journey showing at each stage the motivation for standardisation and how ARRI has developed in step.
A different type of innovation is on show in the next talk. Given by Cliff Lavalée updates on the latest improvements to his immersive studio. It was formerly featured in a previous SMPTE Toronto section talk when he explained the benefits of having a gaming-based 3D engine in this green-screen studio with camera tracking. In fact, it was the first studio of its kind as it came on line in 2016. Since then, game engined have made great inroads into studio production.
Having a completely virtual studio with camera tracking and 3D objects available to be live-rendered in response to the scene, has a number of benefits, Cliff explains. He can track the talent and make objects appear in front or behind them as appropriate in response to their movements. Real-time rendering and the green blank canvas gives design freedom as well as the ability to see what scenes will look like during the shoot rather than after. It’s no surprise that there are also cost savings. In one of a number of videos he shows, we see a children’s programme which takes place in a small village. By using the green screen, the live-action puppets can quickly change sets from place to place integrating real props with virtual backgrounds which move with the camera.
The last talk is from Cameron Reed who’s a former esports director and now works for Ross Video. Cameron gives a brief overview of how esports is split up into developers who make the game, tournament organisers, teams, live production companies and distribution platforms. The Broadcast Knowledge has followed esports for a while. Check out the back catalogue for more detailed videos on the subject.
It’s no surprise that the developers own the game. What’s interesting is that a computer game is much more complex and directly malluable than traditional sports games. Whilst FIFA might control football/soccer world-wide, there is little it can do to change the game. Formula 1 is, perhaps, closest to the esports model where rules will come and go about engines, tyres, refueling strategies etc. With esports, aspects of the game can change week to week in response to fans. Cameron explains esports as ‘free’ adverstising for the developers. Although they won’t always make money, even if they make 90% of their money back directly from the tournament and events for that year, it means they’ve had a 90% discount on their advertising budget. All the while, they’ve managed to inject life in to their game and extend the amount of interest it’s garnered. Camerong gives a brief acknowledgement that for distribution “Twitch is king” but underlines that this platform doesn’t support UHD as of the date of the meeting which doesn’t sit well with the efforts of the gameing industry to increase resolution and detail in games.
Cameron’s presentation finishes with a look at career progressions in esports both following a non/semi-technichal path and a technical path. The market holds a lot of interesting opportunities.
The session ends with a Q&A for all the panelists.
“Moving to the cloud” is different for each broadcaster, some are using it for live production, some for their archives, some just for streaming. While confidence in the cloud is increasing and the products are maturing, many companies are choosing to put their ‘second MCR’ in the cloud or, say, tier-2 playout to test the waters, gain experience and wait for a fuller feature set. Sky Italia, has chosen to put all its disaster recovery transmission capability in the cloud.
Davide Gandino joins us from Mile High 2020 to show – and demo – their disaster recovery deployment which covers playout, processing, distribution and delivery to the end-user. Davide explains this was all driven by a major fire at their facility in Rome. At the time, they managed to move their services to Milan with minimal on-air impact, but with destroyed equipment, they were left to rebuild. It wasn’t long before that rebuild was planned for the cloud.
This is no insignificant project, with 117 channels of which only 39 are third-party pass-through going on to four platforms, the full deployment uses 800 cloud encoders. This amounts to 4Gbps being sent up to the cloud and 8Gbps returning. David highlights the design uses both Google and Amazon cloud infrastructure with 3 availability zones in use for both.
A vital part of this project design is that not all 800 encoders would be working 24×7. This misses the point of the cloud, but the only scalable alternative is fully automated deployment which is exactly what Sky chose to do. The key tenants of the project are:
Everything automated – Deployment and configuration are automatic
Software Defined – All Applications to be software defined
Distributed – Distributed solution to absorb the loss of one site
Synchronised – All BAU (business as usual) changes to automatically update the DR configuration. This is done with what Sky call the ‘Service Control Layer’.
Observed – Monitoring of the DR system will be as good or better than usual operation
To active the DR, Davide tells us that there is a first stage script which launches a Kubernetes cluster on which the management software sits and 13 Kubernetes clusters across Google and AWS which will run the infrastructure itself. The second script, uses Jenkins jobs to deploy and configure the infrastructure such as encoders and DRM modules etc. Davide finishes the talk showing us a video of the deployment of the infrastructure, explaining what is happening as we see the platform being built.Watch now! Speaker
Head of Streaming, Cloud & Computing Systems,
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