| ▲ | lifis 9 hours ago | ||||||||||||||||||||||||||||||||||||||||
Seems the classic legacy overengineered thing that costs 100x production costs because it's a niche system, is 10x more complex than needed for to unnecessary perfectionism and uses 10-100x more people than needed due to employment inerta. A more reasonable thing is to just use high quality cameras, connect to the venue fiber Internet connection, use normal networked transport like H.265 with MPEG-TS over RTP (sports fans certainly don't care about recompression quality loss...), do time sync by having A/V sync and good clocks on each device and aligning based on audio loud enough to be recorded by all devices, then mix, reencode and distribute on normal GPU-equipped datacenter servers using GPU acceleration | |||||||||||||||||||||||||||||||||||||||||
| ▲ | pjc50 8 hours ago | parent | next [-] | ||||||||||||||||||||||||||||||||||||||||
The sort of systems which demand 100% reliability tend to be like that. "Disruption" in the middle of live sports broadcast is unpopular with customers. | |||||||||||||||||||||||||||||||||||||||||
| ▲ | TD-Linux 8 hours ago | parent | prev | next [-] | ||||||||||||||||||||||||||||||||||||||||
While I think you are oversimplifying the timing issue, you are not the first to think that about 2110. | |||||||||||||||||||||||||||||||||||||||||
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| ▲ | jacquesm 8 hours ago | parent | prev | next [-] | ||||||||||||||||||||||||||||||||||||||||
Sounds like you've got it made then: produce the equivalent that fits in a minivan and laugh all the way to the bank. | |||||||||||||||||||||||||||||||||||||||||
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| ▲ | rezonant 38 minutes ago | parent | prev | next [-] | ||||||||||||||||||||||||||||||||||||||||
As someone who's spent a lot of time in this space and is quite interested in lowering the cost of entry and finding ways to simplify it, I'm afraid you've vastly oversimplified the problem. > sports fans certainly don't care about recompression quality loss... I think that's quite an assumption. In a modern video chain youd need to decompress and recompress the video from a camera many many times on the way to distribution. Every filter or combining element would need to have onboard decoding and encoding which would introduce significant latency, would be very difficult to maintain quality, and would introduce even more energy requirements than the systems we already deploy. High quality cameras aren't any good if they throw away their quality at the source before they have an opportunity to be mixed in with the rest of the contribution elements. You certainly wouldn't compress the camera feeds down to what you'd expect to see on a consumer video feed (about 20Mbps for 4K on HEVC). > normal networked transport like H.265 with MPEG-TS over RTP If you want to, you can do that already using SMPTE ST 2110-22 which loops in the RTP payload standards defined by the IETF. ST 2110 itself is already using RTP as its core protocol by the way (for everything). > do time sync by having A/V sync What do you mean by this? In order to synchronize multiple elements you need a common source of time. Having "good clocks" on each device is not enough: they need to be synchronized to the level that audio matches up correctly, which is much more precise than video as audio uses sample frequencies in the 48Khz-96Khz range, whereas video of course is typically just 60Hz. Each clock needs a way to _become_ good by aligning themselves to some global standard. If you don't have a master clock like PTP, your options are... what... GPS? I mean you _could_ equip each device with its own GPS transponders, but if the cameras cant get a reliable GPS lock then you're out of luck. > aligning based on audio loud enough to be recorded by all devices Do you mean physically? Like actual audio being emitted into the space where the devices are? Because some of the devices will be in the stadium where theres very very loud noises on account of the crowd, and some of them will be in the backroom where that audio is not audible. Then you need to factor in the speed of sound, which is absolutely significant in a stadium or other large venue. None of this is particularly practical. If you mean an audio sound that is sent to each device over a cable, well are we talking SDI (copper)? If so, we wouldnt use audio for that, we would use what's called Black Burst. But what generates the black burst? Typically, its the grandmaster clock. The black bursts on SDI need to be very precise, and that requires a dedicated piece of real time hardware. If you mean sending it over ethernet, you now need to ensure you factor in the routing delays that will inevitably happen over an open unplanned network. To deal with those delays, we typically do two things. One, we use automatically planned networks, where the routers are aware of the media flows going over each link, and the topology is automatically rearranged in order to minimize or eliminate router buffering (aka software defined networks, typically using NMOS IS standards to handle discovering and accounting for the media essences). | |||||||||||||||||||||||||||||||||||||||||
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| ▲ | amluto 8 hours ago | parent | prev | next [-] | ||||||||||||||||||||||||||||||||||||||||
> do time sync by having A/V sync and good clocks on each device and aligning based on audio loud enough to be recorded by all devices Why do you need good clocks? For audio, even with simultaneously playing speakers, you only need to synchronize within a couple of ms unless you need coherence or are a serious audiophile. If if want to maintain sync for an hour I suppose you need decently good clock. But as long as you have any sort of wire, basically any protocol can synchronize well enough. Although synchronizing based on visual and audible sources is certainly an interesting idea. (Audio only is a completely nonstarter for a sporting event: the speed of sound is low and the venues are large. You could easily miss by hundreds of ms.) > then mix, reencode and distribute on normal GPU-equipped datacenter servers using GPU acceleration Really? Even ignoring latency, we’re talking quite a few Gbps sustained. A hiccup would suck, and if you’re not careful, you could easily spend multiple millions of dollars per day in egress and data handling fees if you use a big cloud. Just use a handful of on-site commodity machines. | |||||||||||||||||||||||||||||||||||||||||
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