The Big Sevastopol Officers' Ball traditionally takes place in June, but this time the preparations were not successful. The organizers decided to launch the Sevastopol Ball Online. Since we have been broadcasting the event for several years in a row, there was nowhere to retreat. Viewers on Facebook, VKontakte and YouTube, 35 couples are dancing at home.
In general, while doing online broadcasts for some time, we noticed a trend that almost every project requires (or we demand from ourselves) some kind of innovation. Either we use SDI for the first time, or a video sender, or we transmit a signal using several 4G modems from the sea, a new remote control, a signal matrix, pick up video from a copter, restream to 25 VK groups, and the like. Each new project makes you plunge into the world of streams even deeper. We talk about it on YouTube VidMK, we decided to write on Habr.
So the task...
The dance ball is being held online due to the epidemic. There is a leading couple, the rest of the participants dance, repeating after them, that is, they must see and hear the main couple along with the music.
At the beginning, the governor of Sevastopol joins in to open the ball. The finished staged broadcast goes to YouTube, Facebook and VK.
The most obvious way was to call everyone in a video chat. Zoom was the first to come to mind, but I usually try not to immediately grab what is on my lips, but look for alternatives. Maybe they have great marketing, and even if the tool is good, there is surely something else. TrueConf was mentioned several times in the AVstream chat, so I decided to give it a try.
It is important to say here that we are in the Crimea and many popular services do not work here. You have to look, and often alternatives are better. So, for example, instead of the blocked Trello, we started using the powerful Planfix.
TrueConf immediately bribed me with the opportunity to raise my server. In theory, this would mean that we are not dependent on the overall increased load on data centers during the period of self-isolation, we sit quietly in Sevastopol, connect mainly local users and a few from other cities, and everything works stably. In addition, using your own server was more profitable in terms of money. And in the case of our customers, they also gave it free of charge, since the organizers of the NPO ball had it.
In general, we tested the product and realized that it suits us. Although we did not do a full load of 35 people during the tests, it was a bit scary how an old computer would behave as a server. The requirements for the system unit are quite high under such a load, so they dragged a computer based on AMD Ryzen 7 2700, it became calmer with it.
The server was physically located in the same place where the broadcast of the ball took place. The main video communication application was connected on the same network as the server. This added confidence that the picture would definitely get to the server, and only then go online to the rest of the participants. By the way, the Internet should be good. For our 35 participants, the upload speed reached 120 Mbps, that is, the usual Internet of 100 Mbps will not be enough. In general, the server is working, let's go on air ...
Camera signal
Any video chat prompts you to select a webcam as an image source and a microphone for sound. What if we need to get a professional video camera and sound from two microphones with a phonogram? In short, we used NDI.
We had to direct the entire broadcast and stream it on social networks. To do this, we had a main computer in the role of a mini-OBT (mobile television studio). All work was carried out using the vMix program. This is a fairly powerful software for organizing broadcasts of various types and levels of complexity.
Our dancing couple was filmed by one camera, there was simply no need for more. We captured the camera signal using the internal BlackMagic Intensity Pro card. In my opinion, this is an up-to-date card for capturing a single HDMI signal. This signal had to be sent as a webcam to TrueConf. It was possible to immediately convert the stream to a webcam using vMix, but I did not want to pile everything on one computer. Therefore, a separate laptop was used for the trueconf call.
How to get a signal from a camera on a laptop? You can create a virtual video signal on one computer and catch it on any other computer on the local network as many times as you like. This is NDI (Network Device Interface). In fact, a kind of virtual cable that does not need to be particularly cunningly administered. The width of one stream for 1080p25 is almost 100 Mbps, so for stable operation you definitely need a 1 Gbps network or more than 150 Mbps Wi-Fi. But cable is better. There can be many such NDI signals in one local network, as long as the channel width is enough.
So, on the main computer in vMix, we see the signal from the camera, we send it to the network as an NDI signal. On the caller laptop, we catch this signal using the NDI Virtual Input program from the NDI Tools package (it's free). This mini-program creates a virtual webcam into which you plug in the desired NDI signal. In fact, our HDMI camera via NDI appeared in TrueConf.
What's the sound?
We collect the sound from two radio microphones and the phonogram using a good audio console and start it with an external audio card in vMix. It is this audio sum that we send to the air and to our NDI stream for the trueconf. There, instead of the laptop microphone, select NewTek NDI Audio. Now all our dancers see and hear our beautiful picture and high-quality sound in a call.
Essential picture
TrueConf chose the usual calling mode, when everyone sees everyone. There was also an option when we see everyone, and everyone sees only the presenters. This is more efficient, but then there would be no mass effect.
In the βeveryone sees everyoneβ call format, you can choose any window that you want to make large. So the participants saw the leading pair, and we created another user, from whose account we broadcast the image and switched between pairs. We clicked on the right pair and enlarged their screen, the rest of the pairs were small at the bottom. Sometimes all screens were displayed to show how many people were dancing in sync.
Now about synchronicity
You must have wondered about the delay. Yes, it was, about 1-2 seconds in both directions. Here we have music playing, the sound comes to the participants later, they dance to this rhythm, and their image returns to us even later. We decided to neglect this within the framework of the format, and it still looked large and interesting.
You can solve the issue of synchronization for viewers by artificially delaying the sound on our air for social networks. Then the viewer of the stream would see how the participants dance exactly to the rhythm of the music. But not the fact that the image from all comes with the same delay. This is another complication of the ether scheme, we will definitely do this next time.
By the way, there is another mini-program in the NDI Tools package - Scan Converter. It creates an NDI signal by capturing your screen or webcam. This is how easy it is to organize broadcast, for example, cyber competitions within a local network, having only this network and webcams. No more devices needed.
For us, it was another project where we had to try out new solutions that we had not yet encountered in combat streams. I will be happy to answer all your comments, carefully and with interest I will study the wishes and recommendations, if you know how it could be done better. The world of streams is endless, many technologies appear before our eyes and we can learn together faster. Below you can watch an overview video from the site.
Source: habr.com