全在NDI上
齿轮的优点
我是TriCaster的用户. 我也使用vMix. 对于我的工作流程, one thing that would be a lot more expensive and difficult to do without NDI is wireless video. 最近，我被邀请直播一个TEDx活动. They hired me just a few days before it occurred because it had sold out and a lot more people wanted to see it. The TED organization has published video guidelines on how TED events should look and sound (and everything else as well). 其中包括应该使用多少台摄像机, 它们应该在哪里, 以及镜头应该是什么样子. And while the guidelines refer to five or more cameras providing a variety of shots, this event had only two—a front camera and a second camera just to the side of the main one.
There was no back-of-the-room camera showing the whole stage and no camera from behind the presenter to provide a view of audience involvement. 活动的早晨, I added a wireless router and two small cameras that provided me with two additional views, 有两倍的摄像机来进行拍摄. I ran no wires, and I was able to call both devices up as NDI devices over the wireless network.
此外，我还使用了NewTek Connect Spark (下面的图4)拍摄投影片. 因为它被放置在音频混音器旁边(离我150英尺), 我也用它来摄取事件的音频. 火种还能无线传输, I ran a wire because I wanted to make sure it couldn’t be interfered with by some rogue wireless system. Wi-Fi的缺点是不是ipad 2的专属.4-GHz or 5-GHz spectrum, and there are other systems that can essentially knock out Wi-Fi when used. 有线连接提供了更高的可靠性. 我的两个主要相机是SDI, so the two wireless additional cameras were not essential to the coverage of the event. 重要的摄像机是用电线连接起来的.
图4. NewTek Connect Spark
Another advantage of an NDI workflow is that it enables you to use a single piece of gear for multiple purposes. 例如，BirdDog转换器(下面的图5)是双向的. 它们可以用在相机上提供视频、音频、计数、coms等. Or, if needed, you can go into the settings of the device and make it an NDI receiver instead. Then you can have it at the stage receiving the PowerPoint slides for monitors that are at the foot of the stage for presenters to see. Because NDI video is just data, routing any source to any destination on the network is possible.
图5. BirdDog Studio NDI
You can even route a single source to multiple destinations without needing a video distribution amplifier or splitter. 它只是数据包, 所以没有信号丢失或中断，如果一秒钟, 第三, or 33rd device listens to those packets or uses them to display the program audio in screens throughout a venue, 校园, 或事件. But then you need to put on your new “networking professional” hat and be aware that the more packets you send around, the more you increase the total amount of data passing through the network and the more bottlenecks can occur depending on the scale of the gear being used. Another case in point: The GM Financial setup uses the three 4K Panasonic camcorders.
内置的NDI是NDI|HX，它是NDI的低比特率版本. There’s also a full NDI, which is implemented in hardware on converters like those from BirdDog. 这些全ndi转换器具有更高的比特率和更低的延迟, 在某些情况下，哪个是重要的, like a live show in which the video will also be displayed on the screens next to the stage, 通常称为图像放大(IMAG). 在做image的时候, 您希望从相机到屏幕的延迟最少, 完全NDI提供了这一点. 想象一下，你有四台使用4K NDI的4K相机, 然后向屏幕发送4K NDI节目, 都通过以太网传输. 通过NDI的单个4Kp30流可以达到280Mbps. 一个4Kp60的数据流可以将速度提高到480mbps——对于一个摄像头来说. 添加第二个摄像头, and you’ll have completely saturated the typical gigabit network available in most places. 你需要一个10g的网络基础设施, 至少, 可靠地处理4Kp60的multicam事件.
即使是高清也会带来网络挑战. Consider the 校园 I mentioned earlier that wanted to deploy NDI everywhere: If it added 12 BirdDog PTZ cameras doing 1080p60 full NDI, 这将使每个摄像机的网络负载增加约200Mbps. 你只是加了2.4 gigabits of traffic to what’s likely to be a 1-gigabit network already full of data trying to get through. 正如我在我的 移动Multicam成功的7个规则第一条规则是“自带好的Wi-Fi”.“从本质上来说, this means your video network needs to be separate from everything else so that it has the bandwidth to pass the traffic with ease. 没有瓶颈.
现在, 不可否认, 如果一个特定的设备没有被寻址和“接收”,“那么它就不会主动将视频流传输到任何地方, 而且12个摄像头的总带宽在任何给定时间都要低得多. But if two conferences are in session and you have just three cameras in each room—plus one device capturing slides and audio—and they’re all sending video to two mixers, 然后是两个房间，每个房间有四个设备. 有8个设备以200Mbps的速度发送视频，你将传输1个.6千兆位的数据在项目开始前还没有在网络上.
不是每个PTZ都有这样的数据速率. NewTek的PTZ相机, 例如, outputs 1080p30 video using the lower-bitrate NDI|HX flavor and tops out at 20Mbps. In a huge deployment, that’s a good reason to use lower-bitrate (and longer-latency) NDI|HX devices. Not every camera is going to have the same exact bitrate, as each may encode slightly differently. It’s important to be aware that the type of NDI affects your total bandwidth needs, 您的网络硬件可以处理什么, 以及完全NDI与HX的注意事项.
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