流媒体设备买家指南

有时候你只需要一个小盒子. Perched firmly between software-based streaming encoders -- which run on laptops or desktops -- and higher-end video mixers -- which switch seamlessly between graphics and multiple video inputs -- there's a category of encoder products we call streaming appliances.

"Appliance" is a term for a product that is self-contained, often hiding the operating system behind a simpler interface. Some streaming appliances offer access to controls via front-screen tactile buttons or touchscreens, 而另一些则通过网页提供访问.

Streaming appliances often perform a simple task: encoding content to stream at predefined data rates via industry-standard codecs and formats. But a few offer additional benefits such as graphics overlays and rudimentary transitions.

在这份买方指南中, we'll consider a few key questions needed to determine whether a streaming appliance is the best choice. We'll also look at the options offered by streaming appliances.

输入的数量和类型

For a multicamera shoot, a streaming appliance is probably not going to pass muster. If, 然而, 你只需要一个视频源输入——比如说, from a single camera -- then a streaming appliance might make sense for your workflow.

电器有各种各样的输入, 包括模拟-复合, 组件, Y/C -和串行数字视频- SDI, HD-SDI, 3 g-sdi. A few streaming appliances even offer DVI or HDMI inputs.

在音频方面, inputs consist of analog unbalanced connectors (RCA) or balanced (XLR), and a few also offer captive screw connectors for bare-wire connections that minimize the size of the appliance while still offering multiple audio inputs.

The latter type of connector is often found on a new breed of streaming appliance, 它有内部缩放和多个输入, 可以选择哪一个在DVI之间切换, HDMI, 或串行数字输入. Note that this selection isn't true video switching, which takes advantage of time-base correction and a vertical interval switch to provide a seamless cut. The appliances with a selection option will show a momentary "glitch" when switched, and the codec will need to work hard to encode the glitch and resulting change of image.

图形支持

Streaming appliances don't have sophisticated graphics overlay capabilities, but a number of units can generate a graphic "bug" overlay in the bottom corner, 通过JPEG或alpha通道图像.

如果你的工作流调用, 例如, for multiple titles that need to be positioned over live shots of a number of presenters, 视频切换器通常是最好的选择.

The one other area where streaming appliances are gaining traction, 当涉及到图像, 虽然, is the ability to offer crawls along the bottom of the screen. 这个功能已经被添加到一些设备中, mainly from manufacturers whose target markets include education, as part of the safety and alert requirements for digital signage.

现场生产

许多流媒体设备都是“无头”设备, which means that they have no graphic interface beyond a 1-2 line LCD display. We've covered a few of these products in the past, noting that field production would require an external monitor, 鼠标, and keyboard to be able to make changes to even the simplest streaming parameters.

这些单位, 然而, 也可以通过网页界面访问吗, and a few have even added the ability to access and store basic parameters via Android or iOS device apps. The handset or tablet needs to be on both the same 网work and sub网, and most field locations where you use a streaming appliance won't allow you to open up ports in their firewalls just to access the controls for your appliance, so it doesn't hurt to carry a separate Wi-Fi access point (WAP) to allow access to the device. 如果您的WAP有以太网端口, 它可以放在同一个网络中, but check with the venue about its policies for "rogue" WAP devices before plugging a nonencrypted WAP into its 网work.