便携式流编码器收缩和增长

As companies launch small-form-factor encoders (SFFEs) for live streaming and (sometimes) recording, one of the biggest questions potential users ask is whether these devices offer the same encoding functionality as larger units.

The short answer is either “almost” or “yes,” depending on specific use cases. 在本文中, we’ll look at areas where four of these new SFFEs offer parity or enhanced features even while shrinking in size to fit in a messenger bag or even a pocket.

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在几乎所有关于sfe的讨论中, a number of questions about functionality arise centering on audio and video inputs and overall connectivity.

The miniaturization of these physical devices often means the companies have to decide which input and output connectors to accommodate. 考虑到其中一些设备比苹果电视还小, there’s only so much physical real estate on which to mount connectors.

The good news is that all of the units we reviewed have at least two input connectors, although the second input often pulls double duty with some other function for the SFFE.

Input

The alphabet soup of connectors ranges from CVBS to SDI to HDMI and analog inputs for both audio and video.

让我们从老式的东西开始:模拟连接器. 模拟视频输入的存在, 也称为复合视频消隐同步(CVBS), 是一种受欢迎的野外装备吗, since there’s never a guarantee that the user won’t need to fall back to an analog-only acquisition device. 也有模拟音频输入，通过1/8”(3).5毫米立体声连接器.

On the flip side, digital input options often meet or exceed those on a single PCI Express card. 例如, the availability of Serial Digital Interface (SDI) on some of these SFFE units means they can handle both interlaced and progressive digital content.

One of the units we reviewed for this article capped out at 3G-SDI, 哪一条HD-SDI链路能够处理2个.每秒97千兆位(Gbps)的串行数字信息. That means the units can capture 12-bit 1080p30 (progressive 1920x1080 at 30 frames per second) or 1080i60 (interlaced 1920x1080 at 60 fields per second) or 10-bit 4:2:2 10-bit 1080p60.

Every encoder we looked at has HDMI as a base digital input connector. In marketing terms, an HDMI input connector capable of 1080p60 could be either an HDMI 1.4或HDMI 2.0, but since none of the units we reviewed allow 4K capture, it’s likely that these are HDMI 1.4连接器.

Output

我们测试的几乎所有设备都有HDMI输出接口. 有些人需要这个连接器来进行设备设置, 而另一些则通过HDMI接口提供本地监控. Audio can be output over the same HDMI connector and, in some cases, via the analog audio connectors.

但并非设备上的每个连接器都能正常工作. 例如，在Epiphan Webcaster X2(图1)上， 现场测试的流媒体生产者), 该公司的网站指出 that “the AV, TF (SD card), and optical audio ports on Webcaster X2 are not used."

图1. Epiphan Webcaster X2(正面、背面和侧面)

On the 网work front, all of the devices have an Ether网 port for hard-wired connectivity. 我们推荐这种方法, because Wi-Fi can be notoriously finicky when it comes to trying to use the same Wi-Fi access point to send the origin stream and monitor the same stream coming back into the venue.

两个较小的设备, the Epiphan Webcaster X2 and the not-yet-shipping (as of mid-July 2018) Magewell Ultra Stream HDMI (下面的图2)，两者都有Wi-Fi连接. 只有Webcaster X2具有反向SMA连接器, 允许外部天线增强Wi-Fi信号强度. Ultra Stream还支持蓝牙连接, although it appears to be used only for initial setup and for monitoring the device during streaming.

图2. 尚未发货的Magewell Ultra Stream HDMI(正面和背面)

USB

每个设备至少有一个USB 2接口.0 port, which is required to hook up a keyboard, mouse, or combination of the two. Some devices have as many as three USB ports: one for a USB mouse, 一个是键盘, 第三个是各种测试版功能.

虽然有些设备有蓝牙功能, 其中哪些设备用于设置和监控, we suggest you follow this rule of thumb if you’re not intimately familiar with a specific SFFE: Carry a wireless mouse/keyboard with a USB dongle to connect for setup and other administrative functions. Connecting via a USB dongle allows both a mouse and keyboard to be used across a single USB connector, 释放任何额外的USB端口用于录制或其他任务, as well as avoiding any pairing or signal interference with Bluetooth.

This is especially helpful with the second generation of SFFE units, which eliminate all but one USB connector and use a microSD card for recording.