综述:着眼于低于2000美元的硬件H.264编码器

在过去的十年里，我用过各种各样的H.264编码器用于直播事件, typically conference events that involve one or more presenters and one or more computer screen inputs. The single biggest factor for my workflow is the available bandwidth on site at the event venue. 我需要一个H.264 that will get the best possible quality over a limited outbound pipe of 1–3Mbps sustained bandwidth. My goal for this article was to find the best encoder on the market for a wide range of live-streaming content, 从相对较小的运动，如说话的头到快节奏的运动. 我无法在所有类别中确定一个单一的“赢家”, but I could get repeatable results that you can use in your own research and comparisons for these and other encoders on the market.

我的典型管道使用第一代Teradek Cube 255, 在过去的5年里，哪一个一直很好地满足了我的要求. 我们已经进入了HEVC/H的黎明.265 technology—with very few economically priced encoders on the market—I thought now was a great time to compare the current stock of H.264编码器，价格低于2000美元. 当然也有更贵的编码器, but most of my clients need portability and lower costs to add livestreaming to their existing pipelines.

的竞争者

Among the wide variety of encoders available in the testing period for this evaluation, 我从四个不同的供应商中挑选了一个编码器, 每个都符合以下最低标准:

3G-SDI和HDMI输入
以太网/局域网连接
AVC / H.264编码器
Web-configurable接口
零售成本低于2000美元，适用的税收和运输成本之前

以下是每个编码器的简要概述，从最便宜到最昂贵.

Aja helo(1,295美元)

这个备受期待的进入H.264编码器 arena by AJA had some initial shipping delays, but was finally released in February 2017. 该编码器具有非常简单和紧凑的设计. 虽然它的外形尺寸在本次综述中排名第二直升机不是为安装摄像头而设计的吗. Its rack-mountable design makes it a compact addition to an existing footprint for a more permanent A/V rack. 所有的视频输入和输出插孔, audio, 网络, 电源在底盘的背面, while more user-friendly push controls to enable recording and streaming and USB/ SD card recording media are on the front side. 您还可以为编码器存储多个预设和配置文件, 使从一个配置更改到另一个配置的速度更快. While the 直升机 doesn’t have a form factor designed for portability or mounting as nicely onto a camera as the Teradek Cube 655, 您可以购买单独的电源适配器，从流行的电池类型运行直升机.

直升机在网络上的可发现性相对简单. 如果你使用的是Mac或bonjourl支持的设备, 直升机的地址将于周日公布. 如果你有Safari浏览器, you can enable Bonjour discovery and quickly navigate to the web configuration page for the 直升机. 如果您没有启用bonjourn的设备或浏览器, you’ll need to use the AJA eMini-Setup application on a laptop or desktop computer to discover the 直升机. This application will report the IP of the 直升机 so you can configure the device in a web browser.

直升机的缺点很少，但值得注意. The 直升机 requires all configuration to be done within a web browser user interface; there is no display and/or input control on the unit itself. 像这样, you need to make sure all your configuration data is in place before you start to stream, 除非你手边有一台笔记本电脑可以连接到与直升机相同的网络. 不过，令人欣慰的是，直升机的网络界面非常快. 更改几乎是即时的，不需要费力地重新启动硬件.

The current firmware doesn’t seem to support B-frame encoding (available in Main and High profiles of AVC / H.264)非常好，至少对于典型的RTMP推送到流媒体服务器. 最后, the output audio sampling rate is fixed at 48KHz; there is no option for using a different output sampling rate.

Matrox monarch HDX(1995美元)

我熟悉Matrox的Monarch系列已经有一段时间了, 并且使用了hdmi版本的君主HDX 在很多场合. matrix有几款Monarch车型. The HDX came in just below the $2k price point, and it features both SDI and HDMI inputs. 就像美国航空公司的直升机, the 君主HDX is designed to be installed in a more semi-permanent A/V rack system for routine and regular streaming in a venue.

On the 君主HDX’s back panel, you’ll find all A/V inputs and a plug for the unit’s power cable. 在前面, 您将找到启动和停止流媒体的控件, 以及两个USB接口和一个SD插槽用于录制媒体.

Discoverability of the 君主HDX requires the Matrox 君主HDX Utils application, 哪个报告IP地址, 设备名称, 序列号, 固件版本, 以及您网络上每个君主HDX的状态. 一旦你知道了君主HDX的IP地址, 你可以在网络浏览器中使用该地址登录并配置你的流.

君主HDX, 比如AJA 直升机, can only be configured with a web browser and not with a built-in menu display and option controls. The Monarch’s web interface is slower to update the unit with new settings than the 直升机’s. The HDX is the only unit tested that has an audible fan running anytime the unit is powered on.

鱼鹰爪g2贡献编码器($1,890)

这篇综述提供了我第一次测试鱼鹰H的机会.264编码器，我的研究开始于第二代，或者 G2,爪在预发布中. Talon G2的外形与Teradek的Cube系列类似. 而在魔爪G2上没有三脚架或相机支架, 它的外形足够小，可以放进相机包里. This unit was the only one that could also encode from an older RCA-style video input/signal, 除了HDMI和SDI端子.

Because the Talon G2 has a built-in touchscreen that displays the unit’s acquired IP address after booting, 不需要发现工具来配置设备. 魔爪G2的网络配置不像直升机那样快速响应, 但是所有必要的视频和音频压缩设置都是可用的.

Teradek cube 655(1990美元)

本综述中测试的最后一个单元，也是最昂贵的，是 Teradek Cube 655. Teradek是第一批引入低成本H.264 encoding hardware, and the Cube 655 improved on earlier models such as the Cube 255. The Cube 655 is designed for portable use; accessories allow you to mount the Cube directly onto a camera’s hot shoe or a tripod screw. 而Cube 655没有内置电池, you can purchase adapters that enable you to power it with popular battery types from Canon, 索尼, 日本胜利公司, 松下, 鲍尔和安东/.

就像美国航空公司的直升机, the Cube 655’s web configuration page can be auto-discovered by Bonjour-enabled browsers such as Safari. Cube 655的最大特点是内置显示屏和操纵杆, which can be used to configure nearly every option that’s also available in the Cube’s web configuration pages. The Cube’s display can tell you the IP address of the encoder if you want to configure the unit with a web browser. If you want the flexibility of changing encoding or 网络 options without the need for a device that’s connected to the same 网络, Cube 655可能是您的正确选择.

测试过程及方法

It’s relatively straightforward to run qualitative metrics against various renditions of a video-on-demand (VOD) file. 这样做, 您只需获取一个高质量的源文件, 用不同的压缩设置进行编码, 然后比较结果. 然而，使用直播流，这个过程就有点复杂了. 每一个小时.264 hardware encoder needs to receive the same input signal and record the compressed output to a file. 因为并非所有测试的编码器都可以记录到本地附加的存储驱动器, I had to come up with a system that recorded outbound compressed streams over the 网络.

减少网络变量, 我在MacBook Pro上安装了Wowza流媒体引擎, which has a solid state drive (SSD) that easily records live streams without any disk I/O issues. 在同一个本地网络中，我连接了每个H.264编码器. 对于源内容，我从4ksamples下载了高质量的4K内容.并缩小到Apple ProRes HQ 1080p29.97帧/秒. 使用Telestream开关和Blackmagic设计ultraststudio迷你监视器, 我通过SDI将ProRes版本输出到Convergent Design Odyssey7Q+. 内容记录在高生产质量, 我可以通过SDI始终如一地重放相同的剪辑到每个编码器.

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