Review: Harmonic ProMedia Xpress
的 Harmonic, Inc. Workflow System (WFS; created by Rhozet, (现在是Harmonic的一部分)是一种检索和编码音频和视频文件为多个单一文件和自适应格式的架构, checking their quality, 并将编码结果传递到本地或远程目的地. 主要的编码引擎是ProMedia Carbon(以前的Carbon Coder), 具有广泛输入和输出选项的瑞士军刀程序, excellent output quality, and many other fine features. 不幸的是，编码速度不是其中之一.
To remedy this, Harmonic recently released ProMedia Xpress, 一个高度集中的产品设计，以适应整齐地编码工作流程中使用的许多广播公司. Specifically, in its first iteration, 该产品只能使用MPEG-2或H输入MPEG-2传输流.264 codec, and it can only output H.264 encoded MPEG-2 transport streams, though with additional licenses, 系统可以将这些输出转换成块视频文件和HTTP Live Streaming (HLS)的元数据。, HTTP Dynamic Streaming (HDS), and Smooth Streaming.
而未来的Xpress版本将支持额外的文件输入，如AVI, MOV, and MFX input, including both ProRes and Avid DNx HD, output support will continue to be limited. For example, 尽管DASH支持计划在下一个软件版本中发布, the development path does not include single or multiple MP4 file output; if you’re an RTMP streamer, 要么使用ProMedia Carbon，要么寻找其他解决方案.
你可以花9美元购买纯软件版的Xpress,000; a rack-mounted turnkey system called the ProMedia 5200 application server, 哪一个 is the unit I tested, 花费25美元,000. 每个额外的自适应流媒体包格式的许可证是2美元,500, with an additional license of $2,500 for encryption for each adaptive format.
5200是一个庞然大物，有两台计算机. One serves as the controller; the other serves as the encoding node. Both are equipped with two 6-core 3.33 GHz Intel Xeon X5680处理器(24核HTT)， 12GB RAM, and run Windows Server 2008 RT Standard, SP1. 的 system does not use GPU acceleration, 两款设备都配备了Matrox G200eW显卡.
谐波公司开发的加速编码的技术被称为微网格并行计算, 哪一个, according to the marketing materials, “splits the large H.264 transcoding job into thousands of tiny ones, each of 哪一个 is completed concurrently, 消除与传统转码架构相关的瓶颈.” Xpress can operate stand-alone, 或者它可以作为一个编码引擎在谐波工作流系统, operating via a GUI or API. When you drive the system directly, 您使用ProMedia Xpress软件及其组件, 哪一个 run exactly like the Harmonic WFS.
Building a Workflow
图1 shows the Xpress Manager. As you can see, 界面顶部的选项卡提供有关活动作业的详细信息, queued jobs, pending QC jobs, and other functions. By way of background, all encodings are driven by a workflow, whether started manually, via watch folder or API.
图1. 的 ProMedia Xpress Manager.
You build a workflow in the Workflow Editor, 它使用在预置编辑器中创建的编码预置和在包预置编辑器中内置的打包预置. 图2 显示预设编辑器，您可以在其中配置自适应流并设置H.264 encoding options. 配置选项非常有限，包括H.264 configuration options. For example, all encoding is single-pass, 具有恒定比特率(CBR)和平均比特率控制选项, but not true variable bitrate (VBR). 这强化了最保守的适应性流理论, 但对于一些寻求比VBR更高质量的生产商来说，它可能过于缺乏灵活性, or even 2-pass CBR, often delivers. 如果你将碳编码器整合到系统中，你就可以得到这个，但这要以编码速度为代价. 的re will be more on quality later.
图2. 的 Preset Editor: Note that I’m editing the H.264自适应组，我将在下一个屏幕中部署它.
H.264配置选项仅限于配置文件和b帧间隔, 无法控制诸如熵编码或搜索函数之类的选项. In truth, for most users, fine control over H.264 encoding options is unnecessary; however, if you know what you’re doing, you may find this lack of control frustrating.
的 Package Editor performs a similar function, allowing users to configure HLS, HDS, 和平滑流选项，如块大小和封闭标题选项. express打包器可以集成来自多个源的标题, including CEA-608 and CEA-708, DVB Subtitle, and Teletext, 并转换输入，以便在所有三种打包格式中使用, 尽管一些定制开发对于完全集成可能是必要的.
一旦你有你的预设和包配置, 您可以在工作流编辑器中将它们构建到工作流中, shown in 图3. 组件有三大类(预转换任务), Transform Tasks, and Job End Tasks), 每个级别都有成功和失败组件. 你可以在中间的树形结构中看到 图3.
预转换任务包括需要Harmonic质量控制服务的质量控制或文件配置检查(不包括在内), or notification tasks. 转换任务是由预设驱动的主要编码功能. 在图3中，您可以看到我正在部署图2中创建的预设. 成功地将源文件编码为该预设后，Xpress将部署HLS和HDS包. 打包器输入在初始编码期间创建的MPEG-2传输流，并创建每个自适应格式所需的唯一容器格式和元数据文件. 由于不需要进行额外的转码，因此这些操作非常快.
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