回顾:Kulabyte XStream Live 2.1

如果你正在制作一个直播活动, you have three choices when it 和es to encoding: You can hire out the work, 购买一个流媒体设备, 或者构建自己的流编码器. If you choose the third approach and want to stream HD H.264 video via Flash, Kulabyte’s XStream Live 2.Flash视频编码器需要在您的短列表上. While the interface is still (to put it kindly) a work in progress, the encoder proved very efficient and reliable and produced excellent video quality.

让我们从速度和信号开始. The software costs $6,495 per server with no CPU core limitation. It can use FireWire input for SD streams and is 和patible with input cards from both 德高望重 and Blackmagic Design for HD. 我用的是Blackmagic DeckLink HD Extreme进行测试.

作为概述, Kulabyte’s software includes a feature called the Preset Maker and the XStream Live encoder, which can produce up to four simultaneous streams if your 和puter is sufficiently powerful. 操作上, 首先创建预设, 在事件设置期间将其加载到编码器中, and then press the magic Start button to start producing the stream. 创建预设时, 指定目标服务器, 流的名字, and other details; you can choose to save an archive file during the event.

创建预设
Kulabyte’s Preset Maker (图1) is a very spare application that deals more with stream and connection issues than preprocessing and encoding parameters, 虽然这可能会在未来的版本中改变. You can create a preset with up to four outputs of varying parameters with the multiple files available as source files for dynamic streaming in a live event scenario. 对于每个输出, you can designate both a primary and a backup stream—a nice bit of redundancy that lets you seamlessly switch to the backup stream should you encounter any problems with the primary.

Blackmagic integration within the Preset Maker wasn’t quite 和plete; for example, the HDMI input that I ultimately used for my testing wasn’t available as an Input Type option. To make it work, I had to modify the XML code in the preset itself. 除了, most preprocessing and encoding options are not presented in the Preset Maker, so you’ll have to modify them (if necessary) via XML as well (图2). 幸运的是, the product manual does a nice job defining the text strings for all relevant options, 虽然你不会说这个界面很简单, 这当然是可行的.

Kulabyte使用MainConcept H.264编码器，在我所有的H.264编解码器比较. It exposes a wonderful range of advanced encoding parameters, from entropy encoding techniques to enabling pyramid B-frame encoding and setting quantization values for I-, B-, 和P-frames. Still, if you’re the type who likes to tinker with advanced H.264的设置，你最好钻研你的XML.

Video input controls will depend upon the capture card you use, with none available for FireWire. 用黑魔法卡, I had to set inputs and other preferences in the Blackmagic Control Panel and then set them again in the Kulabyte Preset Maker. It’s been a while since I’ve added an input card to a 和puter, and it took a while to get all the inputs and outputs configured and working properly. 没有繁重的, but you should budget plenty of time for installation and shakeout before your first live event.

I installed the Blackmagic card and Kulabyte Encoder on a 3.0 GHz Quad-Core HP xw4600 workstation running Windows XP with 3GB of RAM. To test the live output, I installed a trial version of the Adobe Flash Media Server 3.5对3.2 GHz Quad-Core Z400 HP workstation running 64-bit Windows XP with 6GB of RAM. 做完测试后, 我希望我在Z400上安装了编码器, 如果不是八核的nehalem Z800的话. Though I was able to produce two streams simultaneously without problems on the xw4600, you’ll almost certainly need an eight-core system to produce four simultaneous streams.

Once you’ve created your preset and created and configured your video input, 你已经准备好开始流媒体了. 运行Kulabyte XStream Live应用程序, 加载预设, 开始视频输入, and click the Start button; the encoder will then start pushing the streams. I started by testing a single stream produced at 720p parameters at 2,200Kbps. 但在与Kulabyte代表讨论后, I switched to encoding two simultaneous streams to match the product’s most 和mon usage in the field. 在这些测试中，我产生了一个960x540 H的流.264 video at 1,300Kbps and the other at 640x360 at 840Kbps.

一旦开始编码, 状态灯显示主设备的状态, 二次, 存档流, 而一个音频计在左边反弹, confirming that you’re streaming audio with your video. 在右下角, 程序显示当前的CPU使用情况, 如果接近100%，哪个对监控至关重要, 它可能会中断流. 如果发生这种情况, 您可以禁用流并单击“更新设置”, 服务器将停止该流. It’s a pretty drastic measure that you should be able to avoid with pre-event testing, but it’s nice to know that it’s an option should CPU utilization unexpectedly rise.

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