基准测试电脑, 捕捉卡, and Software Mixers for HD Capture and Streaming

When you’re producing a live event with a self-built, 以计算机为基础的系统, your focus narrows to a single relevant question: Is the system powerful enough to produce the streams required for the event?

为了找出答案, 我们组装了一系列(新旧)计算机。, 获得多个捕获设备, and downloaded multiple live streaming software programs. 然后我们做了多次测试, 流媒体到一个或多个流媒体服务, 录制各种格式的存档/ISO文件, 测量CPU利用率. 在windows系统上, we captured the results in Performance Manager and annotated the output to produce graphics such as those shown in 图1. On the Mac, we simply recorded CPU利用率 numbers during the tests.

Before discussing the results, let’s touch on testing procedure. First, to normalize the results, I used the same high-motion, high-detail AVCHD clip for all tests. 每一次, 我开始流媒体和/或录制活动, 触发录制的视频, 让它继续下去, 然后停止录制/流媒体. Then I changed the configuration and started again. To add a touch of complexity, I added a logo overlay to all videos.

I’ll detail each computer system and capture device used when reviewing the test results. For the mixing software, I used a prerelease version of Telestream Wirecast 7.1. I was glad I did, since CPU利用率 was down significantly from version 7.0，比版本6低很多.0. 我测试了vMix版本17.0.0.107和0版本.15.4 .开放广播软件(OBS).

让我们从笔记本测试开始.

笔记本电脑测试

I ran the first tests on an HP ZBook Studio G3 Mobile Workstation with a 2.8GHz Xeon quad-core (eight with Hyper-Threading Technology [HTT]) E3-1505M CPU with 32GB of RAM running Windows 10. The first capture device was a USB 3-based Epiphan AV.io 4K视频采集器.

图1(下面) details the results of tests run with Wirecast version 7.1, though tests varied slightly with the capabilities of the software mixer. 我从720p/2开始.25Mbps流到Facebook Live, and then added a 1080p/8Mbps archive encoded with x264, 将CPU利用率提高到55%以上. 通过比较，与Wirecast版本7.0.1、x264的CPU利用率超过70%. Test three was Facebook Live plus an archive encoded with the more efficient Intel Quick Sync Video codec.

图1. 2 .电视直播的CPU利用率.配备Epiphan AV的8GHz HP ZBook.io 4K视频采集器

根据经验, 一旦CPU利用率超过70%, you may start dropping frames in your live stream or recorded file. Though x264 exhibited slightly higher quality than Quick Sync, at 8Mbps the difference is very minor. If you notice that CPU利用率 is consistently exceeding 60% or so, 考虑切换到快速同步(如果可用) for your archive version.

Note that I used x264 when available for all live streams to Facebook和Ustream. If you find CPU利用率 uncomfortably high on your system, 考虑切换到快速同步(如果可用). I used x264 with the Very Fast preset since this was the default for all tested software programs. 我用中等预设做了一些测试, 但这使得CPU利用率飙升, 质量上的差别是看不出来的.

Wirecast also offers an ISO archive, which produces a Motion JPEG (MJPEG)-based QuickTime file. While about as efficient CPU-wise as the Quick Sync codec, the Motion JPEG file is more than 11 times larger (91.7Mbps as compared with 8Mbps), which could put a strain on the storage capabilities of your notebook. 稍后您将看到, 我还发现QuickTime MJPEG文件有点模糊, so I recommend using MP4 over MJPEG for the quality and file efficiencies. The final test involved sending 720p streams to two live streaming services, Facebook和Ustream, which required about as much CPU as Quick Sync and the ISO Archive.

关键的收获是什么? At 2.8GHz, E3-1505M Xeon系统，或2.8GHz i7系统, should have enough power to easily handle a 720p output stream, plus an archive version in x264 or Quick Sync formats. Slower versions of the same CPUs should deliver close to proportional performance, though the slowest CPU offered on ZBook Studio is a 2.6GHz i7, which should perform similarly to the tested model. 完全改变CPU, 比如双核i5(四核HTT), 完全改变了公式, 稍后我将简要介绍一个基于i5的系统.