10 Best Practices for 在线直播 Production

甚至当所有的内容, talent, 相机, 照明, 音频也算出来了, live streaming event production is far from over. The workflow to get the signal from the camera to the viewing audience can make or break the production.

There’s no single solution that fits all budgets and types of events. But in this article I will review some of the best practices and tips to make sure your live event streams go off without a hitch. I’ll cover some 信息 that should be useful to beginners but hopefully more advanced producers will learn something new as well.

These tips come from interviews with industry experts, discussions from panels I’ve moderated at 流媒体 conferences, 还有我自己的经历.

1. 做这件事的方法不止一种

首先，一个警告. 没有一种方法可以做到这一点. 实际上有数百种. The perfect solution for one event might not make any sense for another.

“不要把自己限制在单一的工作流程中,迪伦·阿马贾尼说, who works in digital workflow technologies at Viacom, “and get to know the tools and technology that’s at your fingertips.”

With all the encoding and transmission options now available, Armajani says “you really can stream live from just about anywhere in the world on just about any budget and at least have your content show up online. The challenge really becomes weighing the cost vs. 质量和. possible points of failure and determining what workflow is optimal for your show.”

2. 使用视频切换器

Let’s start with the signal coming out of the camera. The best practice is to use multiple 相机 and a video switcher to create a visually interesting, 动态显示.

When selecting a switcher, don’t underestimate the number of inputs you will need. Even though you might only use two or three 相机, 您可能需要许多额外的输入, 例如来自舞台展示的图形, 动画背景, 额外的GoPro相机位置, 视频播放源.

Because there are so many switcher options available and diverse viewpoints, it’s beyond the scope of this article to make individual recommendations. The best switcher for any project is the one that offers the features you need within your budget. Perhaps more importantly, it’s the one you are most comfortable using.

Video switchers can be divided into two basic types: hardware-based switchers that run on dedicated boxes with their own control surfaces and software-based switchers that run on a desktop or laptop computer with video capture cards or converters.

Software switchers cost less and can deliver a flawless production. Yet many producers, including Adam Drescher, co-founder of the video production company 套件现货，更喜欢硬件切换器.

“There is something great about directing or TD’ing a live event and feeling the buttons and responsiveness of a hardware switcher,他说. “Also, there’s no chance of a software crash interrupting the event.”

Drescher used a NewTek Tricaster to produce this year’s Westminister Kennel Club Dog Show, switching between a camera at each of the 12 different rings to create a single program output. The camera at each ring was also hooked up to an encoder to generate 12 single camera feeds, giving viewers the ability to become their own technical director.

套件现货’s Adam Drescher uses a NewTek Tricaster to switch among 12 camera feeds at this year’s Westminster Kennel Club Dog Show.

3. 硬件或软件编码

At some point you need to encode the video into a streaming format. While this usually happens at the event venue, we’ll see some examples later of how it can be done offsite. 就像转换者一样, there is a large range of hardware and software encoders, as well as some switchers that also do software encoding.

在一端, 有免费的编码器软件, 比如Adobe的Flash Media Live Encoder, 在PC或Mac上运行的软件. 转播画面, Ustream, and YouTube also offer free encoding software to stream to their own services.

Next up are software encoders such as Telestream’s Wirecast Pro or CombiTech’s VidBlaster, which can also be used as switchers and sell for less than $1,000. 用软件编码, 就像软件切换者一样, you need capture cards built in to the computer or external converter boxes to get the video signal into the computer.

With hardware encoders, you just plug your video signal in. At the top of the line are hardware encoders made by Elemental, Cisco, Haivision, 尼亚加拉, 和数字激流, 价格在10美元之间,000元及50元,000.

With 15 years of experience delivering live video on a global scale, 克里斯-曼, 高级数字媒体经理 Yahoo, recommends hardware encoders like the Elemental Live. He says “software-based encoders are inherently less dependable than hardware encoders.” Another benefit is “the ability to push more streams out of a more powerful box.”

All of these encoders are capable of delivering a flawless webcast, but none is perfect. “Every single product in the market fails at some point or other, 即使是最昂贵的编码器,奥尔登·费蒂格说, Ustream的客户成功总监. “I’ve been on the phone with people when their $40,000编码器看起来不太好, 或者他们不知道如何操作它, 或者需要重新开始. 最好的系统是你所知道的, 你已经广泛测试过的那个, and is stable in that environment with those inputs. For some that’s a hardware encoder, for others it’s a software encoder.”

4. 需要编码和分发多少流

Life would be simpler for live event streamers if there were one universal format and bitrate to encode and distribute in. That’s the goal of MPEG-DASH and technologies like it, but we are not there yet. For now, many streams are needed to reach viewers with different connection speeds and different screens.

在会场, one option is to encode at a single high bitrate stream that gets transcoded to many renditions in the cloud.

Mangum says if you are going with the single stream approach, “a 1280x720 frame size feed encoded at 4Mbps would be a good starting point.“对于音频部分, 他建议160Kbps的音乐活动, 但是“如果你在编码一个会说话的脑袋, you can drop audio down to 96Kbps and it will still sound good.”

This single stream would typically use the RTMP Flash Streaming protocol, the H.264 video codec, AAC audio codec, and progressive frames.

Streaming services can take this single stream and transcode it in the cloud to support RTMP, HTTP和HLS流, 所以它可以在电脑上观看, 移动设备, tablets, 还有机顶盒. Streams are typically rendered in the cloud into four bitrates and frame sizes ranging from HD quality to a lower mobile setting.

Another option is to generate multiple streams onsite. This requires those more expensive encoders and a lot of bandwidth. 但是,正如转播画面 co-founder and CEO Max Haot says, “the upside is the quality is higher since you don’t re-encode.”

Elemental Live encoders in action at the X-Men: Days of Future Past red carpet event in New York, 2014年5月. 友情提示Natália Tanus

5. 发布视频

One of the most important and potentially challenging decisions you need to make is how to backhaul or get the video signal from the live event venue to a remote streaming server. Using the public internet bandwidth is the most common and cheapest approach, 但其他选择包括使用卫星, fiber, 或者蜂窝技术.

“We generally stress that success for a live event is based on both solid bandwidth and rehearsals,Drescher说.

If you use an internet connection, use a wired connection rather than rely on Wi-Fi. Test the bandwidth using a website such as speedtest.net. But a pre-event test can be misleading if you’ll be sharing bandwidth with an audience that hasn’t arrived yet.

“The biggest challenge for preparation is testing the internet in advance, making sure it’s dedicated so that attendees at the event don’t use all the bandwidth,哈特说。.

Bandwidth for the live stream can and should be dedicated and separate from any bandwidth used for the audience and the stage production. Requesting and confirming this with the on-site IT staff is a must.

那么，你需要多少带宽呢? A good rule of thumb is two times the target bitrate for all the encoded streams you’ll be generating. Most encoders use variable bitrate encoding, which spikes over the target bitrate.

“10Mbps的高清上传, but even with less than 1Mbps up you can get a great stream out if you choose the right quality and test,哈特说。.

“如果你有1或2Mbps的连接, 你仍然可以做流媒体, 但我可能会跑80公里, 640 x 360 stream and don’t try to push HD content out a weak connection,费蒂格说. 虽然高清质量是一个伟大的目标, there is no point to pushing a choppy HD stream if your bandwidth only supports 1 frame per second.

When no internet bandwidth is available, another option is to use cellular bandwidth. Teradek and LiveU are among the companies that make portable hardware to transmit an encoded stream over wireless cellular networks such as 3G/4G LTE and WiMAX. For increased reliability, these systems use multiple modems on different networks. Testing can be tricky because the bandwidth available before the event will be different when the audience arrives.

Another backhaul option, usually the most expensive, is to use a satellite truck or video fiber. This is the way TV broadcasters usually transmit remote feeds, but it’s being adopted more and more by live webcasters for high-profile events. 使用这种方法, video is encoded for the web at the satellite downlink facility or on the receive end of the fiber connection, 不在会场. While these transmission methods are extremely reliable, they too can fail.

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