A Buyer’s Guide to Live Encoders
All live events start with an encoded stream produced by a live streaming encoder. In this guide, I’ll discuss the categories of live encoding products and identify the factors you should consider when buying an encoder.
How Many Streams?
Let’s start with three preliminary items. First, before you start shopping, you should identify the number of streams that you’ll deliver and the formats you’ll deliver in. For small producers, this might be a single stream H.264 stream delivered via Flash to desktop viewers. For a large producer, this might mean multiple adaptive groups of streams delivered via Flash to computers and HTTP Live Streaming (HLS) or Dynamic Adaptive Streaming over HTTP (DASH) to various mobile and over-the-top (OTT) platforms.
Once you’ve defined the streams, identify the features incorporated with the streams, by which I mean features such as captioning, advertising insertion, and digital rights management (DRM). Note that if you need features such as these, your universe of potential encoding candidates shrinks dramatically, since very few encoders -- mostly in the expensive, big-iron category -- support them.
Your goal should be to create a list of streams, formats, and features. This is fundamental to your buying decision, and you should resist the urge to start shopping until you know exactly what you’ll be delivering.
Where Will You Produce Them?
Next identify the schema you’ll use to produce the streams. The traditional approach was to produce all streams on-site, which for very large events required one or more very robust hardware encoders and sufficient outbound bandwidth to transmit all the encoded streams out of the building and to the content delivery network (CDN) or other distribution mechanism. This schema is still used by many large producers today.
Another approach is to create a single set of streams on site, and transmit them to an external server or service that can transmux the streams into multiple formats to serve different platforms. The on-site encoder might produce six streams formatted for delivery via RTMP-based (real-time messaging protocol) HTTP Dynamic Streaming (Flash) and transmit them to a streaming server. That server could then reformat the H.264 streams into the MPEG-2 transport stream and create the metadata files necessary for HLS delivery to iOS, Android 3.0+, and most OTT devices. This approach produces fewer files on site, so it reduces the on-site encoding requirements and the concomitant outbound bandwidth necessary to deliver the files to the distribution servers.
Still, a third approach is to create a single, high-quality stream on site and transmit that to a server or service that can transrate the stream into the multiple streams required for adaptive delivery. Unlike transmuxing, which involves only changing the container format and producing metadata files, transrating involves re-encoding the input streams into multiple files, which is much more CPU intensive. Once these files are created, the service or server can transmux them into the formats necessary for delivery to different platforms. Obviously, this approach reduces the on-site encoding and outbound bandwidth requirements even further, making it a favorite of smaller producers, and often the only cost-effective schema for delivering adaptive streams from a bandwidth limited facility. For these reasons, this approach is becoming increasingly popular and is the approach taken by YouTube Live and Brightcove, Inc.’s Video Cloud Live service.
Basically, before you start shopping, you need to map out the overall encoding schema you’ll use to produce the streams so you can define your on-site encoding (and outbound bandwidth) requirements. If you’re implementing advanced features such as adaptive streaming, DRM, advertising insertion, or captioning, make sure that every product or service in the workflow can support the required features.
Once you’ve identified your on-site encoding requirements, you can go shopping. For the rest of the article, I’ll walk you through the different classes of encoders and discuss how to differentiate products within each class, starting with hardware encoders, then moving to software.
One issue I won’t discuss is quality, which all vendors quite naturally claim is the best available. While I haven’t tested all the products that I’m discussing, I’ve tested quite a few, and the quality is generally relatively uniform. So you should assume that the quality produced by all contenders is equivalent, and focus on the other features identified later.
When evaluating hardware encoders, one universal consideration is to make sure that your encoder connects with your video production gear, whether you’re using a single camera or a production mixer. While there are multiple format converters available that can convert formats ranging from HDMI to HDSDI, it’s always easier if you can directly connect. Beyond this, the first step is to choose the category of product that you’ll need to buy, and then how to distinguish products within the category.
I call the first hardware category big-iron encoders, because it typically includes high-density units designed for rack-mounted installation that start at about $5,000 and range far higher. Often products in this category are the only option when you must produce multiple streams and/or multiple formats on site. Since this is the class of product used by many broadcasters, most products will support features such as multiple-format DRM and captioning, as well as advertising insertion and Commercial Advertisement Loudness Mitigation Act (CALM Act) support (and the European equivalent).
Key considerations in this class include the number of units necessary to support the required outbound streams. This impacts the initial capital expenditures (CAPEX), of course, but also ongoing power and storage costs, maintenance, and the price of creating a redundant system for failover, if needed.
Also check whether the unit will be upgradeable to H.265, as some lower cost systems use dedicated H.264 encoder chips that can’t be upgraded. While live H.265 probably won’t be important for most producers until 2015 or beyond, big-iron encoders typically cost so much that you should know the status of this feature before making a buying decision.
Another factor that entertainment facilities might consider is the ability to output a stream or streams to a CDN for external delivery, while supporting internal playback. For example, DVEO offers the MAGNUS Anytime system that combines live encoding functionality and a streaming server to enable multiple screen delivery both inside and outside your firewall. This type of system would be ideal for stadium and event producers who need to supply streams to external viewers over the internet, and also internal viewers.
Portable encoders are hardware devices designed for portable operation, with controls ranging from on-board status lights to a touchscreen LCD panel. Most portable encoders enable one-button operation that’s ideal for nontechnical users. For example, your technical staff can create and choose encoding presets and enter server credentials in the office, and you can send your sales or marketing team out with the unit for a remote event. As long as they can plug in an Ethernet cord and connect to a camera or video mixer, they should be good to go.
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