How to Choose an Encoding Solution
With all these changes, what are the criteria that should be assessed to make the best purchase for a particular scenario?
This article will provide several options to consider in each of the categories mentioned above, dividing the types of capture, encoding, and transcoding systems into software-only systems, hardware cards, and hardware appliances.
While analog software-encoding systems using analog-to-USB or analog-to-FireWire converters are still available, many software-based encoding systems use built-in USB or FireWire connectors on laptops, desktops, or even mobile devices.
FireWire, also known by the IEEE 1394 or i.Link nomenclatures, is the standard connector on MiniDV cameras for standard-definition (SD) capture and on tape-based HDV cameras for both SD and HD capture. Operating systems from the Mac OS to Windows XP and Vista recognize FireWire cameras, meaning that most any software-encoding system can access the camera at an operating-system level.
With the advent of tapeless HD cameras, such as the AVCHD cameras that use hard-disk or flash memory and a USB connector, the use of FireWire may be replaced by USB 2.0, which is comparable to the original FireWire’s 400Mbps bandwidth. The demise of FireWire for software-only encoding systems may be accelerated by Apple’s decision to eliminate the FireWire port on the newer MacBook (and to use just the 800Mbps FireWire 800 ports on the newer MacBook Pro).
Both of these connectors maintain a direct digital path from the camera to the streaming software. The content on the camera, though, is often encoded at an average of 17Mbps–25Mbps, a much higher bandwidth level than streaming, with AVCHD disk- or flash-based cameras capturing at 17Mbps and FireWire tape-based digital cameras capturing at 25Mbps—almost 10 times the average sustained bandwidth of a consumer’s cable modem or DSL. As such, content coming from these cameras to the streaming server must be either encoded from baseband video (i.e., taking the video back to an analog form for encoding) or transcoded from one digital format to another or at least transrated (i.e., reducing the bandwidth while maintaining the same codec, which is possible in some consumer AVCHD cameras that use an H.264 codec).
For on-demand content, the market for file-based transcoders has a long history. While file-based transcoding options continue to rapidly grow, nearly all software-based file transcoders can trace their lineage to the Terran Interactive Media Cleaner product line, which was purchased by Media 100 and later by Autodesk. From Anystream Agility to Rhozet Carbon Coder to Sorenson Squeeze, file-based transcoders work with watch folders and one or more cores or processors.
Some software-based systems pre-encode content based on particular business rules that may include popularity, bitrate, or other key factors, storing this content in a cache until the business rule fails. As the industry moves forward, the use of file-based transcoders and business rules for caching will move closer to the core, with CDNs providing server-side transcoders and integrated caching as a streamlined service.
In short, software-based transcoding tools are available, but they tend to work best when implemented in a virtualized or software-as-a-service environment.
To properly assess live streaming capture cards, one must consider three areas: the types of inputs, both audio and video, that will be captured; the format/formats and bitrate/bitrates that must be generated for consumption; and content generation—whether all content will generate from a single encoding card, multiple encoding cards, or some form of a hardware/software hybrid. We’ll look at the first and third of these three areas, leaving the bitrate/resolution discussion primarily to other articles in this Sourcebook.
Companies and Suppliers Mentioned