Once you’ve chosen a codec, you have to choose an encoding tool. In this column, I’ll outline the codec-specific and automation-related questions you should ask before using or buying an encoding tool, and then describe the three levels of encoding tools.
Let’s start with Flash. If you’re producing VP6 Flash files, there are two levels of encoding. Specifically, On2’s Flix Pro and Flix Exporter can produce 2-pass variable bit rate (VBR) files. In contrast, all Adobe Flash-encoding tools can only produce 1-pass constant bit rate (CBR). If you’re looking for absolute top quality, you’ll need 2-pass VBR, though for most producers, 1-pass CBR should be fine, and it’s a lot faster to encode.
If you go the 2-pass VBR route, note that there are now two levels of VP6 encoding: VP6-E, for top quality; and VP6-S, for an easier to decode stream. VP6-E should be your default; use VP6-S only when producing for hand-held devices or when rendering at 720p or higher resolutions. In addition, On2 recently announced a codec upgrade that’s supposed to improve quality by as much as 40%. As of June 2008, On2 hadn’t announced a release date, but if you’re buying a new encoding tool ask if it includes the new codec, and if not, when the company plans to add it and how much it will cost. Obviously, you should ask the latter question for any VP6 encoding tools that you’re currently using.
If you’re producing H.264 for either QuickTime or Flash distribution, the most important question is which H.264 codec the encoding tool uses. Most tools (Adobe, Sorenson Squeeze 5, Rhozet Carbon Coder) use the MainConcept codec, which delivers the best quality. Apple’s codec (available in Compressor, ProCoder, and Sorenson Squeeze versions before 5) was the former quality king, but has slipped to last place. In the middle is the Dicas codec, which is available in Telestream’s Episode Pro.
If you’re producing for QuickTime distribution, make sure the encoding tool can "hint" for streaming, which is required for streaming from a QuickTime server. It should also support the Fast Start option for progressive download; otherwise, your file must completely download before it starts playing. There are no Flash-specific encoding parameters required for the Flash Media Server or Flash Player, though I prefer encoders that produce H.264 files with an F4V extension.
If you’re producing Windows Media output, you’ll want an encoder with both VC-1-specific presets and the ability to "tweak" deep encoding settings such as DQuant and B-frame options to produce optimal quality. Currently, the only tool less than $5,000 that offers both is Microsoft’s own Expression Encoder 2. If you’re encoding on a Windows computer, you can adjust the same options by using Microsoft’s command line encoder or the VC-1 PowerToy, though Expression Encoder makes it much easier. If you’re encoding on a Mac, you’re out of luck.
For higher-volume and shared-use applications, you should also understand the potential universe of automation options available in today’s encoders. First is batch encoding, or the ability to queue up and produce multiple files, a basic feature that the Adobe Media Encoder doesn’t currently have. Second is the ability to create "watch folders" that the encoding program watches, automatically encoding any files saved there to the selected set of encoding parameters. Watch folders are a great encoder-sharing feature since any user with access to that particular folder, say over a network, can access the encoder.
Common delivery and notification options include the ability to encode and then FTP a video file to a remote site. Rhozet’s Carbon Coder can "watch" remote FTP locations, retrieve files placed there, encode the retrieved file, and then FTP the results somewhere else, while sending email notifications to interested parties at every step.
Finally, you should also consider the options for accelerating encoding. For example, Apple Compressor lets you share encoding tasks among other computers on a network, as does Sony Vegas, while several higher-end tools offer full-blown server farm capabilities that can mass-produce multiple files faster than real time.
Batch encoding tools at the next level cost between $249 and $1,000. Some are single-format, such as Flix Pro (Flash VP6) and Expression Encoder 2 (WMV); the others are multiformat: Telestream Episode Pro (Mac-only), Sorenson Squeeze (Mac/Windows), and Canopus ProCoder (Windows-only). While these tools offer batch encoding and watch folders, they typically can’t operate over render farms, a limiting factor in very high-volume environments.
For server farm operation, you’ll need to step up to the next level of encoding tool, which includes Rhozet Carbon Coder (Windows) and Telestream Episode Engine (Mac). These solutions start at around $3,000. Other products in this class include Inlet Technologies’ Fathom, Anystream Agility, and Digital Rapids’ line of Stream Software products.
For more information, I surveyed most batch encoding tools, Compressor, and the Adobe Media Encoder for StreamingMedia.com. You can check out my findings in The 2008 Encoder Shootout. I’ve also looked at Carbon Coder and Digital-Rapids StreamZ; both these reviews are available on the StreamingMedia.com website.
Jan Ozer (jan at doceo.com) is the author of Critical Skills for Streaming Producers, a mixed media DVD published by StreamingMedia.com.