How to Choose an Encoding Solution

How about HDMI and DVI outputs? While they provide bidirectional digital video/graphics outputs—and in HDMI’s case, multiple digital audio outputs—most laptops or desktops are designed only to output HDMI or DVI and will not allow input on their built-in connectors.

Blackmagic Design, traditionally a nonlinear editing hardware capture card company, offers an HDMI capture card that’s designed to connect to consumer and prosumer cameras. The Blackmagic Intensity card enables HDMI capture from AVCHD disk- or flash-based cameras, providing the benefit of bypassing any potential encoding issues when moving from AVCHD to other formats, as the HDMI signal is grabbed directly from the camera’s CCD or CMOS chip prior to encoding.

Hardware Appliances
As encoding and transcoding continue to grow in popularity, the move toward appliance-based systems also gains momentum. In essence, an appliance is a single-purpose computer consisting of the software and the hardware needed to perform real-time encoding or transcoding. These appliances are split into two types: rack-mounted and portable systems.

Portable Encoder Appliances
For as long as there have been encoding systems, there has been a desire to take encoding into the field in as compact a format as possible. This, perhaps, explains the rise of software-based encoding systems, which required nothing more than a laptop to both encode and serve streams. These were followed by synchronized presentation systems, such as Accordent and Mediasite, which required hardware to capture both the video and audio stream in addition to the synchronized VGA capture of webpages or PowerPoint slide decks.

Lately, though, the focus has shifted to higher-quality portable streaming audio and video capture stations, some with integrated "confidence" monitors that eliminate the need to carry a separate monitor to verify the capture and stream. Examples of these include the Digital Rapids TouchStream and the ViewCast GoStream SURF, the latter of which does require a separate monitor. Both offer on-location live streaming of events such as concerts, sporting events, remote news (electronic news gathering), depositions, courtroom proceedings, corporate training, and other critical live-encoding scenarios.

Figure 2. The TouchStream offers AVC, H.264, and MPEG-4 Part 10 for Flash and QuickTime; VC-1 for Windows Media; On2 VP6 for Adobe Flash 8; 3GPP for mobile devices; and even MPEG-2.

With portable systems, as with most of the rack-mounted hardware appliances noted below, a significant number of formats can be offered for live streaming. The TouchStream, for instance, offers AVC, H.264, and MPEG-4 Part 10 for Flash and QuickTime; VC-1 for Windows Media; On2 VP6 for Adobe Flash 8; 3GPP for mobile devices; and even MPEG-2.

Software-based systems can usually use many of these codecs as well, but often a software system is either optimized for a single codec (think Windows Media Encoder or Flash Media Encoder) for real-time encoding or optimized multiple encodes. Portable systems are also primarily based on CPU processing as they are, at their core, portable computers complete with USB connectors.

Rack-Mounted Encoder Appliances
Besides ViewCast’s Niagara series and Digital Rapids’ StreamZ rack-mounted encoding appliances, there are several other companies in this space: Envivio; HaiVision; Inlet Technologies, which was started by some of the original creators of the Osprey cards that ViewCast now owns; Media Excel, which was started by MPEG-4 committee member Jongil Kim and several other key Ph.D.s in image processing; and Streamtel, an Italian company focused on H.264 delivery for the broadcast market.

Figure 3. Inlet’s Spinnaker is an example of a rack-mounted encoding appliance.

The primary difference between Inlet, Digital Rapids, and Media Excel is their use of different hardware architectures, ranging from general-purpose x86-based CPUs to DSPs. Media Excel has focused on DSP-based solutions, which are a precursor to ASIC-based transcoders. The other companies’ systems use general-purpose CPUs; and the Digital Rapids, Inlet, and ViewCast systems also double as Windows XP-standard machines in a pinch—as does the NewTek TriCaster series of encoder/switchers—but this practice should be limited as the machines are optimized to encode and the addition of extra programs or plug-ins could limit future appliance-encoding throughput.

Many of these companies are also pursuing the transcoder appliance market as well. Media Excel claims that the use of DSPs for transcoding enables greater flexibility, higher file throughput, and a lower total cost of ownership.