How to Choose an Encoding Solution

Camera Quality
For those who have analog cameras with no digital outputs, consider using a 3-CCD (or newer CMOS) camera and then use either S-video or component-video outputs to connect the camera to the encoder card’s input. Even with a high-quality camera as the acquisition device, too many content creators settle for the use of composite inputs and substandard cabling in their streaming media projects. The rule of thumb for analog capture is that every 3 decibels of noise (snow, artifacts, etc.) results in a doubling of bitrate to achieve equivalent quality. The converse is also true: Eliminate noise or artifacting in the acquisition device and the bitrate will fall while the compressed content quality remains high.

One Card or Many Cards?
ViewCast "owns" the analog video capture card market, as its ISA cards have given way to PCI-e card sets that handle either single or multiple analog inputs or digital inputs (both HD and SD).

Figure 1. ViewCast’s GoStream SURF is one of the new breed of higher-quality portable streaming audio and video capture stations.

On the analog side, the stalwart Osprey 200 series enables composite- or S-video capture, and a few of the cards allow balanced audio inputs via XLR connectors, while others use RCA or 1/8" (3.5mm) unbalanced audio connectors.

For specialized applications, the Osprey-450e multichannel card enables up to four composite inputs to be simultaneously captured and streamed along with an unbalanced stereo audio pair (RCA via a break-out cable). These cards are aimed at broadcasters who want to send similar signals to multiple locations (we’ll address Simulstream below, which accomplishes a similar task) and those who are looking for digital signage and surveillance streaming opportunities who want to capture multiple discrete video signals.

In addition to FireWire and USB, there are two other digital-camera output flavors that can be connected to a hardware capture card: SDI and HD-SDI. These serial digital inputs, with SDI as standard-definition inputs and HD-SDI as high-definition inputs, enable audio and video to run on a single BNC connector.

The Osprey 500 series card allows composite, S-video, and SD-SDI input and has both analog (XLR) and embedded audio for the SDI connector. If audio is recorded separately, for instance, on an analog soundboard, it can be either directly connected to the analog inputs or embedded into the digital video signal via the use of an audio embedder prior to entering the encoder card on the SDI connector. Likewise, if audio has been embedded on the SDI signal, it can be de-embedded for local playback while still enabling the audio to accompany the SDI signal for streaming purposes.

Following the announcement of its first HD-capable streaming card in 2007, ViewCast updated the card to the 700e. This card recently won a 2008 Streaming Media Readers’ Choice Award in the hardware category, enabling both SD and HD inputs via the SDI connector and supporting up to eight independent embedded stereo audio pairs. The original 700 HD card had a single stereo pair of embedded audio channels, so the firmware upgrade to this card brings significant benefits for audio connectivity.

Since the card can switch back and forth between SD and HD without a noticeable glitch, ViewCast’s HD card has the added benefit of enabling a constant output in terms of size and scale, matching the incoming SD or HD video to a set output parameter.

In the previous section, I noted that Simulstream is another way to send the same content to multiple encoders. This technology acts as a virtual splitter, meaning that a single source signal is input to the capture card and then Simulstream splits the signal into multiple simultaneous streams, sending it to Flash, Real, Windows Media, or other formats/codecs accessible at the operating-system level without the need for multiple encoding cards.

While Simulstream presents a potential single point of failure, the benefits far outweigh the downsides, especially when cards such as the 700e enable discrete configurations of both live streams and on-demand archiving, simultaneously, including cropping, scaling, and logo insertion.