Encoding
For rare, live webcasts, HOB encodes and streams directly to the Internet. For delayed webcasts, HOB prefers to encode live or taped video live-to-file, even though it's less ideal than capturing to an .avi or .mov file before encoding. (A higher-quality encode can be achieved by first digitizing the video as an .avi or .mov file, then later rendering out to the streaming files over a longer period of time. HOB only uses this method for demos and other short content.)
For basic, non-pay-per-view webcasts — either live-live or simulated-live — the video line-cut and the stereo audio mix feed a bank of six rack-mounted encoders delivering 28.8Kbps, 56Kbps, and 100Kbps streams in both Real and Windows Media formats. (Apple's Quicktime is not currently supported. Fracassi says, "If Steve Jobs were to call me today and say, 'Here's the funding and resources to put your thousands of hours of programming into Quicktime,' I would do it in a heartbeat. We don't want to leave anybody out. But you've got to direct your programming at what the market is demanding, and right now the market is not demanding Quicktime.") For broadband pay-per-view events, additional encoders are brought in to pump out 300Kbps and 650Kbps streams.
Because the HOB encoders currently use Osprey 100 analog video capture cards, the digital video line-cut from the switcher must be converted to analog (through an Aja D-to-A converter) before encoding. HOB is currently testing the new Osprey 500 digital video capture card and hopes to avoid any D-to-A conversion in the future. The encoders use SoundBlaster Live audio cards from Creative Labs.
HOB uses discreet encoders for each bit rate in each format it streams. Wild says, "It is technically feasible to encode multiple bit rates on a single box, [but we] want 100 percent of the CPU cycles going to make one stream look good." San Jose-based Telenet Systems built the encoders to HOB's specs, using a 600MHz Pentium III processor and 256K of RAM for each box. CPU-hungry 300Kbps or 650Kbps streams use encoders with dual 600MHz processors. Wild notes, "The encoders themselves are the cleanest configuration of computer you could imagine. No frills. We install a bare-bones operating system and the encoders, and then leave it alone. You don't want other software interfering [with the encoding]." HOB does use hot standby encoders, but Wild observes, "I can count on one hand the number of times I've seen an encoder fail."
Because the aspect ratio of the video window is not limited to the 4:3 seen in NTSC television, HOB can encode in native 16:9 without "letterboxing." The 300Kbps and 650Kbps streams are encoded for a 368x208 video window at 30fps; 100Kbps streams are 272x152 at 15fps; 56Kbps streams are 212x116 at 10fps; and 28.8Kbps streams are 184x104 at 10fps. The audio codecs for the 300Kbps and 650Kbps streams use a 64Kbps bit rate and 44KHz sampling rate (stereo); 100Kbps streams use a 32Kbps bit rate and 32MHz sampling rate (stereo); 56Kbps streams use a 16Kbps bit rate and 22KHz sampling rate (mono); and 28.8Kbps streams use an 11Kbps bit rate and 11KHz sampling rate (mono). For non-live-live encoding, de-interlacing and other optimization is accomplished using Media Cleaner Pro.
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