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Producing Conference Video Pt. 4: Live Delivery and Postproduction

What happens when you deliver your event live? This is nothing new for live TV broadcasters, but more and more event video producers are being asked to perform their postproduction activities in real-time—that is, live as the event is occurring.

The postproduction phase of a video project comprises the set of activities a video producer performs after the event is completed. Editing is the main activity but audio and graphics work also fall into the postproduction category, as does DVD authoring, video encoding, and web delivery. But what happens when you deliver your event live? This is nothing new for live TV broadcasters, but more and more event video producers are being asked to perform their postproduction activities in real-time—that is, live as the event is occurring.

These new demands for live video delivery through webcasting (and, to a lesser extent, IMAG) have dramatically changed how an event is captured, directed, mixed, and delivered as the timeline has moved from a delayed turnaround time to as close to real-time as technology and the physical limitations that our world's physics allow. (As with the speeds of sound and light, it still takes a few milliseconds for audio and video signals to be acquired, converted, transmitted, and received.)

In the previous three articles in this four-part series on Producing Conference Video, I discussed the importance of production planning and setup, lighting and audio for video, and shooting presentations and directing live-switched events. Now in this fourth and final instalment I'm going to discuss both traditional postproduction workflows where the event is edited after the filming and live production workflows, specifically as they pertain to live streaming or webcasting.

The New Speed of Video

Postproduction workflows have come a long way since I first started digital video editing with a nonlinear editing computer program in 2001. Analog video tape was replaced by digital video tape, which is, in turn, being replaced by hard drive- and flash memory-based media. Despite these changes, all editors need to ingest their footage before they can start editing, and this used to be the first major bottleneck in the production workflow. As we'll explore, this is no longer the case. Capturing videotape is a linear process, so it takes one hour to capture an hour of footage. Tapeless workflows break away from linear capture times as digital footage can be transferred as fast as the media allows, usually in a fraction of the linear time.

Apples-to-apples comparisons get complicated when comparing new HD video formats to older standards, for the simple reason that most new codecs have a variety of data rate options. Older standards such as DV, DVCAM, DVCPro, and HDV are all 25 Mbps, which is only slightly higher than the 24Mbps of the highest-quality prosumer AVCHD format. But as you move up the codec food chain, codecs come in 35, 40, 50, and even 100Mbps variants. Simple math will tell you that it would take about three times longer to transfer a minute of 100Mbps DVCPro HD footage as it does to transfer a minute of XF Codec footage from Canon's new XF300/305 video cameras, when set to 35Mbps, but this ignores the speed at which the card can theoretically transfer footage, if it even needs to be transferred at all.

On the high end of speed is the new Sony SxS-1 memory card, which promises to have attained transfer speeds of 1.2Gbps. Now be careful not to confuse Gigabits per second (Gbps)with Gigabytes per second (GB/sec), as 1.2Gbps translates into 0.15GB.sec (or 150MB/sec). These transfer rates don't really start to mean much until you translate it into a larger time unit: 1.2 Gbps also equals about 9GB per minute. A bit more math tells me that it takes only 7.1 minutes to transfer a full 64GB (the largest available card capacity), which is a full two hours of footage using the highest quality 50Mbps codec in Sony's XDCAM lineup, or just over 4.7 hours of footage in the SD DV 25Mbps codec. Incredibly, this translates into an unprecedented speed of 1.5 minutes to capture an entire hour of the same DV footage that it used to take an entire hour to capture (and when you factor in the tape rewind time the SxS-1 footage would likely be ready to edit before the tape's footage was even ready to begin capturing).

So what's better than fast transfer times? No transfer times at all. Most of the flash memory formats can be edited straight from the card, without even being transferred to the computer's hard drive. Whether or not this is practical or not depends on the speed of the card and its corresponding ability to serve up the video files fast enough for smooth preview and editing.

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