Movie Making Manual/Digital Video/Analog vs. Digital


Digital Video Production Manual

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Analog vs. Digital


Digital information recording is an evolution from analog which is most heavily influenced by computers and their popularity and accessibility. Originally video production had a large gambit of machines and electronics specifically created for that industry. As computers became more advanced, cheaper, and more accessible applications for the computer spread to almost every industry. The widespread application of computers for manipulation of video was hampered because video requires relatively massive storage, processing, and data transfer requirements. As hardware has become cheaper and more powerful, and storage space in particular has become plentiful, using a computer to manipulate video has become more economically viable than not. Currently video production is towards the end of a transition in technology from an analog based system to a digital based system.



Why use digital?


Digital has advantages and disadvantages like any tool, but the general consensus is that digital is better, and for good reason. In post-production of analog video, there are basically two editing options. There is assemble (aka linear) editing, in which the final product is assembled from the various pieces in order from the beginning to end. If a change needs to be made at any point, then everything from that point to the end of the change must be recreated from the original source material. This, of course, is problematic if the needs of the production are the least bit dynamic. Avid was the first popular computer based “nonlinear” editing application, originally created for film editing. It was a small step toward moving into professional video editing applications. Non-linear editing allows the editor to “ripple” an insert so that everything that comes after the change is shifted to accommodate the shift. As computer-based editing became more popular, the choices were either staying with the hardware controlled tape-to-tape linear systems or digitizing the analog footage into a computer for digital editing. Since computers are digital systems--not analog--the video signal is translated into a digital signal. The evolutionary step was a short one to have the video signal recorded in a digital format.



Limitations of Analog


When using an analog system, there are some major inherent limitations that can be problematic. The first is when you’re editing video the process doesn’t take the physical tape material, slice it with a razor, and combine it with other clips as one would with film. Rather a VTP would read the information from the source tape and send the signal to a VTR, which would record the signal onto a new tape. This is called a "generation" and analog has a tendency of not making a 100% exact copy during this process. As video is pushed through more and more generations, the signal degrades until it is essentially unrecognizable. There are tools that help reduce this--like waveform monitors, signal amplifiers, etc.--but most analog video is unusable after 5 to 10 generations (for professional standards). On the other hand, as long as the information isn’t reprocessed (such as in color correction, transitions, etc.) DV can withstand dozens of generations and some manufacturers have reported over 100 generations with no perceptible loss in picture quality. **citation needed** On the other hand, there are limitations to a digital system mainly in regards to sample rates and aliasing. However as the delivery of the video signal is not analog anyway (pixels) digital information processing on these discrete units seems to make the most sense.

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