Figure 3.5

An analog sound wave (top) is broken into small samples, resulting in a digital audio file (bottom).

Working with Analog or SD Video

It’s hard to believe that analog and SD video were a common part of the filmmaking process until as recently as five years ago. Technology has improved so quickly that it’s now pretty easy to move forward with HD and never look back.

Unfortunately, not everyone has this luxury. If you work on a TV show that’s been around for a while, you’ll have to deal with SD clips from old seasons from time to time, or perhaps you’re doing a documentary on Martin Luther King, so all your archival media is in SD format. That means you’re going to have a project that mixes both HD and SD media. Or maybe you invested in high-quality SD equipment and aren’t quite ready to make the leap to HD. Whatever the reason, there are some things to be aware of when dealing with analog/SD footage:

nThe aspect ratio of analog/SD footage is 4:3 (or 1.33:1).

nThe resolution of analog video is 640 480 pixels and each pixel has a rectangular shape. Most forms of digital video have square pixels. This is why analog video sometimes looks stretched on your HDTV.

nThe resolution of SD video is 720 480. This digital format is much more easily compatible with HD formats.

44 The Digital Filmmaking Handbook, 4E

nThe frame rate of analog video (in the United States) is 29.97fps.

nAnalog video is interlaced, which means it has two fields for every frame.

nIf you transfer analog video to an HD format, you will have to decide whether or not to have it blown up to fill the width of the entire frame, which will mean that you must crop off the top and bottom of the image, or to have it fill the height of the frame, which means there will be two black areas on either side of the frame (see Figure 3.6). Some people choose to fill these areas with graphics or a background of some sort. (More about integrating HD and SD footage in Chapter 17, “Titles and Effects.”)

For those of you who must continue to work with analog footage, we’ve saved the discussion of how analog video works from the previous edition and put it on the Web site for this book at www.thedigitalfilmmakinghandbook.com.

Figure 3.6

When transferring analog or SD video to HD, you must choose between a cropped image (bottom) or an image that does not fit the entire frame (top).

Why 29.97?

When broadcast video in America was first standardized, all television was black and white (or more correctly, monochrome) and had a frame rate of 30fps. When color technology was added, broadcasters and the FCC needed to figure out a way to differentiate color video from black and white. The solution? Slow the frame rate of color video down by 1/1000th of a percent (.001). That way, existing monochrome TV sets could continue to pick up the monochrome 30fps signal and new color TV sets could pick up the 29.97fps color signal. Unfortunately, in America we are now stuck with the legacy of obsolete monochrome media and have all sorts of strange frame rates that are a bit difficult to remember. When transferring 24fps media to NTSC video, the 24fps footage is also slowed down .1% to 23.976fps in order to maintain audio sync with 29.97fps media.

WHAT TO WATCH

Paranormal Activity is a great example of how any type of image-quality can work if it suits the story. This movie feels so real precisely because it was shot with the kind of camcorder almost everybody owns.

Stick with the New

Using older video gear can introduce a world of pain to your project. Older, analog, or SD video is very different, technically speaking, from HD video. They have different frame rates, different aspect ratios, different pixel shapes and most importantly, don’t look as good. Trust us, it’s not worth it!

Timecode

When you shoot digital video, your camera keeps track of the time and assigns a number

to every single frame that you record. This is extremely useful in postproduction if you have to move your media from one system to another, if you are working with low-res proxies and plan to upgrade your media later on, or if you need to reconstruct your project at a later date. It can also make synchronizing multi-cam footage much easier.

Some cameras automatically use their internal clock to record timecode that corresponds to the actual time of day, known as time-of-day timecode. A shot that has a starting timecode of 11:07:40:15 was shot at about seven minutes after 11 A.M.

SMTPE timecode is a standardized type of timecode that doesn’t reflect the time of day. Rather, the user can set the starting time however they want. Typically, the first tape or disk is set to 01:00:00:00 and then next one is set to hour 2 and so on.

Because the frame rate of analog NTSC video is an odd 29.97 frames per second, drop frame timecode was developed to help round off the fractional frames to less awkward whole numbers. Drop frame timecode is the standard for analog and digital 29.97fps video for broadcast television in America.