CHAPTER

9   Recording

Introduction

Recording good-quality sound and images is extremely important, as poor-quality recordings can destroy the impact of what could otherwise be a high-quality production. Understanding how audio video and film recording devices work will help ensure that you consistently record good-quality sounds and images. Acquiring a basic understanding of media technology increases your ability to control aesthetic variables, whether they are realist, modernist, or postmodernist. If you understand the means by which images and sound are recorded, you can consistently obtain high-quality recordings of the intended production. Visual and aural media are based on digital and analog electronic, magnetic, and photochemical recording processes. This chapter introduces you to audio and video electronics, as well as film photochemistry.

ANALOG AUDIO

Analog recording produces a continuously varying magnetic optical copy of the electrical fluctuations stimulated by the original sound waves. The original sine wave variations of the audio signal are duplicated in sine wave variations, matching as closely as possible the original signal. Magnetic media passes over a magnetic sound-recording head, consisting of a magnet with a coil wrapped around it, which carries the electrical sound signal. As the voltage in the electric sound signal fluctuates, the magnetic field through which the medium is passed changes, recording the sound on the tape. A bias signal (30,000 Hz or above, which is outside the range of human hearing) produced by a bias head aligns the signal to record on the linear portion of the magnetization curve. In the playback mode, the medium is passed over a playback head (in some decks the same head is used for both recording and playback), which picks up the prerecorded tape’s magnetic variations and causes a weak electrical current passing through the magnetic head to fluctuate accordingly This signal is then amplified; that is, it is increased in strength and intensity so that it can be sent to a loudspeaker, headphones, or another recorder.

Audiotape Formats

Audiotape for either analog or digital recording is made up of particles of iron oxide or other metallic substances attached to a flexible support base. Tape formats can be categorized on the basis of two factors: the dimensions of the tape and the form in which it is packaged. Tape dimensions differ in terms of thickness and width. Audio quality generally increases with increasing tape thickness and head width and with the relative speed of the head to tape. The thickness of audiotape is measured in mils (thousandths of an inch). Tape thicknesses vary from 1½, to ¼ mil. Audiotape also comes in a variety of widths, from ⅛ inch, to two inch. Multitrack analog and digital tape recorders (each track is a separate tape path) require wider audiotape. As many as 64 separate tracks can be recorded on some multitrack machines using two-inch-wide audiotape (see Figure 9.2, presented later).

Audio signals in video recording are usually recorded directly on videotape in a variety of formats, which are discussed later in this chapter. Film audio may be recorded on a separate ¼-inch audiotape, onto full-coat film stock, on a portable digital recorder, or directly onto the film itself. In the latter case, the edge of Super- 8 mm or 16 mm film is coated with magnetic material; this is called magnetically striped film (Figure 9.1).

FIGURE 9.1 Magnetic film tracks are laid down on the edge of the film if a picture also is recorded on the same stock. If the film is to be used for sound only, the track can be laid down in one or more paths down the middle of film as magnetic full-coat film.

Analog Audio Recorders

The enclosures in which tape is packaged and the type of machines on which the recordings are made provide another means of differentiating recording formats. Analog tape can be obtained in the form of cartridges and cassettes, as well as in open reels. Cartridges consist of continuous loops of 1½-mil, ¼-inch audiotape, ranging from a few feet to several hundred feet in length and from a few seconds to several minutes in duration. Cassettes are pairs of small reels encased in a plastic housing. The standard width of cassette tape is ⅛ inch, and the normal cassette tape recorder speed is relatively slow: 1⅞ inches per second. Open reel tape has the advantage that it can be edited (see , Editing), runs at higher speeds, and is available in a variety of tape sizes. Cartridges are quicker and easier to set up and recue—that is, to find the specified starting point (Figure 9.2).

FIGURE 9.2 The arrangement of audio tracks varies with the type of tape deck and the number of audio tracks, sync, pulse, or timecode tracks that need to be recorded.

Audiotape Speeds

The speed at which an audiotape is driven directly affects the amount of tape that is used and, more important, the quality of the tape recording. In general, faster recording speeds produce better-quality recordings. Analog tape recorders have a speed-control setting that can be adjusted to any of the following speeds: 15/16, 1⅞, 3¾, 7½, 15, or 30 inches per second (ips). Professional recordings of live music, if recorded on analog equipment, are usually made at tape speeds of 15 ips or above. Most multitrack sound analog recording is done at a speed of 30 ips. Simple voice recordings are frequently made at 7½ ips or even 3¾ ips.

DIGITAL AUDIO

A digital audio recorder samples or evaluates the electrical sound wave thousands of times every second and gives an exact numerical value to the electrical sound signal for each specific instant of time. The numerical values are coded into a series of on-and-off electrical pulses, known as binary code. These are the same types of signals used by computer systems. These electrical pulses are not an electrical copy or analog of the sound wave. The only signal that is recorded is electricity that is either entirely on or entirely off, rather than different gradations of electrical current, as is the case in analog recording. Despite the increase in digital audio recording, the highest quality original sound recording is on an analog system that avoids the loss of conversion through compression and sampling and quantization (Figure 9.3).

FIGURE 9.3 The common analog audiotape decks are ¼-inch reel-to-reel, broadcast cartridge, and a standard ⅛-inch cassette deck.

The values of the recorded digital signal are determined by two factors: sampling and quantization. The analog signal is analyzed by periodically sampling its frequency. The more often the signal is sampled, the higher the quality of the digital signal. The rate must be at least twice the highest frequency to be reproduced. Today the standard sampling rates are 32 kHz, 44.1 kHz, and 48 kHz. To determine dynamic or loudness range, assigned binary bits determine how many different discrete audio levels can be recorded. Standards vary from a low of 8 bits to a high of 128 bits. In both sampling and quantization, the higher the rates, the better the quality; but at the same time, the cost and amount of memory required increase (Figure 9.4).

FIGURE 9.4 An analog signal is a continuous signal equivalent to the frequency and level of the comparable audio signal. On the other hand, a digital signal is a series of pulses that “samples” the original sound at frequent intervals and then converts those samples to on-and-off digital signals that can be converted back to the original sound.

Digital recording extends the recordable range of intensities and frequencies and virtually eliminates many other problems inherent in analog recording, such as tape noise, cross-talk (two recorded tracks on the same tape interfering with each other), and print-through (one layer of recorded tape bleeding through and interfering with another). Flutter (an unwanted fluctuation in pitch) is another common analog recording problem. Digital recordings can be duplicated without degradation of the signal and can produce a much more permanent record than analog recording. Fine gradations of analog signals can completely fade away and be lost forever, whereas a magnetic signal that is completely on or off can easily be restored to its original state as the ons begin to fade. For these reasons, digital recording has replaced analog recording as the professional audio standard.

Digital Recorders

Today there are four types of digital audio recording media: digital audiotape (DAT), audio-DVDs, CDs, and tapeless systems. DAT recorders operate in two different methods: stationary head (S-DAT), also called DASH, and revolving head (R-DAT) (Figures 9.5 and 9.6).

FIGURE 9.5 Digital tape decks operate in either R-DAT, or S-DAT, or DCC format. Digital decks, like analog, can record several tracks simultaneously in any of the formats. (Courtesy of Nagra.)

FIGURE 9.6 Audio may be recorded without using tape by recording directly onto computer floppy disks, a hard drive, or flash memory to be converted to another format. Audio can also be recorded directly or as a final format on CD discs. (Courtesy of Studer.)

The design and operation of the stationary-head DAT recorders are much like analog decks in that a tape is drawn across a head or series of heads, depending on the number of tracks to be recorded at a set speed. A ¼-inch S-DAT recorder can record up to eight tracks plus sync tracks, and a one-inch deck can handle up to 32 tracks. DAT recorders used a type of preemphasis added to the recorded signal to recreate the “bass” values of analog recordings, but they do not need pre- and postbias adjustments to compensate for tape analog tape hiss. There are three different S-DAT compatible recording systems; all use metal-particle tape.

The R-DAT machines borrow from helical videotape technology by mounting the record heads in a revolving drum and wrapping the tape part way around the drum.

The heads in the drum rotate in the opposite direction of the tape movement and, as in VCR technology, this movement increases the tape-to-head relative speed, thereby increasing the quality of the recording. There are several noncompatible S-DAT standards, but most R-DAT recorders are compatible, and because they can be manufactured in relatively small packages, they make ideal field recorders for video, film, and concert recording.

DAT was designed as a professional recording medium, and the two forms have found their niches in the recording industry. R-DAT also has become a backup tape format for nonlinear computer editors. If used for video recording, the signal is compressed, creating a recording that matches the quality of DV, now the most common low-cast video recording format.

With the rapid increase in computer memory and the lowering of costs, tapeless audio recording has developed and finds a place in the industry. Audio is simply fed into a computer and the digitized signal is recorded on one of several recording media: one or more computer hard drives, solid-state random access memory (RAM), flash drives, or some form of optical disc. The most common form of the latter is a write-once-read-many (WORM) drive, which has a high memory capacity, or a recordable compact disc (CDR), or audio-DVD. With the advent of the Motion Picture Experts Group-Layer 3 (MP3) standard, audio may be downloaded from the Internet onto one of several digital music recorder/players. Each requires a digital signal input from either the Internet or any other digital source, such as a CD. Most of the small portable players play back from either disks or miniature memory chips for up to two hours at a time. It is clear that the question of copyright infringement using such technologies has become a major legal issue. Misuse of MP3 can bring heavy fines, prison penalties, and loss of the use of the Internet. The “free” use of downloading music from the Internet has been replaced with systems charging small fees for each download, a fair and equitable resolution of the problem.

It is possible today to feed a signal directly from a microphone into a computer, add any number of tracks, manipulate the signals in any manner desired, and output the finished signal to a digital format for distribution or playback without ever leaving the digital domain. Once the audio has been digitized, it may be edited as if the audio were a series of symbols in a word processor. The audio can be cut, rearranged, equalized, and mixed in any combination, depending on the complexity of the computer program. Once entered into the computer, the editing process is much more efficient than any other form of audio editing, but all of the audio must be entered into the computer in real time, which may be time consuming if there is much original material.

Digital audio processes have nearly replaced analog processes, but just as magnetic recording replaced electronic disc recording, and electronic disc recording replaced acoustical recording (although the majority of audio recording and processing are now through digital means), some analog audio recording will always be needed.

ANALOG VIDEO

Composite Video Signal

Video cameras transform and transmit visual images by converting light energy into electrical energy. The composite video signal of a visual image can be transmitted along an electrical conduit or wire in a closed-circuit system to a video monitor or a video recorder. The composite (or complete) video signal must be made up of three major components to be accurately recorded. The three components are the video signal, synchronization pulses (sync), and control track (CT) pulses.

Video Signal

The portion of the composite video signal that actually carries the voltages that are transformed into picture elements in a monitor and are recorded is called the video signal. That signal varies in voltage in direct proportion to the intensity of the light striking the camera sensor. In the component system, the video signal is a combination of all three basic pulses. In a composite color system, the video is more complex because there are three separate color signals combined out of phase, plus the basic component pulses. The advantage of the composite system is that it allows for better control of the color factors and avoids some of the color artifacts inherent in the component system, although composite requires more circuits. As in analog video systems, digital systems must maintain accurate and precise recording levels as well as specific digital and phase relationships between signals.

Synchronization Signal

For a video recorder or monitor to use the electronic signal transmitted from a camera, it must have some reference for the scan and the field rates of the picture. A synchronizing or sync signal, which functions like electronic sprocket holes, is fed either to the camera or generated internally in the camera during recording.

The sync signal is necessary for stable reproduction of the original signal. There are actually two sync signals: horizontal sync and vertical sync. The horizontal sync signal controls horizontal scanning and blanking, whereas the vertical sync signal controls the rate of the vertical scanning and blanking. These sync signals are passed along within the composite video signal so that all recipients of the whole signal will reproduce the picture at the same rate and direction as the camera originating the signal.

Control Track Pulse

A video recorder records a pulse signal, called a control track (CT) signal, that guides the playback video heads into position to accurately follow or track the signal laid down by the record head at the time of recording. A servo capstan—that is, a rotating tape drive cylinder with an accurate motor—varies the speed of the playback so that proper synchronization is maintained. It also moves the videotape through the recorder at the correct speed and ensures that it is aligned properly by the CT (Figure 9.7).

FIGURE 9.7 Helical videotape tracks follow a general pattern of several linear audio tracks, a linear control track, a linear timecode track, and video recorded at a steep angle in slashes across the tape by a video head rotating at a high speed in the opposite direction of tape travel. This method of recording video is necessary for the high head-to-tape speed required to record the high frequencies of video.

Monochrome and Color Video

A black-and-white system transmits only the brightness values of light, also called luminance, not hue or saturation. There are several different camera pickup systems for creating color video images. Some use only one sensor, and others use two or three. Light entering a video camera is divided into its red, green, and blue components by using color filters. The three-color information picked up by chips is then encoded as two chrominance or color signals, which are called the I and Q signals, and one luminance or brightness signal, which is called the Y signal. The signals are then digitized, as light striking each sensor creates an analog variation in voltages.

This chrominance and luminance information is then transmitted to the recording medium, where it is recorded. Light, as explained in Chapter 7, Lighting and Design, can be analyzed and manipulated on the basis of its three characteristics: hue, saturation, and brightness. Different wavelengths of light are perceived as different colors, or color hues, such as red, green, and blue. Color video and film systems are capable of recording and projecting a wide range of color hues. Like our eyes, these systems depend on three basic hues: red, green, and blue, called the additive color system. Light can be described in terms of its color saturation and brightness as well as its hue. The saturation of a specific hue indicates its color purity, that is, the amount of grayness the color contains. A vibrant but pure color of red, such as on a stop sign, is heavily saturated. In video, saturation is translated into a chroma or chrominance signal. Brightness refers to a light’s intensity, its lightness or darkness. Bright lights have strong intensities.

In video, brightness is reproduced in the luminance signal. Black-and-white video and film recording devices are only sensitive to the brightness or luminance of a light, not its hue or saturation. Two distinctly different colors may contrast with each other to the naked eye, but if they are equal in brightness, a black-and-white recording depicts them as virtually identical. When recording in black and white, hue and saturation can generally be ignored, because brightness values are paramount. Hue, saturation, and brightness play key roles in video and film color recording processes. The basic principles of colored light, covered in Chapter 7, Lighting and Design, provide the basis for the recording processes of both video and film. Both the National Television Standards Committee (NTSC) and the Advanced Television Systems Committee (ATSC), the technical group formed to set the standards for digital and high-definition television, video signal reproduces color by keeping the three signals (I, Q, and Y) separate, either by combining them in one signal with each of the components out of phase with each other (the composite system) or by actually using three circuits to keep the signals separate (the component system).

Scanning Systems

Before discussing the method of recording a video signal, it is important to understand the scanning systems. There are two basic scanning systems: interlace and progressive. The United States and other countries that use NTSC standards for analog television use an interlace system of scanning to create and to reproduce the picture. Each picture is scanned twice: first the even lines are scanned, constituting one field, and then the odd lines are scanned, making up the second field. The two fields together make up a complete picture that is scanned every 1/30th of a second. Interlace is an efficient system, but it can introduce artifacts or distortions in the picture. Computer systems use a progressive system of scanning. Each frame is created by scanning every line in order to make a complete frame.

Improved modern technology has made progressive scanning a preferred system. Progressive systems can scan at the rate of 24, 25, or 30 frames a second. The recording process depends partly on the frame rate of the system in use, because the recording and editing systems must match the scan rate and the scan system used. As analog and standard definition (SD) systems are being replaced by high-definition (HD) systems, the number of lines and aspect ratios also are changing. The Federal Communications Commission (FCC) has ruled that 16:9 is the accepted wide-screen standard, and the number of lines may be either 525 or 625 for analog systems and 480, 720, or 1,080 active lines for digital systems. The end result is that there are 18 different combinations of aspect ratio, line rates, and progressive or interlace scan system standards set by the Advanced TV Systems Committee (ATSC) for advanced TV [ATV]—digital and high-definition—systems.

Helical Scan Recording

All videotape recorders, either analog or digital, now use the helical scan method of recording. Helical scan recorders use two or more video heads, which continuously record electrical video signals. As magnetic tape travels from left to right across the recording heads, the heads rotate in a clockwise direction, opposite to the movement of the tape. On a two-head recorder, each time a single head passes over the tape, it records a complete field of 262 half-lines of video in a 525-line system or 540 lines in a 1,080 system. At the exact instant that the first rotating head disengages from the tape, the second head engages it, so that a continuous recording of the television signal is made along the tape by consecutive heads. The passage from one head to the next corresponds to the vertical blanking period and is a crucial part of maintaining synchronization. The vertical blanking period is the time when the scan line is dropped to black and cannot be seen as it retraces to start a new scan line. The combined passage of the two heads records a complete frame of 525 or 740 lines (Figures 9.8 and 9.9). In a progressive scan system, two or four heads alternate, each creating a single frame as they pass over the tape. Instead of alternating scan lines, as in the interlace system, the progressive system scans lines continuously from the top of the frame to the bottom to create a single frame.

FIGURE 9.8 The video head of a helical recorder contains from two to eight different recording or erasing heads depending on the complexity of the format.

FIGURE 9.9 Each of the helical videotape formats records its signals in different paths, at different angles, and at different speeds. Each format historically was developed to provide a higher quality at lower cost. As time passes, the newer digital formats will replace the present analog formats.

The videotape is wrapped around a semicircular drum, and the heads maintain continuous contact with a semicircular wrap of tape around the drum, moving in a downward diagonal direction as they rotate past the tape. Because the recording is made in a slanting movement of the head across the tape, a helical scan recorder is sometimes called a slant-track recorder. The linear speed of the tape passing the rotating heads in a digital recorder varies from 100 mm/second (approximately 250 ips) to 200 mm/second (approximately 500 ips). Although the speed of initial recording cannot be varied, a helical scan recorder can be slowed down or speeded up in playback to create slow- or fast-motion action. During slow motion, scan lines are repeated, but during fast motion, some lines are skipped. The image can also be stopped and the action frozen by repeating one recording line or complete field of the video image, called a freeze frame, which is often designated as the pause mode during playback. High-quality ½-inch helical scan recorders and digital recorders allow for special effects creation without sacrificing image quality.

Videotape Formats

Videotape contains iron oxide or other metallic particles that store electrical information in magnetic form. These microscopic particles are attached to a flexible support base, such as cellulose acetate or polyester (Mylar) (Figure 9.10). Videotape recorders (VTR) or videocassette recorders (VCR) are capable of both recording and playing back video information on reels or cassettes of videotape. The signals may be either analog or digitized video or audio signals.

FIGURE 9.10 Audio and video recording stock is manufactured in a great variety of widths, thicknesses, and magnetic coatings depending on the purpose for which the tape is intended. The recording media today moves from magnetic tape to disc and on to solid-state media. From top down on the left: Mini-VHS, DVCPRo, Hi8, M-II, BetaMax, BetaSP, Quarter-cam, U-matic, DV. On the right: two-inch quad cart, two-inch quad open reel, EIAJ ½-inch, Type “C” one-inch. In front of the reels, a DVD and ½-inch floppy.

The actual recording of video and audio signals is done by video and audio record heads, which also function as playback heads. The audio and video heads are usually separated from one another because the recording of a video signal requires a complex movement of the head with respect to the videotape, whereas an audio head remains stationary. Some tape decks record audio signals using rotating audio heads parallel to the video heads or record digital audio embedded within the digital video signal (called pulse-code modulation [PCM]). An erase head erases information previously stored on the videotape before recording new images.

D-9 (a component videotape format) uses separate heads for recording and playing back so instantaneous monitoring and even in-camera effects can be created using both heads. The format, or width, of videotape ranges from 8 mm to 19 mm. Helical scan recorders use one of the following formats: 6.35 mm (¼-inch), 8 mm (⅓-inch), 12.5 mm (½-inch), or 19 mm (¾-inch) videotape. Small-format helical scan recorders use 6.35 mm (¼-inch) or 8 mm (½-inch) videotape. Digital recorders use tape from 6 mm to 19 mm wide. A variety of different helical scan systems have been developed for recording analog signals on ½-inch videocassettes: VHS, S-VHS, and Betacam SP; for digital recordings, digital Betacam, Betacam SX, D-3, D-5, and D-9. These systems all use ½-inch videotape in closed cassettes and helical- or slant-tracking techniques, but the actual scanning of the videotape is sufficiently different so that they are noncompatible systems. As an example, a D-9 recording, which uses a slightly larger videocassette and a different loading mechanism, cannot be played on a Betacam SX machine and vice versa. As of this writing, four tape formats specifically designed for high-definition are available: D5-HD, based on D-5; D7-HD, based on DVCPro; D9-HD, based on Digital-S; and HDCAM and XDCAM-EX based on Betacam. Some other digital formats are available with upgrades or modifications that allow playing or recording an HD signal. Each season, new forms of digital and HD equipment are designed and produced, making it difficult to keep up with the latest available equipment. At the same time, many of the present formats may not find a market and may disappear within a year or two of their first appearance.

The digital systems are all high-quality recording systems, but they are also incompatible with each other (except for D-3 and D-5; and Beta, Betacam SP, and Digital Beta SX) or with any other ½-inch system. Some consumer ½-inch videocassette recorders are capable of running at a variety of speeds, so anywhere from one to six hours of recording can be made on the same videocassette. Some videocassette recorders are capable of recording and playing back several different types of television signals, such as NTSC, PAL, SECAM, and various ATSC using different types of electrical current. When large quantities of video or audio material needs to be recorded and accessed in a nonlinear manner, computers with maximum digital storage capacities are used. These systems are called servers (Figure 9.11).

FIGURE 9.11 A video server that is designed to record and play back digital video/audio cuts on a nonlinear basis. It emulates videotape recorders, cart machines, and video storage systems. (Courtesy of Philips Broadcast Television Systems Company.)

High-quality ½-inch analog and digital tapes used for professional recordings allow sufficient space for a control track, up to four soundtracks, a timecode track, and one video track. One-inch, once the professional broadcast standard, has been replaced by digital and ½-inch tape formats, solid-state, direct to disc, and hard drive media. Smaller analog consumer format videotapes can be broadcast when they have been channeled through an image stabilizer, known as a digital time-base corrector, or TBC. A TBC accurately synchronizes the scanning process by changing a conventional analog signal into a more easily controlled digital signal, thus providing high-quality video sync signals (see , Editing). Minor variations in synchronization that cause a picture to jitter are eliminated using a TBC, which makes it possible for smaller format recordings to be broadcast directly or dubbed up to better quality videotape formats.

Videotape Sound Synchronization

Synchronization between sounds and images is simple to maintain in videotape recording. A single videotape recording machine may be used to record picture and sound elements simultaneously on the same tape. In most videotape recording, onset or synchronous sounds are recorded on the track located away from the edge of the tape. There is a slight distance separating the points at which the sounds and the picture are recorded on the videotape, because on most types of videotape recorders the video record and playback heads rotate but sound heads remain stationary. During electronic editing, then, the corresponding sound and images must be picked up from slightly different points on the tape. However, because videotape is always played back on a machine that has the same gap between images and sounds, this distance creates no real problem in terms of synchronizing sounds and images. Control track recording (discussed in , Editing) is an important reference for postproduction editing, although some machines provide another type of reference, called SMPTE timecode, which is discussed in , Editing.

DIGITAL VIDEO

Digital video technology is the same as digital audio, except that much higher frequencies and a greater quantity of recorded material must be handled. The original analog video signal is sampled and quantized, requiring up to 300 MB per second of recorded program, as compared with less than 100 K per second for digital audio. Higher tape speeds or compression of the signal before recording allow sufficient video to be recorded without consuming an impractical amount of tape stock (Figure 9.12).

FIGURE 9.12 As of the writing of this chapter, the formats listed in the text discussion are in use. Each year new formats are developed and perfected, in some cases replacing earlier formats. Compatibility between digital formats is rare.

Signal Compression

The compression process removes redundant or repeated portions of the picture, such as the blue sky or white clouds. As long as there is no change in the hue, saturation, or luminance value, the digital program will “remember” the removed portions, then it will decompress and restore them when the tape is played back. This process saves space on the tape, disc, or chip, depending on the recording method. Compression allows a reasonable amount of programming material to be recorded, but the price is a slight degradation of picture quality.

The greater the compression, the greater the possible loss of quality. There are two basic systems now in use: JPEG, developed by the Joint Photographic Experts Group and originally intended for compression of still images, and MPEG, developed by the Motion Picture Experts Group and intended for compression of moving images. Each system offers advantages and disadvantages, and the possibility exists that new and better systems will be developed. Currently there are three MPEG systems: MPEG-1, MPEG-2, and MPEG-4. MPEG-2 was an improvement over MPEG-1, and MPEG-4 originally was written for interactive media intended for consumer use, but later developments have made the system applicable to HDTV and other high-quality and bandwidth-demanding formats (Figure 9.13). Additional MPEG standards have been developed by individual companies for their own equipment as technology continues to advance and develop.

FIGURE 9.13 To record and manipulate high-frequency video signals within a digital format, some method of compressing the signals needed to be developed to avoid requiring tremendous amounts of computer memory. Two basic systems and variations on those systems have been established, JPEG and MPEG. Researchers constantly work at developing newer systems that require less memory yet maintain the highest quality possible.

Digital Videotape Formats

D-1 was the first industry-accepted digital format. The Society of Motion Picture and Television Engineers (SMPTE), the organization that sets standards in the visual fields, agreed upon the D-1 standard in 1986. It has become the universal, component digital standard. The signal is recorded on a 19 mm oxide tape, offering the highest-quality and most flexible recording system, but also the most expensive. It is capable of recording compressed HDTV signals, but it does not compress standard signals. It is especially useful for multilayering graphics, animation, and feature film special effects.

D-2 was the second SMPTE standardized digital system, but it is a composite system. It also records on 19 mm tape, but it requires special metal tape. D-2 is less expensive than D-1, can be modified to record in the component mode, and is commonly used by broadcasters. Neither D-1 nor D-2 is practical for use in a camcorder because of the physical size of the tape transport system. D-3 and D-5 are compatible systems, even though D-3 was designed as a composite system and D-5 as a component system. Neither system compresses the video, and both use 12.5 mm (½-inch) metal tape. D-3 has a four-hour capacity on one reel, and D-5 offers two hours. D-5 is designed to record HDTV signals when the standards for that format are agreed upon.

Two systems created by competing videotape companies have not received standardization from SMPTE as of this writing. Both are being manufactured and are finding their individual markets. Sony developed Digital Betacam and Betacam SX to record on the same 12.5 mm metal tape stock as the Betacam SP recorder. They are also downward compatible with Betacam tapes. Digital Betacam is also a compressed component system compatible with the D-2 signal, but not with the D-2 tape.

Sony’s newest format is the XDCAM that records directly onto specialized flash memory cards called SxS. Panasonic’s highest level camera records onto its own flash memory cards, P2, a PCMCIA (Personal Computer Memory Card International Association) type card.

Since the late 1990s, nearly a dozen digital tape formats have been developed and marketed. D-6 records on a 19 mm tape designed for HDTV. D-7 (DVCPro) is one of the professional formats based on the consumer DV 6.35 mm format. Others are DVCAM and DVCPro50. In some cases, depending on the tape deck, the DV formats are compatible. Digital 8 is the digital version of the Hi8 format and is downward compatible with the 8 mm formats. D9, or Digital-S, is based on the S-VHS format and in some cases is downward compatible with S-VHS. Tape formats will continue to disappear as solid-state recording media replace the mechanical tape systems. MiniDV cassette recorders are designed to record video in one or more of the following digital formats: Panasonic’s DVC-Pro, DVCPro HD, DVSP (Canon and Sony DVSP formats are not completely compatible, however), Sony’s proprietary DVCam, and HDV. Many of these formats can be recorded in 24, 25, or 30 frames per second (fps) in either I (interlaced) or P (progressive) scan mode.

Tapeless Video Recording

Video and audio signals may be recorded in digital form without using magnetic tape. Digital pulses may be recorded on random access memory (RAM) chips within a computer. RAM chips are capable of recording as much as 128 MB per chip. With compression, over an hour of video material can be recorded on one chip. The next level of tapeless recording is offered by flash memory or USB cards or sticks. The same memory system used in cell phones, digital still cameras, and other digital devices works well for recording digital audio and video. Secure (SD), MultiMedia (MMC), CompactFlash (CF), Memory Stick, xD-Picture Cards, and Smart Media (SM) are all physically slightly different, but the information recorded on each is compatible without additional circuits or equipment. Most do not need external power; only the most powerful and those designed for rapid recording and play back may need an additional power source.

The advantages of impressing production information on computer chips and flash memory are instant access, no moving parts, no maintenance, and no need to shuttle through other information. In addition, there are no physical aberrations, such as dropouts, tracking, or skewing, in digital pulses. There are no problems of compatibility, only possible differences in compression standards between computer programs. Relatively inexpensive personal computers can replace expensive digital tape decks.

Many of the same advantages exist if the digital pulses are recorded on computer hard drives or flash rives. Hard drives are now designed to hold multiple terabytes (1,000 GB) and can be disengaged from the computer, stored, and moved to another computer. The removable feature provides an advantage if more than one project is assigned to the same computer and for archiving the material. Write-once-read-many (WORM) CD and DVD optical discs also offer the same advantages, except that once they are recorded they are not erasable. Erasable and reusable optical discs, called direct-read-after-write (DRAW), exist. Prices for professional- and consumer-quality disc recorders have lowered to the point that CDs and DVDs are now an affordable and practical means of recording digital information on permanent or reusable discs.

FILM RECORDING

Basic Photochemistry

Photography uses light energy to transform the chemical properties of light-sensitive substances. Photographic film consists of light-sensitive materials, such as silver halide crystals or grains, attached to a flexible support base such as cellulose acetate. Silver halide forms an invisible latent image when it is exposed to light in a camera. Light stimulates a chemical change in silver halide crystals, which can only be made visible and permanent by developing the image in certain chemical solutions. The film image appears dark or opaque where it was struck by light and clear where the light energy was not strong enough to stimulate the silver halide crystals. The resulting image is called a negative image. It inverts the whites and the blacks of the original scene. A white wall appears black and a black curtain appears white (Figure 9.14).

FIGURE 9.14 Black-and-white film consists of a layer of light-sensitive material, a flexible base, and an antihalation backing layer to prevent light from reflecting back through the base to the emulsion. Reversal film requires additional processing to create a positive image rather than a negative image.

To get a positive image, which reproduces the whites and blacks of the original scene, the negative film must be printed or copied onto another piece of film on a device called a contact printer. When the copy is chemically developed in the same manner as the negative film from which it was printed, it reproduces the correct whites and blacks. The bright areas in the original scene are now white and the black areas are black. This method, in which a negative is copied to produce a positive image, is called the negative/positive process.

An alternative approach to this two-stage, negative/positive process is known as the reversal process. The difference between negative/positive and reversal film is similar to the difference between snapshots and slides in still photography. Reversal recording is a single-stage process that produces a positive image after one development of the originally exposed film. The negative image resulting from initial exposure is converted to a positive image during several stages of development.

Reversal film produces a positive image immediately. It does not have to be printed to view the original scene, as does negative film. The size and composition of the silver halide crystals in large part determine the overall light sensitivity and graininess of the film stock.

Light sensitivity or film speed is rated in EI, which stands for exposure index. The American Standards Association rating, called ASA (or EI), or a German standard, called DIN, is often printed on the film package. These indices of a film’s overall sensitivity to light provide a relative indication of how much light will be required to properly expose a specific container of film. Slower films, with lower numbers, require more light than those with higher numbers (Figure 9.15).

FIGURE 9.15 The label on a film canister provides all of the information the camera operator or director of cinematography needs to adjust the camera and make exposure decisions. The EI numbers indicate the film speeds for daylight or tungsten lighting, and the other numbers indicate the type of film (the left can is 7278, a high-speed, black-and-white reversal film sock), batch numbers, inventory, and order numbers.

The term graininess refers to the size and visibility of particles in the film. A grainy image is one in which these particles are readily visible, and a fine-grain image is one in which they are not. Faster film stocks, which are more sensitive to light and therefore have higher EI numbers, generally have more visible grain structures than slower films, producing grainier images.

The size of the grain in the image can affect its resolution and sharpness, terms that refer to image clarity. Slower film tends to have higher resolution and sharpness than faster film. The size of the film grain also will determine the film’s latitude, or the ability to reproduce a wide range of reflected light. Better films are able to reproduce an image in lighting with a 100:1 contrast range, but a standard video camera pickup tube has an effective contrast ratio of 30:1, and a video camera chip has a ratio of 50:1. If there is a wide range of dark-to-light reflecting objects in a scene, a video camera will not record as wide a range of grayscale as film. Many neutral tones will be recorded as completely black or completely white rather than as some shade in-between. In film, a full range of tones may be recorded. The effect of contrast ratio on lighting and scene design is discussed more fully in Chapter 7, Lighting and Design, because the difference between lighting for film and video is important (Figure 9.16).

FIGURE 9.16 The contrast ratio of a medium determines how wide a variation in light reflectance values that medium can reproduce without losing either the brightest or the darkest values. Any attempt to reproduce a subject or frame containing a higher contrast range than the medium is capable of reproducing will result in either muddy dark areas or flared-out white areas.

Color Film

We have so far considered only the recording of different brightness levels of light on black-and-white film. Color film responds to different hues and saturations of light, as well as different levels of brightness. A color-film emulsion consists of a multilayered suspension of light-sensitive particles and color dyes attached to a flexible support base, such as cellulose acetate. When light enters a camera, it strikes three different layers of color dyes and light-sensitive particles. These layers are sensitive to blue, green, and red light, respectively. Light first strikes the blue-sensitive layer, where only the blue light affects the particles and dyes. The other colors of light then pass through this layer and a yellow filter, which removes excess blue light, before striking the green- and red-sensitive layers. These layers are sensitive to blue light as well as their own wavelength bands. The blue-sensitive layer thus records the blue component, the green-sensitive layer records the green component, and the red-sensitive layer records the red component of white light (Figure 9.17).

FIGURE 9.17 Color emulsion film layers alternate specific color-sensitive layers with opposite color-dye layers. This produces a negative reproduction of the image exposed to the camera. Color reversal film, like black-and-white reversal film, requires additional layers and processing. Like black-and-white film, color film stocks come in negative or reversal processes and a variety of light sensitivities and contrast ranges.

Film Exposure

Film is exposed inside a lightproof mechanism called a camera body. A basic film camera consists of a lens, which focuses an image on the film; a viewfinder, which allows the camera operator to see the image that is being recorded; a film feed and take-up mechanism, which supplies film to the exposure area and rolls it up after it has been exposed; a motor, which drives the film through the camera; a rotating opaque shutter, which rapidly opens and closes to expose each frame of film; an aperture, which determines the dimensions of the frame that is exposed; a pressure plate, which holds the film flat against the aperture to ensure good focus; a pulldown claw, which intermittently grabs film sprocket holes or perforations to advance the film for each single frame or still photograph at the aperture; a speed control, which determines how many individual frames will be exposed each second; and a run/stop button, which turns the camera on and off.

Motion-picture film is perforated at regular intervals so that a camera and a projector can drive it intermittently. This intermittent movement allows a single frame of film to be held stationary while a rotating shutter opens up and allows light passing through the lens to expose the film. A projector uses the same mechanism to project recorded images through the lens onto a screen. The feed and take-up mechanisms push the film continually through the camera, whereas the claw pulls the film at the aperture. Film is constantly pushed and pulled through a 16 mm camera at a rate of 36 feet per minute, or through a 35 mm camera at 90 feet per minute. Normal sound speed exposes 24 frames per second (fps) in 35 mm, 16 mm, and Super-8 mm.

The camera shutter and claw must be synchronized so that the shutter stays open when the claw disengages the film and retracts behind the aperture plate. At this point, the film is stationary in the aperture. Sometimes it is held stationary by a device known as a registration pin, which holds the film in firm registration—that is, it holds it very steady when it is not being pulled by the claw. The shutter must be closed when the registration pin retracts and the claw engages the film to advance it, or the film images will blur as they pass the light in the aperture.

The speed control allows the camera operator to alter the frames-per-second speed of the camera. Film recorded at speeds above 24 fps will reproduce images in slow motion when it is projected or played back at normal sound speed (24 fps). Camera images recorded at fewer than 24 fps will produce fast motion. Thus, slow and fast motion are produced during actual recording in film, unlike video recording, which always occurs at 30 fps. Increasing the film recording speed also changes the synchronized shutter speed and affects the amount of light exposing the film. Faster recording speeds produce more rapid shutter speeds and less light reaches each frame during exposure, because the duration of each exposure is reduced. To compensate for these changes in exposure, the lens must be adjusted so that more light passes through it and strikes the film when the camera speed is increased.

Motion Picture Formats

Motion picture film, which is exposed to light inside a camera, is available in a variety of formats or film widths, including 8 mm, 16 mm, 35 mm, and 65 mm formats. These distinctions between various formats refer to the width of the film in millimeters. The width of the film affects image size and quality, as well as the cost of supplies and equipment. There used to be two 8 mm formats: standard 8 mm and Super-8 mm. Super-8 mm cameras record images that are 50 percent larger than those of standard 8 mm cameras. Standard 8 mm is now virtually obsolete. All subsequent references in this book are to Super-8 mm, which is sometimes used for home movies, as well as for some independently produced, low-budget films.

The 16 mm format has been widely used for professional recording of industrial, educational, governmental, and documentary films, as well as some commercials and low-budget feature films, but now videotape productions are competing for the same markets. Some resurgence in the use of 16 mm film has come from new developments in Super-16. Such films are easily transferred to a video format for 16:9 wide-screen broadcast on television and cable. Network-level commercials and television programs are recorded in 35 mm, as are most feature films. Some feature films are recorded on 65 mm film, which is then printed onto 70 mm film, with the added 5 mm being the width of the soundtrack area, for projection in large, specially outfitted theaters. Other 70 mm film prints for projection are enlargements or blowups from original 35 mm recordings (Figure 9.18).

FIGURE 9.18 Virtually all professional film now comes in one of three formats: 16 mm, 35 mm, or 70 mm film. Super-8 is still available for consumer use, and special large feature film formats also are in use such as IMAX, a wide-screen format.

Film stocks are available in different film lengths and loading arrangements or configurations. Super-8 mm film comes in a lightproof cartridge and is exactly 8 mm wide. It is normally packaged in 50-foot lengths, which lasts for two minutes and 46 seconds. Sixteen-millimeter film is available on daylight spools, which contain 100, 200, or 360 feet of film. It is also available on plastic cores, which simply provide a firm center on which the film is wound but do not protect the edges of the film from light. Film that comes on a core must be loaded in complete darkness. The standard length of 16 mm film cores is 400 or 1,200 feet. One hundred feet of 16 mm film, when exposed at 24 fps, runs for two minutes and 46 seconds. Thirty-five-millimeter film comes on cores in standard lengths of 100, 200, 400, and 1,100 feet. Ninety feet of 35 mm film runs for one minute at 24 fps.

Film stocks differ in terms of their perforation or sprocket-hole sizes and placements. Super-8 mm film has sprocket holes on only one side of the film, whereas 16 mm films are available with single-sided or double-sided perforations, which are called single-perf and double-perf, respectively. Magnetically striped 16 mm film has audio track in place of one row of sprocket holes. Thirty-five-millimeter film is always double-perf.

Film Sound Synchronization

Synchronous sounds match their visual sound sources and are usually recorded at the same time as the corresponding visual images. Many different systems have been developed to synchronize recorded visual images with recorded sounds. Early in the 1950s, portable ¼-inch reel-to-reel tape recorders had the capacity to record a sync signal that allowed them to be used in conjunction with a motion picture camera. Today, separate digital recorders are used because they run to absolute speed and do not have to be connected to either the video or film camera to maintain sync, as long as the film camera receives a sync signal from a crystal control or the video camera is locked to its sync signal. This allows the separate recording of sounds that are synchronous with their corresponding pictures.

Single-System Film Recording

There are basically two different systems of synchronous sound film recording in common use today: single system and double system. Single-system recording, as shown in Figure 9.19, puts sounds and images on the same piece of film; usually, the sound is recorded on the edge of original motion picture film.

FIGURE 9.19 Cameras that record sound simultaneously with the exposing of the film are called single-system cameras. The sound-recording head must be located apart from the aperture, because the two cannot be physically located at the same place within the body of the camera. The sound head on a 16 mm single-system is located 28 frames ahead of the aperture. This separation must be taken into consideration when shooting original film to edit without transferring the sound to another medium.

This technique is called sound-on-film (SOF). As a general rule, 35 mm film is not used for sound-on-film or single-system original recording. Sixteen-millimeter magnetic sound-on-film is recorded 28 frames ahead of the picture gate or film aperture. (Sixteen-millimeter optical sound-on-film is 26 frames ahead of the picture. Optical sound is created by exposing the edge of the film to light.) Super-8 mm sound-on-film is recorded 18 frames ahead of its corresponding pictures. These standard intervals allow the film driven through a camera to change from an intermittent movement at the film aperture, where a rapid series of still frames are recorded, to a continuous movement over the sound-recording head. The same 28-, 26-, or 18-frame advance of sound ahead of the picture is standard in most 16 mm or Super-8 mm film sound projectors.

Single-system sound is commonly used for exhibition purposes. The final film prints marry an optical or magnetic soundtrack with their corresponding pictures on the same piece of film.

Single-system recording is used extensively in small formats, such as Super-8 mm film recording. Editing problems arise from the fact that the sounds are always a specific number of frames ahead of the corresponding pictures. Sound-on-film yields an initial sound recording that is decidedly inferior in audio quality to a double-system film sound recording. If SOF is to be edited, either it must be shot with pauses in the voice track, so edits can be made without losing portions of the sound, or the soundtrack must be dubbed to a separate piece of film for double-system editing.

Double-System Film Recording

In double-system synchronous sound recording, the sounds and images are recorded on separate materials. (This approach is normally used for production and editing but not for final projection.) Rather than recording sounds directly on the edge of the film during production, an independent tape recorder is used, which can record and play back sound in exact synchronization with the corresponding images. There are two basic systems for synchronizing the recording of the separate sounds and pictures; the choice depends on both the camera and the recorder’s speed as controlled by cable sync and crystal sync (Figure 9.20).

FIGURE 9.20 The camera and sound recorder stay in synchronization because they are both running with internal crystal sync or a synchronizing cable connects them.

Cable sync refers to the use of an electrical cable, which connects the camera to the tape recorder like an umbilical cord. The cable carries a 60-cycle-per-second sync signal, called Pilotone, which is generated by the camera. The Pilotone is recorded on the audiotape by a special sync head on the audiotape recorder. Crystal sync allows the camera and the tape recorder to be physically separated. This can be a distinct advantage because it increases the flexibility, mobility, and independence of sound and picture recording machines and operators, who are otherwise linked by an umbilical cable. For crystal sync, a crystal oscillator controls the speed of the camera so that the film is driven at a precise speed of 24 fps. The analog audiotape recorder uses a separate crystal oscillator to place a sync signal on the audiotape so that its original recording speed can be duplicated during playback and a digital recorder runs true to speed. Digital audiotape recorders also can be synchronized to film cameras using sync signals or the stable recording speed of a digital recorder to maintain sync.

Slating

Creating a common point where separately recorded elements of sound and picture match is called slating. In video recording, this generally is not necessary because the audio is recorded directly onto the tape as the picture, but it does provide a means of accurately logging scenes as they are shot. Normally a slate, sometimes called a clapstick or clapboard, is used for this purpose in motion picture production. The clapboard consists of a piece of wood with a hinged arm that makes a clapping sound when it strikes the bottom portion of the clapboard. This device produces a loud, recorded sound that can be matched to the corresponding visual image of the closing arm (Figure 9.21).

FIGURE 9.21 After both the camera and the recorder have reached speed, a production assistant holds the clapboard in front of the camera. The board contains information indicating the shot and take numbers, director and camera operator’s names, and other information critical to the shot. Once speed has been reached, the assistant snaps the clapper shut smartly, creating a sharp, intense sound and a visual record that will be used to sync the film and soundtrack later during the editing process.

In the absence of a clapboard, a person can call out “Slate!” followed by a sharp handclap. If the separate sound and picture tracks are perfectly matched at the beginning of a shot, the editor can be reasonably sure that the entire cable or crystal-sync recorded shot will maintain synchronization. Slating is also used to identify the project title, director, and shot and take numbers during single-camera film or videotape recording. This information is written on the chalkboard surface of the slate or clap-stick and is read aloud at the beginning of each camera shot. Thus, each take is fully identified on the film or videotape and the audiotape.

Some film cameras are designed for documentary shooting in situations where the use of a clapboard is impractical. They have an electronic means of providing a reference synchronization point for editing, called an automatic slate. At the beginning of each camera take, the first few frames (usually the first eight) of a picture are flashed or fogged with a small light inside the camera, and a signal that is separate from the Pilotone is sent to the tape recorder either by cable, if cable sync is being used, or by radio transmitter, if crystal sync is being used. This signal triggers a clap alarm, which creates an audible tone, known as the bloop. The proper flash frame of the picture can then be matched to the bloop at the beginning of the shot for editing synchronization.

Another development in slating is the electronic clapboard, which generates a tone that is fed to the camera and recorder and illuminates a continuously running SMPTE timecode visible to the camera and recorded on the edge of the film or on the videotape.

SUMMARY

Understanding the technology that makes audio, video, and film recording possible helps us to obtain better-quality images. Recording media are based on digital, optical, electronic, and photochemical recording processes. Film uses a subtractive mixing process, with cyan, magenta, and yellow filters embedded in different layers of the film to subtract different color wavelengths from a white light source and to thereby produce a variety of colors on a screen. A video camera records and transmits visual images electronically using an additive color process of mixing red, green, and blue light to produce color video.

Videotape and film recording materials are available in a variety of formats. Among helical scan recorders, VHS videotape recorders use ½-inch (8 mm) videotape, whereas others use 6.35 mm (¼-inch), 8 mm (⅓-inch), 12.5 mm (½-inch), or 19 mm (¾-inch) videotape. Digital recorders use tape from 6 mm to 19 mm wide. Super-8 mm, 16 mm (which includes Super-16 mm), 35 mm, and 65 mm film require different cameras and recording equipment. Some ¼-inch videotape formats, such as DVPro, MiniDV, and DV CAM, reproduce high-quality images, but digital videotape recorders, from D-1 through D-9 and newer formats, provide even higher quality images. Four tape formats specifically designed for high definition are available: D5-HD, based on D-5; D7-HD, based on DVCPro; D9-HD, based on Digital-S; and HDCAM HD, which provides the highest-resolution videotape images. IMAX provides the highest-resolution film images.

The aesthetic use of recorded sounds demands an understanding of recording devices and their selection. Audiotape is available in a variety of formats in terms of tape sizes (widths and thicknesses) and tape enclosures, such as audiocassettes. An analog audiotape recorder converts the electrical audio signal to magnetic pulses stored on magnetic recording material. Digital recordings consist of a series of on-and-off pulses and are less susceptible to recording problems, such as cross-talk, print-through, and fading, than are analog signals which record the entire electrical signal. Tape speed directly affects the amount of tape consumed, and higher speeds generally produce higher-quality recordings. In general, the larger the tape size and the faster the speed, the better the quality of the recorded sound.

Film contains silver halide crystals, which form a latent image when they are exposed to light. These latent images become visible through chemical processing. There are two basic film development processes, negative and reversal, which are analogous to color prints and slides in still photography. Film generally has a wider contrast ratio than video. Some film stocks, such as color negative, can record and differentiate brightness levels that are more than 100 times as bright as the darkest object in a scene, yielding a contrast ratio of 100:1 or 200:1. The maximum contrast ratio in video is usually 30:1 or 50:1.

Film sound and images can be recorded on the same piece of film, which is called single-system sound-on-film (SOF) recording, or they can be recorded on separate sound and picture mechanisms, which is called double-system film sound recording. Double-system recording allows for more editing flexibility than single-system recording. Slating refers to the placement of a common starting point on the picture and sound recordings. It is also used to identify the project title, director, and shot and take numbers during single-camera recording.

EXERCISES

Additional Readings

Alten, Stanley, 2008. Audio in Media, eighth ed. Wadsworth, Belmont, CA.

Ascher, Steven, Pincus, Edward, Keller, Carol, 1999. The Filmmaker’s Handbook: A Comprehensive Guide for the Digital Age, Plume, New York.

Baxter, Dennis, 2007. A Practical Guide to Television Sound Engineering, Focal Press, Boston.

Cianci, Philip J., 2007. HDTV and the Transition to Digital Broadcasting: Understanding New Television Technologies, Focal Press, Boston.

Collins, Mike E., 2001. ProTools: Practical Recording, Editing, Mixing for Music Production, Focal Press, Boston.

Crich, Tim, 2005. Recording Tips for Engineers: For Cleaner, Brighter Tracks, Focal Press, Boston.

Hodges, Peter, 2005. An Introduction to Video and Audio Measurement, Focal Press, Boston.

Huber, David Niles, 2001. Modern Recording Techniques, fifth ed. Focal Press, Boston.

Maes, Jan, Vercammen, Marc, 2001. Digital Audio Technology: A Guide to CD, MiniDisc, SACD, DVD(A), MP3, and DAT, Focal Press, Boston.

McDaniel, Drew, et al, 2008. Fundamentals of Audio Production, Allyn & Bacon, Boston.

Moylan, William, 2006. Understanding and Crafting the Mix: The Art of Recording, second ed. Focal Press, Boston.

Rose, Jay, 2008. Producing Great Sound for Film and Video, third ed. Focal Press, Boston.

Rumsey, Francis, McCormick, Tim, 2002. Sound Recording: An Introduction, fourth ed. Focal Press, Boston.

Talbot-Smith, Michael, 2000. Sound Engineer’s Pocket Book, Focal Press, Boston.

Watkinson, John, 2002. An Introduction to Digital Audio, second ed. Focal Press, Boston.

Watkinson, John, 2004. The MPEG Handbook, second ed. Focal Press, Boston.

Watkinson, John, 2008. The Art of Digital Audio, fourth ed. Focal Press, Boston.

Weis, Elizabeth, Belton, John, 1985. Film Sound: Theory and Practice, Columbia University Press, New York.

Wooten, Cliff, 2005. A Practical Guide to Video and Audio Compression: From Sprockets and Rasters to Macro Blocks, Focal Press, Boston.

Yewdall, David Rush, 2007. The Practical Art of Motion Picture Sound, third ed. Focal Press, Boston.