Module 44B

Part II

Audio

Recording,

Editing and

Playback

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DAT

DATs (digital audiotapes) are capable of audio quality that exceeds what's possible with CDs.

The 2-inch by 2-7/8 inch (5 X 7.6 cm) DAT cassette contains audiotape 3.81mm wide. The cassette (shown below) is about two-thirds the size of a standard analog audiocassette. The two-hour capacity of a DAT cassette is 66 percent greater than a standard 80-minute CD.

RDAT (recordable digital audiotape) is designed for professional applications, as are the very high quality ADAT machines (types I and II). 

DAT systems use a headwheel that spins at 2,000 rpm (revolutions per minute), similar to what's found in a videocassette recorder.

Various types of data can be recorded with the audio.  Examples are time code and the MIDI machine control data used in sophisticated postproduction audio work.

DAT Time Code

The DAT time code system, referred to as the IEC Sub-code Format, also insures that tapes recorded on one DAT machine can be played back without problems on any other machine. DAT time code is similar to the SMPTE time code that we'll discuss in the sections on videotape editing.
 

Computer Hard Drives

Today, computer hard drives are the choice for broadcast music, commercials, and general audio tracks. Recording audio material on computer hard drives (generally with MPEG-2 or MPEG-4 compression, see below) has several advantages.

First, the material can be indexed in an electronic "table of contents" display that makes it easy to find what you need. This index can also list all of the relevant data about the "cuts" (selections) -- durations, artists, etc. Second, you have almost instant access to the selections.

Once recorded on a hard drive, there is no wear and tear on the recording medium as the audio tracks are repeatedly played. Another advantage is that the selections can't be accidentally misfiled after use. (If you've ever put a CD back in the wrong case, you know the problems this can represent.) And, finally, unlike most CDs, hard drive space can easily be erased and re-used.

Although hard drives are extremely reliable today, they do occasionally "crash," especially after thousands of hours of use or a major jolt ends up damaging the delicate drive and head mechanism.

Unless anti-virus measures are instituted, the computer operating system can also be infected with viruses, which can result in a complete loss of recorded material. With these things in mind, critical files and information should always be "backed up" on other recording media.
 

IC and PC Card Recorders

Some audio production is now being done with PC card and IC recorders. Both use solid-state memory cards, such as CompactFlash and ATA Cards.

These memory cards contain no moving parts and are impervious to shock and temperature changes.

The data in these memory modules can be transferred directly to a computer for editing.

These units typically give you the choice of two basic recording formats: MPEG-2, a compressed data format, and PCM (pulse code modulation) which is an uncompressed digital format. The latter is used with CD players, DAT recorders, and on computer editing programs that use wave (.wav) files.

RAM Audio Recorders

As shown on the right, this new generation of recorders can be a fraction of the size of other types of recorders.

However, unlike recorders with removable media, the stored audio must generally be played back from the unit, itself.

The iPod Era

When iPod-type devices and computers that could "rip" (copy) musical selections from CDs and Internet sources arrived on the scene, consumer audio recording and playback changed in a major way.

Users can assemble hours of their favorite music (up to 2,000 songs) on a computer and transfer it to a pocket-sized, solid-state listening device such as an iPod (on the left) or to one of the new generation cell phones (on the right).

"Podcasts" of broadcasts from TV networks (photo on the left) can also be downloaded and listened to or viewed at the user's convenience.  

With the iPod nano you can watch up to 5 hours of TV shows, music videos, movies, and podcasts.

Although Apple Computer initially popularized these devices, many manufacturers now produce their own versions.

Audio Editing Systems

Audio editing used to require physically cutting and splicing audiotape — an arduous process.

Today, there are numerous computer-based audio editing programs available. Many are shareware that can be downloaded from the Internet.

Shareware can be downloaded and tested, generally for about a month, before the program quits working and you need to pay for it.

Once you pay, you may be given an unlock code that will enable you to use the program for an unlimited time.

Often, minor updates to the program are free; major updates will probably involve an update charge.

In addition to basic editing, audio editing programs offer audio filtering, manipulation, and an endless range of special audio effects.

The audio line above shows how a single channel of sound appears in an audio editor. The vertical red line indicates the cursor (selector) position.

Much as a cursor is used to mark words in a word processing program to make changes as needed, the cursor in an audio time line provides a point of reference for making audio changes.

 

The display above shows how the time lines are integrated into a typical audio editor. Most programs use a computer mouse to drag-and-drop segments and special effects onto a time-line (the longitudinal graphical representation of the audio along a time continuum).

Audio editing in television production is typically handled along with the video on a video editing system. This will be covered in more detail in Module 56.

The hard drives on computer-based audio editing systems can also store a wide range of sound effects that can be pulled down to a time line to accompany narration and music.