TECH TIPS

Sounding Off About After Effects
Incorporating Audio Files into AE Projects
by Bill Stetz

After Effects is not the feature-rich application that a sound designer would like, yet it still holds some special features for incorporating sound into your projects just the same. As long as the AE project user adheres to some conventions, After Effects can use and embellish sound files in any project. While editing sound inside an After Effects project is not the ideal situation, it is still possible.

From a nuts-and-bolts starting point, sound files are imported into After Effects just like still and motion files are. You may use the File->Import->File menu command to open a dialogue box to navigate to your audio file, or simply drag the audio file from the desktop or disk file window into the project resource list. In any case, once the file reference appears in the resource list or project list, it becomes accessible to any composition in the After Effects workflow.

Remember, just like any video or still file that you use in an After Effects project, the sound file in your project list is only a reference to the actual file that the AE uses. That is, your sound file is not embedded in the project or composition; only a reference to where the sound file exists on your disk drive is established. Remember to take your sound files with you if you happen to move your work files from computer to computer.

Highlight the sound file in the project resource list by clicking on it; file characteristics are noted such as the duration of the sound cut, the sampling rate, the file bit rate and mono or stereo designation (See figure 1). This is the best first step in determining if your have the proper file and file format included in your project.


Fig. 1 Highlighting the audio file in the AE project resource list reveals info about the file as in this example, clip duration (eight minutes, 28 frames), sampling rate of 48,000 khz, 16-bit sampling size and stereo file type.

Certain sound file references will import into After Effects projects and even play back in preview, but they may not render properly and will in some cases cause your project renders to playback erratically or even stop. Most notably, MP3 files (which is an iteration of the MPEG format) will not play back properly in your AE renders and should not be used.

I cannot stress this more emphatically, because the prevalence of MP3 files on the internet and the ease of dragging an MP3 into your project makes it an overlooked snag in the production flow of a project when it is inevitably determined that the project will not produce a usable file after the render step. The common defects produced by using incompatible sound files in your AE projects will be click sounds and motion playbacks that falter or stop.

The preferred sound file format is the aif or AIFF file format (Audio Interchange File Format). Most if not all sound file formats may be converted to AIFF files using one or another applications. MP3 files may be converted to AIFF as well. The most straightforward way of converting an audio file to AIFF files is to open the sound file in QuickTime player and use the File->Export command, the user is presented with a dialogue box that allows you to apply the new file name, the location window of where to save the file and, most importantly, the pop-up box of choosing the sampling rate and mono or stereo options (See figure 2).


Fig. 2 Using QuickTime Player to export audio files to aiff format allows saving the audio files at a new sampling rate or under a new compression scheme.

Resaving a compressed sound file at a higher sampling rate is not going to improve the quality of the sound file. It simply resaves that file at a new rate and format. But it does allow you to conform your files all to the same format if that is desirable. Sound files, like image and digital video files, may be compressed, but no “up-conversion” of any compressed file is going to replace the lost information that was squelched in the original compression. That’s a hard rule that dictates the good advice of starting with the best file quality for your project to get the best quality out. Any computer geek will read that advice as GIGO (Garbage in, garbage out).

Aside from these particulars, After Effects treats your sound file like other layers in the composition window. A sound file added to a composition will have its own layer and may be slid, cut, manipulated in time, turned on and off, hidden and previewed. The way audio files are previewed adds a wrinkle to working in AE.

Unlike visual motion layers that are previewed in After Effects by pressing the space bar, dragging the time cursor over a section or pressing the RAM preview button, sound is not previewed in any of these ways. For whatever the reasons of the application designers, sound may be previewed in real time only by pressing the period (dot) key in the numeric keypad of the keyboard. That presents a bit of an inconvenience for laptop users who don’t have numeric keypads on their keyboards. (This is circumvented by pressing the numbers lock key and the period of the standard keyboard layout). Then preview of audio is limited only to eight seconds of the timeline from the start of the work area. This happens to be a program default setting that may be changed in the After Effects preferences.

Audio may be scrubbed as well. This feature is performed by holding the Command key (Mac) or the Alt key (PC) down while dragging the timeline cursor over the sections that you want to scrub. For those not used to sound editing, some practice may be needed to determine what section of audio you are listening to while scrubbing.

Lastly, you can preview the audio in real time with the video in real time only by pressing the RAM preview button. That will get you a few seconds of preview from the start of your work area as demarked by the work area bar, but since the length of preview is limited by the memory reserves that your particular system has, you probably won’t be seeing and hearing more than a few seconds of preview.

Beside these three audio preview methods, the most sure way to preview a section–although more time consuming–is to render the project or work area out as a movie with audio either in full resolution or less to determine the effect of the sound and picture together.

(As useful and flexible as After Effects is, it is a bit clumsy and negligent in its preview and transport of audio. The makers of After Effects still hold a tight grip on touting one of the most innovative and flexible applications for the visual motion graphics arena, but they certainly never claim to be all things to all users, and rightly so. Audio design work is done more effectively outside of this program, but there still exist some clean solutions within After Effects for completing small projects start to finish.)

Audio effects, just like visual effects, are found in the Effects menu of the main application. Audio effects have their own submenu and are limited to the most basic of effects. (After Effects Professional edition effects are listed in this article. If you work with After Effects Standard edition, certain of these effects described may be missing from your application.) These effects are:

Backwards. Very simply, this effect, when applied to a particular audio layer, plays that audio layer in reverse. Placement of the layer does not change; last note first, first note last.

Bass & Treble. The Bass and Treble effect lets you adjust the amount of boost or cut applied to the low frequencies (bass) or the high frequencies (treble) of the audio layer. If you need greater control in working with audio tone, use the Parametric Equalization effect (see below) in the After Effects Professional edition.

Delay. The Delay effect repeats the sounds in the audio layer after a specified amount of time. This simulates sound bouncing off a surface, such as a wall some distance away.

Flange & Chorus. The Flange and Chorus effect lets you adjust both the Flange and Chorus. Flange applies a copy of the sound that is detuned, or played at a frequency slightly offset from the original. By experimenting with the voice separation time and the modulation depth, you can create a wavy, rushing sound. The default settings apply to Flange alone. Chorus is commonly used to add depth and character to audio footage that contains a single instrument or voice. Chorus makes one voice sound like many.

High-Low Pass. This effect sets a limit above or below which frequencies can pass. The High Pass filter option allows frequencies above the limit and blocks frequencies below. Conversely, Low Pass allows frequencies below the limit and blocks frequencies above.

Modulator. The Modulator effect adds both vibrato and tremolo to audio by modulating (varying) the frequency and amplitude. Using Modulator, you can create a Doppler effect, such as when a train whistle gets higher in pitch as it approaches an observer, and then drops in pitch as it passes.

Parametric EQ. The Parametric EQ effect either emphasizes or attenuates specific frequency ranges. Parametric EQ is useful for enhancing music, such as boosting low frequencies to bring up bass. Using this effect, you can enhance up to three different bands of the audio footage.

Reverb. The Reverb effect approximates a spacious or acoustically live interior by simulating random reflections of a sound off a surface.

Stereo Mixer. The Stereo Mixer effect mixes the left and right channels of an audio layer and pans the entire signal from one channel to the other.

Tone. The Tone effect synthesizes simple audio tones to create effects such as the low rumble of a submarine, a telephone ringing in the background, sirens or a laser blast. You can add up to five tones for each effect to create a chord, for example, in a composition. When you apply this effect to audio footage, the dry (unprocessed) audio is ignored, and only the tone plays.

Remember that the beauty of After Effects and its simple interface of layers and effects allows the operator to control these effects with keyframes that determine when an effect starts in a layer, and holds the parameters of all the variables of that effect and marks where the effects end or blend over time.

On the layer level, audio may be viewed in a visual waveform to find peaks of levels and starts and stops of cues (See figure 3). This overview allows the user to make general shifts and changes to the audio and the effects provided are more than enough to clean up and enhance a short-form work or be used for timing when in a visual work.


Fig. 3 Revealing the waveform model of an audio layer gives a visual representation of the level of the audio clip at any frame along the composition timeline.

Finally, don’t forget that sound is not generally output to your rendered After Effects project files. If audio is desired as part of the finished movie file, the audio portion of the project must be “turned on” each time a render occurs. This switch is located in the Output Module screen of the render cue. Once audio is turned on to be included, the operator has the option to resample the audio output that accompanies the movie to a higher or lower sampling rate, a stereo or mono format or any of a number of compression schemes (See figure 4). To maintain the best quality of your audio output, make sure that the audio settings are set to the highest level of sampling rate and the file format of the best quality audio file included in your project.

Bill Stetz is the art director of Editors Guild Magazine. He is also an instructor of motion graphics at the Art Institute of California, Los Angeles in Santa Monica and has worked as a sound recording assistant to Tom Holman, developer of the THX Sound System for George Lucas. He can be reached at design@clik.net.

Sounds of Note

Reproduction of sound has been adopted using many different techniques and devices since the first recording and reproduction of sound. With regard to motion pictures, the first synchronized sound was introduced as mechanical interlocks between the motion picture projector and recorded discs or records. Warner Bros. first adopted this method with the Al Jolson film The Jazz Singer. Interestingly, this technique of separate visual and audio reproducers in synchronization was used many years later (as late as the 1990s) with theatre systems that used film projection equipment and a separate CD audio soundtrack which were synchronized and projected to theatre audiences–although these systems are not widespread or popular now.

About the same time that the first record-projector interlock systems were introduced (the mid- to late 1920s), others were perfecting sound reproduction that was recorded directly onto the motion picture film ensuring perfect synchronization and eliminating the mishap of record needles skipping and putting the film and sound out of synch. Joseph Tykociner at the University of Illinois and, separately, Dr. Lee deForest developed the technique of recording FM (frequency modulation) sound waves on the film. Although Tykociner demonstrated sound-on-film as early as June 1922, deForest is substantially credited for the invention at a later date (1929).

All of these techniques involved recording and reproducing sound by analog methods. That is, the sound which is carried in continuous waves of vibrations is recorded in continuous waves by the analog path of 1) sound source to 2) microphones to 3) amplifiers to 4) tape or disc or film. The reproduction of the sound follows a reverse analog path of 1) tape or disc or film passing 2) a reproducer such as a magnetic tape head or a needle or an optical reader that 3) passes its record to an amplifier and then to 4) a reproducer or speaker. The speaker reproduces the vibrations of the original sound to the best of its design capabilities.

Digital sound is different; not in how we hear it or even so much as how it is reproduced, but in how it is recorded or preserved, processed and delivered. Computer hard drives hold information in bits and bytes of data. The bits that make up bytes of data are simply collected indices of “on” and “off,” or 0s and 1s. If you can read enough of these indices, one can code letters of the alphabet and spell words that can be displayed on a computer screen or saved and interpreted as passages or letters or books or encyclopedias with bytes of information recorded magnetically (or optically). While it takes a lot of bytes of digital information to reproduce all the words of a book or encyclopedia, it may be done.

Now imagine that digital audio is more demanding of the digital medium to reproduce sound instead of words by a much greater factor because much more information is being recorded. And, it is being recorded in bits of information (read 0s and 1s). Imagine trying to reproduce the sound of birds singing with 0s and 1s. How can that be done? With a lot of information. Digitally, sound is stored as these 0s and 1s or bits of information at the rate of 44,100 times per second for CD quality audio and 48,000 times per second for video sound. That is, in the instance of CD quality audio, digital sound is recording a sample of the sound waves once every 44,100th of a second to make up the sound reproduction that you hear. This is still not a continuous wave of sound but definite, separate bits of information that is recorded and then reproduced.

In this sense, the old LPs that you store in the garage, or long ago threw away, actually reproduce sound more faithfully than your CDs on a CD player because they reproduce sound in continuous uninterrupted waves of sound rather than separate closely timed bits of information. Although the rates at which digital audio are recorded are so high that people cannot discern the gaps of digital information, those gaps are nonetheless there. Current audio recording techniques (digital, that is) generally sample sound at 96,000 cycles per second or higher although the reproduction of that sound is generally limited to 41,100 by the delivery technology of the Compact Disc.
Bill Stetz

[ return to top ]