ARS 263
Intermediate Digital Media
Instructor: Barbara Lattanzi

last update 10.05


AUDIO DIGITIZING

This describes a series of steps for...

audio digitizing your recordings using Apple's Soundtrack Pro software.  These steps will prepare you for processing the files and for final mixing of multiple channels of sound in in Soundtrack Pro. After that the files can be used for other projects in Final Cut Pro, Flash, or other software application.

Note: You are using the analog output of Sony minidisc recorder to the Mac.  This manufacturer decision to engineer a digital audio recorder that outputs only an analog signal (instead of the digital recording itself) is a simple limitation to overcome.  It means that, in order to work with our audio recordings using computer software, we will need to, in effect, re-digitize the recorder's audio output.

There is also a useful description of audio basics (a pdf file)

1. You are about to cross the Digital-Analog-Digital Divide! What connects to what?

Rule of thumb: Send outputs to inputs and inputs to outputs.

Sony minidisc recorder has one "stereo mini" output jack:  the headphone jack.

Using a stereo mini audio cable, connect the output of the Sony minidisc recorder to the input of the iMac. (the jack just above the headphone jack).

2.  Check these Macintosh "System Preferences" settings:

• System Preferences: Click on sound icon
• Sound Input setting: Built-in Audio
• Sound Output setting: Built-in Audio
• Set the audio level on the Sound Input setting all the way to the right (maximum input volume).
  

3.  Open the audio processing program.  We are using Apple's "SoundTrack Pro". 

Note that there are many other audio editing programs are 'out there' for both Mac and Windows PC.  One popular and excellent Mac shareware program you can use is called "Cacophony".  One open-source, free software program that is available for the Mac as well as PC Windows is called "Audacity".

You must check the set-up preferences for SoundTrack Pro:

Soundtrack Pro > Preferences: select "Project"

The relevant settings are:

• Sample Rate: 48000 Hz (sometimes indicated as 48 kHz)
  (Note that in Final Cut Pro, we used 48000 Hz which is the sampling rate for DVD audio, but in compressing into Quicktime mpeg 4 we used 44100 Hz which is the sampling rate for CD audio and for mp3 audio)
• Export Bit Depth: 16 Bit (This is the same for DVDs and CDs)
• Video Frames per Second: 29.97

Soundtrack Pro > Preferences: select "Recording"

The relevant settings are:

• Check input as "Built-in Audio"
• Check monitor as "Built-in Audio"
• (leave the "latency compensation at 0 milliseconds)
• Sessions Location: select "Choose..." button and create a folder on your external hard-drive (or on computer hard-drive, to later copy to your external hard-drive)

Save the project, even before you have done anything else. (This is similar to the way you start a Final Cut Pro project):

File > Save as...

example file: myaudioproject.stmp

(Note that the proper extension for Soundtrack Pro project itself is .stmp. This is the file that can ONLY be opened up in Soundtrack Pro. But you will be creating audio files within the project that you can take to other software programs such as the Flash animation program.)

4.  Create a new audio file and begin digitizing your audio recording

-- Create a new audio file:

File > New > Audio File

-- Save the file as a stereo AIFF or stereo WAV file (either is okay), e.g., "mysoundfile.aif" or "mysoundfile.wav"

-- Open "recording" window:

• Window > Recording
• Check input device is set at "Built-in Audio"
• Check monitor device is set at "Built-in Audio"

-- Use the volume control on the miniDisc recorder to adjust the volume level that will be digitally sampled by the SoundTrack Pro software.

NOTE: when the miniDisc recorder is hooked up to the computer (with the stereo mini cable), the only way you can hear what it is playing back is when you have an Audio File window open (and NOT when you have the sound mixing Audio project window open. You will be using that mixing environment later.)

• Set the recording levels by watching the Recording meter.
• Rule of thumb for avoiding both under-modulated sound (too soft) and over-modulated sound (too loud):
• Get the Input Recording meter (for the SoundTrack Pro software) to be beyond the green area, into the yellow area as much of the time as possble - approximately 6 dB (decibels) - without ever "peaking" into the Red.
• Once you set the level, you should generally leave it alone while digitally sampling your sound. In other words, do not "ride the gain", changing the volume of the input while the digitizing process is going on. The exception might be occasionally if the sound begins to spike (e.g., because of a loud motor, audience applause, etc.)
• Start the miniDisc player at a point in advance of the point where the sound you want to sample begins.
  Press the red record button on the software window (at the bottom of the window).

-- When you are done with sampling the sound, press the "pause" button at the bottom of the software window.

-- Save your Audio file:

File > Save

5.  Process your audio file in the Audio File editing window

File > Open...

-- Select the .aif file that you previously digitized.

-- In the Audio File editing window you can cut, copy, paste as you would in a word processor. You can also highlight areas of the sound to process them by applying effects, time stretching, invert or revert the sound, etc. For example,

• Process > Invert
• Process > FadeIn
• Process > Effects > Reverb/Delay > Tape Delay
• etc.

As with image processing software such as Photoshop, beware of the gratuitous application of filters. On the other hand, do experiment with and become familiar with some of them.

-- Export each of your audio files as an .aif file

File > Export...

-- Once you have saved individual audio files, you are able to Mix selected files together.

5.  Mixing your audio files as combined layers of sound :

--Open the Soundtrack Pro "Browser" window:

Window > Browser

--Drag your audio files from the browser window to the multitrack mixer window

--Click on the "Show Envelopes" button for each of the audio tracks. (Mainly we are interested in the "Volume" envelope. You may also experiment with the "Pan" envelope between left and right stereo channels.)

--Add "envelope points" to change sound level (volume) of a track.

• Essentially "envelope points" are the same thing as "key frames" that are used in Final Cut Pro (and animation programs such as Flash). Envelope points, like key frames for images, simply describe the properties of sound at any particular point in time. The computer "interpolates" the audio transition between any two envelope points.
• To place an envelope point, double-click on the timeline "Volume" band for the audio track where the volume is to transition between loudness and softness.

--If you need to edit your original track further, then double-click on it in the Mixer window and this will open the track in the Audio File editing window

--Save the Soundtrack Pro project file (this is a .stmp file)

File > Save

--Export your sound mix as a separate, new .aif file

• File > Export > Mix...
• The "Bit Depth" should be 16 Bit
• The "Sample Rate" can be either 48 kHz (the default for DVD audio) or at 44.1 kHz (CD quality audio).