itec 715

ITEC 715

Computer Foundations for Instructional Multimedia

Week 7

• E-learning Design Document (EDD) Critiques

• Scripting from your EDD Aiming for an 85% (+/- about 5%) match to between the design specified in the EDD and the script built from it

ITEC 715Recall from Last Week

• In many production environments, IDs write “structured” scripts. Typically, this means scripts are written inside multicolumn script tables, one table per page-type (possibly with a “header” table preceding each “content” table)

ITEC 715Scripting from Your EDD

• Advantages of structured

scripts include: – Structured content has a

defined space for every piece of content and information that is required to build the page, and thus minimizes the chance that the ID will forget to put in something whose absence would slow down the production pipeline

– Structured content can be processed by computer programs to automate some or all of the build process


• You won’t be using a structured script in the class, though

• Instead, simply type your final copy directly into PowerPoint. Lay out your final graphics or place holders for your animations, videos, media controls and other buttons. Place the script for any audio associated with a page in the PowerPoint “Notes” section

• In other words, your script for this class will be a PowerPoint deck


Audio Production for Instructional Multimedia

Module 1: Digital Audio Fundamentals

Sound

Sound is a compression wave in the air. You hear it because your ears convert the changing air densities into signals that your brain interprets as sound.

If you were to graph the compression and rarefaction cycles of a sound wave, you’d end up with something that looks like the picture at the lower right.

Diagram source: Principles of Digital Audio, 2nd Edition by Ken C. Pohlmann (1989)

1 wavelength



Visually Representing a Sound WaveUsually, when drawing a graph of a sound wave, the vertical direction represents amplitude and the horizontal direction represents time.

All sound requires time, so that axis is fairly self explanatory. But amplitude, which is a measure of the relative compaction or rarefaction of the air, is less familiar.

Time (usually in seconds) Am

plitu

de (

usua

lly in

dB

)



Frequency Pitch

High frequency Low frequency

Soft Loud

Amplitude Loudness

Human hearing: 20 Hz – 20,000 Hz

Human hearing: 0 dB – ~120 dB



Module 1: Review

Sound = compression waves in the air

Human Hearing = Frequency range: 20 Hz – 20 KHz; Dynamic range: 0 – 120 dB

Frequency Pitch

Amplitude Loudness/Volume

Sample Rate Highest Freqency

Bit Depth Dynamic Range

Nyquist Theorem Must sample at 2x the sound’s highest frequency


Module 2: Recording with Audacity




MicrophoneNow that you understand the fundamentals of digital audio, you’re ready to start making some digital recordings of your own. To do so, you’ll need two things (at minimum): a microphone and some digital audio recording software. A limited number of mics are available for checkout from SFSU’s Cahill Lab, Burk Hall 319.

If you want to buy one, a relatively decent, inexpensive microphone that will work well for this purpose is the Radio Shack “Hands-Free Tie-Clip Omni-Directional Electret” microphone (part number 33-3013), pictured at right.

Necessary Equipment: A Microphone



Audacity SoftwareYou’ll also need some software to digitize the signal from our microphone. The software you’ll be using is called Audacity. Audacity is free software, available for all three popular home computer operating systems: Linux/Unix, Windows, and Mac OS X.

Audacity is already installed on the computers in this classroom. To get Audacity at home, download it from http://audacity.sourceforge.net/



Making a RecordingYour goal is to record sound so that its loudest portion comes as close as possible to the top and bottom of your work window (the +1.0 and -1.0 lines), but no farther.

Too Soft OKToo Loud

Sound source: “It’s Just A Thing” by Kurt Elling from The Messenger (1997)



ClippingRemember that amplitude values you can measure are directly related to how many bits you’ve devote to each measurement. If your sound level is so high that you run out of bits trying to measure it, you get clipping.

Waveforms with clipped peaks sound distorted. Generally, this is something you want to avoid.

Clipping

Sound source: “It’s Just A Thing” by Kurt Elling from The Messenger (1997)



Room Tone (cont.)Rooms of differing sizes and differing configurations have different-sounding room tones, but since you can’t have sound without air (remember: sound is density changes in air), room tone will always be present when you make recordings indoors.

signalnoise

noise floorTrue silence



Making a Recording1. Launch Audacity2. Choose File -> Preferences3. Click on the Quality tab4. Select your sample rate (you can leave

everything else at the default values)5. Push the big red “Record” button6. Set your levels by speaking into the

microphone and then seeing how “hot” your signal is

7. When you’re done recording, press the yellow “Stop” button

Go to beginning

Play

Record

Pause

Stop

Go to end



Editing a Recording – Useful Audacity Tools

1. Selection Tool: Use this to select subsections of your sound. Once selected, these portions of your sound can be deleted, or effects can be applied.

2a. Magnify Tool: Use this to zoom in or (with the Shift key held down) to zoom out.

2b. Magnify/Unmagnify Tools: You can also zoom in or out using these tools.



Saving a Recording1. Save the Audacity Project file first by

choosing File -> Save Project As…

2. Finally, export the WAV file by choosing File -> Export as WAV

Audacity, Part 2

This Week



Normalizing and Digital Noise Reduction1. Select the entire wave (cmd-a)2. Choose Effect -> Amplify3. Accept the defaults and hit OK to normalize

the sound (peak normalization)4. Using the Selection Tool, select a passage

that is supposed to be silent5. Choose Effect -> Noise Removal… and

press the Get Noise Profile button6. Select the entire wave (cmd-a)7. Choose Effect -> Noise Removal…8. Adjust the slider (usually toward “less”) and

use Preview until it sounds good. Then press the Noise Removal button.

Selection Tool

Noise R

emoval


Module 3: Delivering Audio to Flash and the Web

Some Background Info About the Mp3 Format



“Lossless” vs. “Lossy” in Audio EncodingWAV files are generally too big to deliver in an online instructional multimedia product. That’s why you will often want to compress your WAV original into a smaller mp3.

How does the mp3 encoding process manage to squash the size of the sound down so much?

The answer is: it throws some of the sound information away!

44.1 KHz / 16 bit mono WAV file

32 kbps mono mp3 file

5,169 KB 235 KB

The mp3 file is much smaller because it throws away some audio information.

Relative sizes of a 1 minute sound



“Lossless” vs. “Lossy” in Audio EncodingThere are two kinds of data compression: “lossless” and “lossy”.

Compression schemes like Stuffit and Zip are lossless. This means that when you uncompress a file that has been “Zipped”, you get back a file that is identical to the file you originally compressed.

But with mp3s, this is not true. Some information is lost during mp3 compression and cannot be recovered during decompression.

Lossless Compression Lossy Compression

Compress (Unix) Mp3 (audio)

Gzip (Unix) ATRAC (audio)

Stuffit (Macintosh) MPEG-2 (video)

Zip (Windows) MPEG-4 (video)

Popular compression algorithms, classified as lossless or lossy. Lossless algorithms recover an identical copy of the original file. Lossy algorithms do not.



“Lossless” vs. “Lossy” in Audio EncodingThe technical term for algorithms which have both an encoder and decoder part is codec (a somewhat bizarre contraction of “encode / decode”).

Since mp3 is a lossy codec, you do NOT want to convert your sound into the mp3 format until you are completely done editing it! If you edit an mp3 and want to save it back out as an mp3, you’ll have to run it through the mp3 encoder again, and every time you do that, you will degrade the quality of your sound.

Original 44.1 KHz / 16 bit stereo WAV file

48 kbps stereo mp3 file – 1st Generation

48 kbps stereo mp3 file – 10th Generation



Exporting Mp3s Out of Audacity



Exporting Mp3s from Audacity1. Choose File -> Preferences to pop up the

preferences dialog, then click on the File Formats tab.

2. Choose a Bit Rate – lower bit rates result in smaller files but worse sound quality.

3. Hit OK to save your settings.4. Choose File -> Export as Mp3… 5. Give the mp3 file a name. Hit Save, then

on the following dialog box, just accept the defaults and hit OK.

Creating Royalty-FreeMusic with GarageBand

Background Music

• Other sources of royalty-free background music include:• Additional GarageBand “Jam Packs”:

http://www.apple.com/ilife/garageband/jampacks/

• Royalty-free library music (do an Internet search on “royalty free music”)

• Output of other “loop editors” such as Soundtrack (Apple), Sony’s Acid (PC), and Adobe’s Audition (PC)

ITEC 715GarageBand



Audacity, Part 3: Mixing Voice-Over Narration

with Background Music

Mixing Voice and Music



Voice-Over Mixing1. Write a script and rehearse it before

recording!2. Launch Audacity3. Record and edit your voice track4. Save your work!5. With the completed voice track still

loaded, choose Project -> Import Audio to import your music track

6. Next, split your stereo music track into two mono tracks by using the drop-down menu by the track name and choosing Split Stereo Track



Voice-Over Mixing (cont.)7. Next convert each of the 2 split music

tracks into a “mono” track, again using the drop-down menu by the track name.

8. Select the two music tracks by clicking on track control area (use shift-click to select the second track).

9. Now mix these two music tracks together into a single mono track by choosing Project -> Quick Mix.

NOTE: If we were mixing two tracks that weren’t already part of a clean stereo mix, we’d want to make sure there was no clipping in the newly combined mono track.



Voice-Over Mixing (cont.)11. Use the Time Shift Tool to move the

tracks forward or backward in time.12. You can also use the Selection Tool

to highlight sections of the music track you don’t want – such as introductory passages from the beginning – and delete them using Edit -> Cut or the equivalent keyboard shortcut: cmd-x

13. While testing out ideas, you can adjust the relative levels of each track using the volume slider on the track’s left

Track Volume

Time Shift Tool



Voice-Over Mixing (cont.)14. With the voice and music track lined

up as you want them, you’re ready to start adjusting the relative volumes of the tracks by using the Envelope Tool

15. Click with the Envelope Tool to create new pivot points for the envelope curve. Drag the line to adjust volumes up or down as desired.

16. Let the music run for 5-10 seconds past the end of the narration. Use the selection tool to create a fade-out (Effects -> Fade Out) over the last 5-10 seconds. Fade the same section out twice to get a smoother curve.



Voice-Over Mixing (cont.)

17. Select everything after the fade-out on the music track and delete it

18. Save the Project file at this stage with a name ending in “-u”, then save it again with the same name, but ending in “-m” instead of “-u”. That way we’ll save our “unmixed” and “mixed” versions. If we discover problems later, we can remix without having to do all Time Shift and Envelope work again.



Voice-Over Mixing (cont.)

20. Select both tracks, then choose Project -> Quick Mix to mix the VO and music tracks into a single monophonic track.

21. Listen to the track to make sure that combining these tracks didn’t cause any clipping. If it did, undo the Quick Mix, take each track down 3 dB, and do the Mix again. You should re-normalize this final track as well.

22. Save the Project file at this stage over the file name ending in “-m”.

23. Choose File -> Export as WAV to save the WAV file.

• Continue scripting your course!• Find or create some music for your splash page• Mix that music with a spoken welcome message. In this mix,

the final file should begin with music only, at full volume. The music should then fade down to a softer volume when the voice comes in and while it is speaking. As the voice finishes, the music should swell up to full volume again, hold for a few seconds, and then fade out.

• Turn in your audio as both the Audacity Project file and as a 44.1 KHz, 16 bit stereo WAV or AIFF file

• Download and read the ITEC715-Week08.ppt slides

ITEC 715For Next Week

itec 715

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