3. You have been assigned to design and
produce the audio portions of a multimedia project. The program will be
delivered on a CD-ROM, and video clips will take up most of the CD. You have
only 50MB of storage space to store 20 one-minute clips of speech, 10 songs
averaging three minutes long, and a background sound loop. What sampling rates
and depths should you use for the speech, for the music, and for the background
sound? Why?
I would decide to use the mp3 format for my
entire audio file in the video clip as it has been compressed while able to
maintain the sound quality. For the speech part, I would like to use 96 kbps
bit rate, for the music and use 128kbps bit rate as the sound quality is near
the CD quality. Finally, for the background loop song, I would choose 128kbps
bit rate!
Speech (20)
60 seconds * 96 kbps = 5760 kilobits of
data
5760/8 = 720kb (0.72mb)
0.72 * 20 = 14.4mb
Music (10)
180 seconds * 128kbps = 23040kilobits of
data
23040/8 = 2880kb (2.88mb)
2.88 * 10 = 28.8mb
Background song
300 seconds * 128kps = 38400 kilobits of
data
38400/8 = 4800kb (4.8mb)
Total: 14.4+28.8+4.8 = 48mb
5. List the steps you would go through to
record, edit and process a set of sound files for inclusion on a web site. How
would you digitally process the files to ensure they are consistent, have
minimum file size, and sound their best?
(a)
Steps
Step1: The file size (in bytes) of a
digital recording is sampling rate * duration of recording in seconds * (bit
resolution/8) * number of tracks (1 for mono, 2 for stereo).
Step2: Consumer-grade audio compact discs
are recorded in stereo at sampling rate of 44.1 kHz and a 16-bit resolution.
Other sampling rates include 22.05 and 11 kHz, at either 16 or bites.
Step3: Digital audio is not device
dependent, and sounds the same every time it is played. For this reason digital
audio is used far more frequently than MIDI data for multimedia sound tracks.
You can digitize sounds from any source, live or prerecorded.
Step4: When recording (digitizing) audio,
it’s important to keep the recording level near the maximum without going over
it.
Step5: Important steps in digital sound
editing include removing blank space from the start and end of a recording and
normalizing the sound to bring all clips to approximately the same level.
Step6: The native sound file formats for
most Macintosh sound editing software are the SND and AIF formats, and most
authoring systems will read these formats. In Windows, the native sound file
format for most editing software is a WAV file.
Step7: Many audio editors provide tools
such as re-sampling fade-ins and –outs, equalization, time stretching, various
digital signal processing effects, and reversing sounds.
Step8: The value of each sample is rounded
off to the nearest integer (quantification), and the preparation and
programming required for creating digital audio do not demand knowledge of
music theory.
(b)
Determine the best & minimize files:
MIDI scores require sequencer software and
a sound synthesizer. The General MIDI format standardizes a set of MIDI
instruments, ensuring that the MIDI sequence is played correctly. Streaming
files begin playing when part of the file has been buffered into the computer’s
memory and are dependent upon connection speed. Adobe’s Flash provides powerful
tools for integrating and streaming sounds, including the MP3 format. Apples’
QuickTime is a file format that, among other capabilities, enables digital
audio to be interleaved with video information.
