WEEK 5 Blogging Question 6: Page 138 Q 3&Q 5

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.