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CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Multimedia Building Block : Sound References: T. Vaughan, “Multimedia: Making It Work.

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Presentation on theme: "CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Multimedia Building Block : Sound References: T. Vaughan, “Multimedia: Making It Work."— Presentation transcript:

1 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Multimedia Building Block : Sound References: T. Vaughan, “Multimedia: Making It Work 5 th Edition”, Osborne/McGraw-Hill, 2001 S. McGloughlin, “Multimedia: Concepts and Practice”, Prentice Hall, 2001

2 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Why is sound important in Multimedia? To reinforce message or theme To set the mood To catch the interest of the audience To alert the audience To include narration: effective for training and educational application.

3 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Types of Sound 2 types of sound in multimedia –Music Background Attention grabber etc.. –Speech Narration Instruction etc..

4 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Sound consideration While sound (music or narration) can be very useful, most of the time, they can be irritating as well. –Use appropriate music to reflect the mood or theme. –Give the users choice of turning off/on the sound. –In cases where the content of a page depends on sound (speech), consider providing transcript as the alternative. (for deaf people, non-multimedia pc)

5 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Understanding Sound Sound travels as waves at 750 mph (at sea level) Acoustic – a branch of physics that studies sound. Sound pressure level (loudness or volume) is measured in decibels (dB) Too much sound can have a damaging effects.

6 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Understanding sound Amplitude – is the maximum displacement of the vibrating particles from their undisturbed positions Frequency is measured in cycles-per-second, commonly known as Hearts (Hz)

7 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Multimedia System Sound Most target computers have sounds installed (e.g. default window sounds)

8 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Multimedia System Sound Macintosh and Windows systems have built-in sound recorders.

9 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Type of audio for multimedia application Digital Audio MIDI Audio (Musical Instruments Digital Interface)

10 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Digital Audio - overview Digital audio is a representation of the original sound. Sound digitization is obtained through –Sampling –Quantization –Code-word generation process Digitized sound is called sampled sound.

11 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Digital Audio - overview Digital audio usually uses large storage space Digital audio is less affected by hardware, thus providing consistent playback quality. –Audio track for multimedia project will sound as good in the end as it did in the beginning when it is created. Require less musical talent to record.

12 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Digital Audio - Sampling Every nth fraction of second, a sample of the original sound is captured and stored in digital format (binary digit in bits and bytes) Sampling rate – describes how often the samples are taken. Sampling size – describes the amount of information stored for each sample (bits and bytes)

13 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Digital Audio - Sampling Audio is digitally sampled thousands of times per second. –CD-quality audio is samples 44,100 times per second, thus sampling rate is 44.1 kHz –Other sampling rates commonly used in multimedia are kHz and kHz. Sample size : 8 bits or 16 bits

14 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Digital Audio - Quantization The value of each sample is rounded off to the nearest integer (quantization). If the amplitude is greater than the dynamic range available, clipping of the top and bottom of the wave occurs.

15 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Digital Audio – Quantization & Clipping

16 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Preparing Digital Audio 1. Balance file sizes and quality –Audio resolution determine the accuracy with which a sound can be digitized i.e. how similar the regenerated sound to the original sound. –High quality sound audio requires high sampling rate and size, resulting in large file. –High quality sound requires large storage. –Choose between stereo or mono recording

17 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Preparing Digital Audio Stereo recordings are more lifelike and realistic Mono recording are fine but sound flat. To calculate file size (in byte): Mono: –Sampling rate x duration of recording records x (sampling size / 8) x 1 Stereo: –Sampling rate x duration of recording records x (sampling size / 8) x 2

18 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Preparing Digital Audio 2. Setting proper recording level (loudness) –Watch the meter in the recording device or software carefully to ensure the level of loudness are not too high or too low –Levels that are too high create distortion (sound alteration e.g. unpleasant crackling) –Levels that are too low cause the music to be too soft and overpower by the sound of the recording process itself.

19 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Preparing Digital Audio 3. Editing the recording –Trimming : removing blank space at the beginning or at the end of the recorded audio. –Splice: remove unnecessary noise (touch up) –Assembly: longer recorded audio can be build by cutting and pasting together a few shorter ones. –Convert to another audio format Macintosh : SND and AIF files format Windows : WAV files format

20 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Preparing Digital Audio –Resampling or downsample: resample recorded audio file to a lower audio resolution. e.g. resample / downsample a 16 bit recorded sound to 8 bit. –Fade-in and fade-out: smooth out the very beginning and the very end of the sound file. –Time stretching: alter the length of the recorded sound –Digital Signal Processing (DSP): add special effects to the recorded sound.

21 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Sound Editing Tool Sound Forge is one of the powerful sound editing tool for creating professional soundtracks.

22 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Sound Editing Tool Apple’s QuickTime Player Pro allows you to change sound file formats and compression schemes and do simple cut-and- paste editing

23 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 MIDI Audio - overview MIDI was developed in the 1980s as a standard communications protocol between electronic musical instruments and computer MIDI file is not a digitized sound, it is the shorthand representation of music stored in numeric form (binary) MIDI file contains instructional data (notes, sequences of notes, which instruments etc.) to other devices on how to generate an appropriate sound, it does not have the actual audio data, just the instruction to the instrument or sound card on how to reproduce it.

24 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 MIDI Audio - overview Offer opportunity for developers to compose their own music. MIDI files are much more smaller than digital audio files, thus, –It requires less storage space. –Suitable to be used with web page.

25 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 MIDI audio - overview Inconsistency in playback quality –Playback will only be accurate if the MIDI playback device is identical to the device used for production. Not suitable for spoken dialogue

26 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Preparing MIDI Audio You need: Some musical talent or hire MIDI artists. MIDI instruments (e.g. electronic keyboard) MIDI Sequencer software: –allows you to record, edit and save music generated by MIDI instruments. Computer Sound Hardware or Synthesizer

27 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 MIDI Sequencer Software

28 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Preparing MIDI Audio Sound Synthesizer: –Is needed to translate information generated by the MIDI devices into sound (music). –May also be used to play back the MIDI file. –Typically built into the sound board on PC, but as an add-on board or peripheral for the Macintosh. –For more info, visit

29 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 MIDI Audio System Components MIDI Instrument Synthesizer Computer with MIDI Sound Board MIDI Instrument

30 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Preparing MIDI Audio MIDI can synthesize the sounds of over a hundreds different instruments. How realistic the instruments sound is greatly affected by the hardware it is played on. Each instrument is identified by a numeric General MIDI Instrument Sound code. –Table 9-3, page 218 – 224 in Multimedia: making it work.

31 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Choosing between MIDI and Digital Audio In general, use MIDI data in the following circumstances –You only have small storage space, RAM, CPU processing power or bandwidth. –You have high quality MIDI sound source. –You have complete control over the playback hardware. –You do not need spoken dialogue.

32 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Choosing between MIDI and Digital Audio In general, use digital audio in the following circumstances –You do not have control over the playback hardware –You have the computing resources and bandwidth to handle digital files. –You need spoken dialogue.

33 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Audio File Formats Macintosh : –Audio Interchange File Format (.AIFF) audio –Digitized Sound (.SND) Windows : –Waveform Audio File (.WAV) Both Macintosh and Windows can use MIDIs.

34 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Sound for the World Wide Web Many audio format can now be found online. Sound can be played over the Web in one of two ways. –Downloading: download and save the files to the computer first, then play it. –Streaming: sound is played while it is downloaded from the internet into the computer buffer portion by portion Streaming quality is very sensitive to connection speed and internet traffic.

35 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Adding sound to Multimedia - tips Before adding sound to your multimedia project, decide on: –What kind of sound is needed –When and where to use audio –Decide whether you want to use MIDI or digital –Acquire the source material –Edit the audio to suit your project –Test the sound.

36 CMPD273 Multimedia System Prepared by Nazrita Ibrahim © UNITEN2002 Copyright issues Secure rights for all material you use Look for collections of royalty-free audio


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