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Chapter10 Chapter10 Document Transcript

  • Chapter 10 Audio Formats And Software OBJECTIVES At the end of this chapter, you should be able to: 1. name a few main audio file formats used in multimedia; 2. INTRODUCTION in the market; and know a few audio software 3. learn how to process sound with Sound Forge software. INTRODUCTIONIn this chapter, you will be introduced to some types of audio file formatsnormally found in multimedia such as WAV, MP3, AIFF and MIDI, and theirspecial features. You will also identify the audio file sources and copyright issues.Besides knowing several audio software that are available in the market, you willalso learn some basic techniques on how to process sound with the use of theSound Forge software at the end of this chapter.
  • CHAPTER 10 AUDIO FORMATS AND SOFTWARE 17510.1 AUDIO FILE FORMATSWith the emergence of digital audio, sound or music can be recorded in a varietyof formats; among them are the AIFF, AU, MIDI, MP3, SWF and WAV formats.Most of these audio file formats involve compressing the audio files. Audio filecompression is needed to save storage space. Audio that has been compressedcan be replayed with just a low percentage drop in its quality. AdaptiveDifferential Pulse Code Modulation (ADPCM) is one of the main methods ofaudio compression.Now, the QuickTimes movie (.mov) standard, is often used to store audio files asthis type of file can be used in most computer platforms including PC computersand Macintosh computers.As for the use of audio on the Internet, Real Audio, Real Media and MP3 can beused in view of the fact that, their file sizes are smaller compared to other audioformats.In the future, it is highly possible that more new audio formats will emerge,where you will be able to listen to audio with not only small file sizes but are alsoof high quality. Following are explanation of the common types of digital audioformats. Figure 10.1: Digital audio format10.1.1 AIFFAIFF format (Audio Interchange File Format) is one of the common formats usedto store and send sound samples. This format was first developed by Apple
  • 176 UNIT 3 MULTIMEDIA COMPONENTS II: AUDIO & VIDEOcomputers and is the standard format for Macintosh computers. Now, it can alsobe used by computers with Windows operating system.AIFF format is usually not able to do data compression; therefore, AIFF files areusually bigger than other formats. Nevertheless, there is another format that cansupport data compression and that is the AlF-compressed (AlFF-CorAIFC)format.AIFF format is widely used in professional audio recording systems and digitalmultimedia applications that use Macromedia Director and Adobe Premieresoftware. Both software allow the importing and exporting of the AIFF files. Onething that you need to know is that an AIFF audio file is of high quality when ituses high resolution. However, this causes its file size to become very big. Forexample, a 30 second long 16 bit stereo will have a file size as big as 5.4MB.10.1.2 MP3This audio format is extremely popular now and it is often used to record a largenumber of songs and music onto compact discs. MP3 means MPEG audio layerIII and it was created by a German company, Fraunhofer Gesellschaft in 1989.One of the main reasons why MP3 is so popular and favoured by music lovers isits extraordinary compression ratio of 10:1 for audio files such as WAV. The ratioof 10:1 means that if the WAV file is converted to MP3 format, its new size is only10% of the original WAV file size, but its audio quality remains the same. Besidesthat, MP3 format also allows various sampling rates and bit rates, whereby itgives users more authority to control the file size and quality.For MP3, the ordinary sampling rate is 44.1 kHz and its bit rate is 128 kbps. It isdifficult to distinguish the MP3 music quality from the quality of the music thathas not undergone the compression process. You can play MP3 songs or music byusing a Winamp player which was created by Nullsoft. One of the mainadvantages of MP3 is that it is capable of storing additional textual informationsuch as the subject, artistÊs name and comments. All of these can be shown on theWinamp player.10.1.3 AUAU audio format was specially created to be used on the Sun Microsystemsworkstation. It is a 16 bit audio format that is compressed and used fordistribution via the Internet. AU audio format is less popular compared to theWAV format.
  • CHAPTER 10 AUDIO FORMATS AND SOFTWARE 177 THINK You can download free Winamp player from the Internet. Use the browser to obtain this software. List the address. What is your opinion about this music player? Does it give you the effect as mentioned above?10.1.4 MIDIMIDI format ((Musical Instruments Digital Interface) was first used in 1980, as aneffective method of music representation that could be used in variousapplications. In fact, MIDI is not an audio format. It is more of an interface toproduce audio. The audio produced would then be kept in MIDI format.MIDI is a standard language used for communications between musicalinstruments and computers. This means a musician can attach the electronic key,guitar and other MIDI tools to audio synthesiser connected to the personalcomputer. Users can compose their own music which would then be convertedinto digital sound. This means a composer can use the MIDI keyboard to recordnotes and then can convert this information easily into the computer.A sequence of MIDI that has been compressed makes it very useful forapplications where space is an issue. For example, songs for video games, musicfor websites and background music are applications of good MIDI formats. MIDIhas many advantages compared to other digital audio. Among the advantagesare; MIDI tracks requires less bandwidth and processing power compared toMP3 files. For example, when you download a MP3 track using a modem, youmay be disappointed because you need half an hour just to download a singlemusic track.On the other hand, if you download a MIDI file, you can obtain the file in lessthan a minute even though you use a slow speed modem. MIDI sequence ortracks are much smaller than any digital audio files. One MP3 track normallyuses only 1MB of disk space for a minute of music, but a MIDI track only requires40KB of disk space which is 95% smaller than a MP3 and its quality is notcompromised!
  • 178 UNIT 3 MULTIMEDIA COMPONENTS II: AUDIO & VIDEO10.1.5 WAVA WAV file is the main and popular audio format in the Microsoft Windowsoperating system environment. It is unlike MPEG or compressed format. It storesamples without the need of pre- processing. The format of this file is similar tothe AIFF format.A WAV files is usually huge. Its file size is dependent on the length of the audiobeing recorded and the sampling rate used for recording. It is later replayed at acompatible rate. You can record and replay a WAV file with the Sound Recorderthat is inbuilt in the Microsoft Windows environment.The following passage explains the differences between MIDI files and digitalaudio. MIDI versus Digital AudioMIDI (Musical Instrument Digital Interface) is a communications standarddeveloped in the early 1980s for electronic musical instruments and computers. Itallows music and sound synthesisers from different manufacturers tocommunicate with each other by sending messages along cables connected to thedevices. MIDI provides a protocol for passing detailed descriptions of a musicalscore, such as the notes, sequences of notes, and what instrument will play thesenotes. But MIDI data is not digitised sound; it is a shorthand representation ofmusic stored in numeric form. Digital audio is a recording, MIDI is a score · thefirst depends on the capabilities of your sound system, the other on the quality ofyour musical instruments and the capabilities of your sound system.A MIDI file is a list of time stamped commands that are recordings of musicalactions (the pressing down of a piano key or a sustain pedal, for example, or themovement of a control wheel or slider) that, when sent to a MIDI playbackdevice, results in sound. A concise MIDI message can cause a complex sound orsequence of sounds to play on an instrument or synthesiser; so MIDI files tend tobe significantly smaller (per second of sound delivered to the user) thanequivalent digitised waveform files.In contrast to MIDI data, digital audio data is the actual representation of asound, stored in the form of thousands of individual numbers (called samples).The digital data represents the instantaneous amplitude (or loudness) of a soundat discrete slices of time. Because it is not device dependent, digital audio soundsthe same every time it is played. But that consistency comes at a price; large datastorage files. Digital sound is used for music CDs.
  • CHAPTER 10 AUDIO FORMATS AND SOFTWARE 179MIDI data is to digital audio data what vector or drawn graphics are tobitmapped graphics. That is, MIDI data is device dependent; digital data is not.Just as the appearance of vector graphics differs depending on the printer deviceor display screen, the sounds produced by MIDI music files depend on theparticular MIDI device used for playback. Similarly, a roll of perforated playerpiano score played on a concert grand would sound different than if played on ahonky tonk piano. Digital data, on the other hand, produces sounds that aremore or less identical regardless of the playback system. The MIDI standard islike PostScript, letting instruments communicate in a well understood language.(Reference: Multimedia Making It Work, Tay Vaughn, 2001: 205 - 206). Exercise 10.1 After reading the excerpt above, can you state TWO advantages and TWO disadvantages of MIDI compared to digital audio? Visit its web site at http://www.musitek.com to see the scanner software that can read notes or musical scores and convert them into MIDI files.10.2 SOURCE OF AUDIO FILESAlmost all multimedia computers today are equipped with sound cards andspeakers; this indicates how important audio is as a media, in our daily lives.If you are observant, you will notice that when you open or close an applicationon a Windows operating system, your action is accompanied with a sound. Thissound can be changed according to an individualÊs preference at any time.Sounds such as this are stored in a file and its source can be obtained from pre-packages, purchases or borrowings, and from your own inventions.
  • 180 UNIT 3 MULTIMEDIA COMPONENTS II: AUDIO & VIDEO10.2.1 PrePackage Figure 10.2: Sound FileSome sound files can be obtained from the computerÊs operating system or fromprograms that already exist in your computer. Figure 10.3 below shows the soundfile that is in Microsoft Office. These sound files can produce special effects suchas the sound of doors opening; car braking and others.10.2.2 Buying and BorrowingOther than the pre-packages built into an operating system or applicationsoftware, sound files can also be bought from companies that specialise inproduction of sound clips. In addition, the Internet is the right place to purchasesound clips. Sometimes you can also get it free by downloading it from theInternet.These file resources can be very useful for background sounds, sound withspecial effects and also for historical events, such as speeches or conversations ofthe Prime Minister.10.2.3 Own InventionSound file can also be produced through your own invention. Sound clips mightbe created easily by using specific program together with a microphone. One ofthe factors that must be considered when creating a sound file is the quality of thesound to be generated. If you want to include sound into a PowerPointpresentation, you can use a medium quality sound.On the other hand, if you aim to produce a commercial of high quality, youshould consider using a recording studio equipped with instruments such asDAT (Digital Audio Tape) that can record digital sound. Additionally, sound filescan also be generated by using equipment such as an audio synthesiser connected
  • CHAPTER 10 AUDIO FORMATS AND SOFTWARE 181to the computer so that the sound can be recorded in MIDI (Musical InstrumentDigital Interface) format.Before we proceed to the next topic, make sure that, when obtaining these sourcesof audio files, you did not infringe or violate the CopyrightÊs Act, which is acritical issue concerning music. To be safe, always make sure that the music youuse is royalty free. There are several new products such as ACID from Sonic Foundry that allows users to produce sound which is not only professional, but also unique. Visit its web website at www.sonicfoundry.com Exercise 10.2 As a multimedia developer you should make sure that the work you produce will not be copied by other people. The CopyrightÊs Act (Amendment) 1997 was created to solve this problem, give brief information about this Act. 10.3 AUDIO SOFTWAREJust like video, attention should also be paid to audio in a multimedia system.Audio management such as recording and editing is very important to generategood multimedia products especially video clips where the audio is synchronisedwith the video display.Just like video, audio requires specific software for recording purposes or for theaudio production. The Microsoft Windows operating system provides audiorecording facility through its software called Sound Recorder (refer Figure 10.3)
  • 182 UNIT 3 MULTIMEDIA COMPONENTS II: AUDIO & VIDEO Figure 10.3: Sound recorderFor the purpose of producing better audio with attractive special effects,sophisticated audio software are required such as Sound Forge and SoundEdit 16.The following are discussions on major audio software.10.3.1 Sound ForgeSound Forge is professional audio editing software for Windows. It includes anaudio processing set, equipment and special effects to manipulate audio. SoundForge is very useful as it works well with the WindowsÊ compatible sound cardsto create, edit and record audio files. This user friendly interface software enablesthe process of editing to be done quickly and easily.Sound Forge has special features that make it so popular. Among the specialfeatures are; Has internal support to record video and CD. It can store a lot of video and audio file formats that include WAV, AVI and MP3; Has excellent editing features such as cut, mute, reverse, trim, normalise, and others; Has an amazing effects. This includes 20 types of DirectX audio plug-ins that can be used for microphone modelling. Other effects such as, chorus, distortion and others; Support many file formats such as WAV, RealAudio, and MP3; and It is easy to use. It uses the drag and drop operation in a user friendly interface.
  • CHAPTER 10 AUDIO FORMATS AND SOFTWARE 18310.3.2 SoundEdit 16This software has features that are almost similar to Sound Forge. It can doediting for more than 10 audio formats. Besides that, it also has Mixer, CD AudioCapture and others. Nevertheless, it only operates under the MacOs (Macintosh)operating system.The advantages of SoundEdit 16 are that it can import and export AU file formatsfrom the Internet. SoundEdit 16 also supports compression such as algorithmcompression 4:1 for a 16-bit voice. Other than that, you can also import CD tracksdirectly into SoundEdit 16; then, edit, process and give it the desired effect.With these features, audio recording and editing has become a process that can bedone by both the professionals and the common users.10.4 PROCESSING SOUND WITH SOUND FORGESound can be processed through software applications that are available in themarket. The most popular software to process audio is the Sound Forge. It is easyto use and understand regardless of whether you are a beginner, or have alreadymastered it. There are several important steps in processing digital audio whichare:(a) The process of opening and playing sound files;(b) The process of recording and copying sound files;(c) The process of editing sound files;(d) The mixing process; and(e) The process of compressing for Internet use.10.4.1 The Process of Opening and Playing Sound FilesOpening and playing sound files is a very basic and easy process with SoundForge. You can open any number of sound files that you want, simultaneously onthe screen.The first step is to click the File button, then click the Open button as shown inFigure 10.4. If you want to close a file that is not needed, you can click on File andthen click Close.After you have clicked on Open, a window, as shown in Figure 10.5, will appear.You should choose the required sound file and then click the Open button. Afteropening the file, you can listen to the entire sound file by just clicking the PlayAllbutton that is available on the Transport Toolbar as shown in Figure 10.6.
  • 184 UNIT 3 MULTIMEDIA COMPONENTS II: AUDIO & VIDEOFigure 10.4: Opening a Sound File Figure 10.5: Choosing and Opening a Sound FileMeanwhile, you can play the sound file at any starting point by just clicking atdifferent locations using the mouse, and then click on the Play button. Then, youwould be able to listen to the sounds, starting from the cursor position till the endof the file.You can also play part of the sound data by choosing the waveform like indicatedon Figure 10.7. You can use the mouse to make the choice. You only need to clickthe left button of the mouse and drag it to the right side; the black shaded arearepresents the chosen section. When you click on the Play button, you will onlyhear the chosen sound. Figure 10.6: Transport Toolbar
  • CHAPTER 10 AUDIO FORMATS AND SOFTWARE 185 Figure 10.7: Waveform10.4.2 The Process of Recording and Copying Sound FilesThe process of recording and copying sound files is very important. This is thefirst step in producing a new sound file.First, you need to insert the compact disc with the sound file sample (.wav), andthen click on the Start button in the Windows system. Subsequently, chooseAccessories -> Multimedia -> CD Player. A CD player window will be displayedas shown in Figure10.8. Figure 10.8: CD player windowAfter this window emerges, you can open the Sound Forge window and thenclick on File -> New. After that, a new window, as shown by Figure 10.9, would
  • 186 UNIT 3 MULTIMEDIA COMPONENTS II: AUDIO & VIDEOappear. Here, you should ensure that the sampling rate is 44,100Hz, the samplesize is 16-bit and the channel is stereo, and then press the OK button. Figure 10.9: New file windowA new Sound Forge program window will be displayed. Here, you mustcoordinate the Sound Forge program window with the CD player window so thatboth the windows can be seen, as shown in Figure 10.10. This is because you needto use both the windows to record sounds. Figure 10.10: Sound Forge Programme Window (left) and CD Player (right)When you are ready to begin recording, you only need to click on the Recordbutton (the button with a red circle) which is on the Transport Toolbar. After that,a record window will emerge as shown in Figure 10.11. Then, you should changethe mode to Automatic retake, input format to Time, and finally mark theMonitor checkbox. When all this has been done, you can click on the Preparebutton. You will see the word, ÂPreparedÊ flashing on a small green coloured box.
  • CHAPTER 10 AUDIO FORMATS AND SOFTWARE 187 Figure 10.11: Record WindowWhen all steps are done, you can click on the Record button, and then click on thePlay button which is on the CD player window. After 20 seconds, clik on the Stopbutton to stop the recording and also click on the Stop button of the CD player.Finally, close the record window (Figure 10.11) because the sounds have beensuccessfully recorded10.4.3 The Process of Editing Sound FilesThe editing process enables you to do editing or cut MP3 track that you like. Thefirst step is to click on File -> Open. An Open window will be displayed. Thenyou can choose the required sound file by clicking on the Open button where amain Sound Forge window (Figure 10.12) will be displayed. Figure 10.12: Main Sound Forge window
  • 188 UNIT 3 MULTIMEDIA COMPONENTS II: AUDIO & VIDEOYou can play this sound file by just clicking on the Play button to hear the overallsound file, but if you wish to cut out a section (say area A1) of the sound file, youonly need to use the mouse to click and drop until you reach the section you wishto discard (Figure 10.13). Figure 10.13: Sound section (shaded) that you wish to discard.After that, click on Edit ·> Delete to discard the selected section. Later, you canstore the sound with a new file name that you like by clicking File -> Save As.When you click the Save button, a dialogue box, as shown in Figure 10.14, will bedisplayed and then, you need to click the No button. Now you can listen to thesong that you have edited. Figure 10.14: Dialogue box10.4.4 The Mixing ProcessThe mixing process is a process of combining two different sounds. This processis started by opening a sound file by clicking File ·> Open. Then, choose thesound file, for example, voiceover.wav which you wish to edit. After choosing thesound file, you can click on the Open button and a waveform can be seen asshown in Figure 10.15.
  • CHAPTER 10 AUDIO FORMATS AND SOFTWARE 189 Figure 10.15: Waveform for the sound file Voiceover.WavYou can then choose all the waveform by clicking Edit -> Select All. Then, clickEdit ·> Copy. After that, you can open another sound file; letÊs say the soundfile, mix.wav. A waveform will be displayed on the screen as shown in Figure10.16. Now, you may determine the areas that you wished to combine. You canclick on any place of the waveform, for example area B2, as shown in the circledarea in Figure 10.16. Figure 10.16: Waveform for Mix.wav fileThen, you can click Edit -> Paste Special -> Mix. A window as shown in Figure10.17 will be displayed. In the Name box, you should choose Voice Over Mix, andthen click the OK button. After that, you can keep the file by clicking on File ->Save. When these steps are completed, you can then hear the song.
  • 190 UNIT 3 MULTIMEDIA COMPONENTS II: AUDIO & VIDEO Figure 10.17: Mix window10.4.5 Compression Process for Internet UseSometimes we wish to export a sound file via the Internet, but the huge file sizecauses the sending process to become slow. As such, this software is able tocompress the required sound file. If you want to compress a sound file, in the firstplace, you should open the file by clicking File -> Open, and choose the requiredsound file, and then click Open. After that, you need to click on File -> Properties.A Properties window will be displayed as shown in Figure 10.18. Figure 10.18: Properties window
  • CHAPTER 10 AUDIO FORMATS AND SOFTWARE 191Now, you can click on Process -> Resample. A Resample window will bedisplayed as shown in Figure 10.19. At the Name window, choose 22,050Hz withanti-alias filter, and then click the OK button. Figure 10.19: Resample windowNow, the compression process has been successfully executed. The selectedsound file has been converted into the AU format. Now, you can click, File->Save As, and a Save As window will appear. Through this window, go to Save astype and choose, NeXT/ Sun(Java) File (*.au, *.snd) from the drop down list. Alsogo to Format and choose, G.711 u-Law, and then only click, Save.After clicking Save, a dialogue box will be displayed as shown in Figure 10.20,and you can then click, Yes. Finally, you can start this file or close it. Figure 10.20: Dialogue box YOUR IDEA Try editing a sound file using Sound Forge software without referring to this book. What are your opinions on this software?
  • 192 UNIT 3 MULTIMEDIA COMPONENTS II: AUDIO & VIDEO Exercise 10.3 1. The _____________________ process is the first step in producing a sound file, whereas the ____________________ process is the process of combining two different kinds of sound. 2. State the steps required to open and play a sound file in Sound Forge. 3. Name THREE types of audio file formats that are currently available. SUMMARYTo integrate the audio element into a multimedia project, you do not require adeep knowledge of sound. However, you should equip yourself with the basicknowledge as to how sound is produced, know the audio file formats and learnhow to record and edit sounds on the computer. Thus, this chapter has presentedto you, several file formats used to record digital audio. You also know thedifferences between digital audio and MIDI. At the end of this chapter, you alsolearned several basic techniques on how to generate an audio file with the use ofthe Sound Forge software.