chapter10

INTRODUCTION

INTRODUCTIONIn this chapter, you will be introduced to some types of audio file formats normally found in multimedia such as WAV, MP3, AIFF and MIDI, and their special features. You will also identify the audio file sources and copyright issues. Besides knowing several audio software that are available in the market, you will also learn some basic techniques on how to process sound with the use of the Sound Forge software at the end of this chapter.

CChhaapptteerr 1100 AudioFormatsAndSoftware

At the end of this chapter, you should be able to:

1. name a few main audio file formats used in multimedia;

2. know a few audio software in the market; and

3. learn how to process sound with Sound Forge software.

OBJECTIVES

CHAPTER 10 AUDIO FORMATS AND SOFTWARE 175

10.1 AUDIO FILE FORMATS With the emergence of digital audio, sound or music can be recorded in a variety of 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 file compression is needed to save storage space. Audio that has been compressed can be replayed with just a low percentage drop in its quality. Adaptive Differential Pulse Code Modulation (ADPCM) is one of the main methods of audio compression.

Now, the QuickTime's movie (.mov) standard, is often used to store audio files as this type of file can be used in most computer platforms including PC computers and Macintosh computers.

As for the use of audio on the Internet, Real Audio, Real Media and MP3 can be used in view of the fact that, their file sizes are smaller compared to other audio formats.

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 also of high quality. Following are explanation of the common types of digital audio formats.

10.1.1 AIFF

AIFF format (Audio Interchange File Format) is one of the common formats used to store and send sound samples. This format was first developed by Apple

Figure 10.1: Digital audio format

UNIT 3 MULTIMEDIA COMPONENTS II: AUDIO & VIDEO176

computers and is the standard format for Macintosh computers. Now, it can also be used by computers with Windows operating system.

AIFF format is usually not able to do data compression; therefore, AIFF files are usually bigger than other formats. Nevertheless, there is another format that can support data compression and that is the AlF-compressed (AlFF-CorAIFC) format.

AIFF format is widely used in professional audio recording systems and digital multimedia applications that use Macromedia Director and Adobe Premiere software. Both software allow the importing and exporting of the AIFF files. One thing that you need to know is that an AIFF audio file is of high quality when it uses high resolution. However, this causes its file size to become very big. For example, a 30 second long 16 bit stereo will have a file size as big as 5.4MB.

10.1.2 MP3

This audio format is extremely popular now and it is often used to record a large number of songs and music onto compact discs. MP3 means MPEG audio layer III 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 is its extraordinary compression ratio of 10:1 for audio files such as WAV. The ratio of 10:1 means that if the WAV file is converted to MP3 format, its new size is only 10% of the original WAV file size, but its audio quality remains the same. Besides that, MP3 format also allows various sampling rates and bit rates, whereby it gives 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 is difficult to distinguish the MP3 music quality from the quality of the music that has not undergone the compression process. You can play MP3 songs or music by using a Winamp player which was created by Nullsoft. One of the main advantages of MP3 is that it is capable of storing additional textual information such as the subject, artistÊs name and comments. All of these can be shown on the Winamp player.

10.1.3 AU

AU audio format was specially created to be used on the Sun Microsystems workstation. It is a 16 bit audio format that is compressed and used for distribution via the Internet. AU audio format is less popular compared to the WAV format.


10.1.4 MIDI

MIDI format ((Musical Instruments Digital Interface) was first used in 1980, as an effective method of music representation that could be used in various applications. In fact, MIDI is not an audio format. It is more of an interface to produce audio. The audio produced would then be kept in MIDI format.

MIDI is a standard language used for communications between musical instruments and computers. This means a musician can attach the electronic key, guitar and other MIDI tools to audio synthesiser connected to the personal computer. Users can compose their own music which would then be converted into digital sound. This means a composer can use the MIDI keyboard to record notes and then can convert this information easily into the computer.

A sequence of MIDI that has been compressed makes it very useful for applications where space is an issue. For example, songs for video games, music for websites and background music are applications of good MIDI formats. MIDI has many advantages compared to other digital audio. Among the advantages are; MIDI tracks requires less bandwidth and processing power compared to MP3 files. For example, when you download a MP3 track using a modem, you may be disappointed because you need half an hour just to download a single music track.

On the other hand, if you download a MIDI file, you can obtain the file in less than a minute even though you use a slow speed modem. MIDI sequence or tracks are much smaller than any digital audio files. One MP3 track normally uses only 1MB of disk space for a minute of music, but a MIDI track only requires 40KB of disk space which is 95% smaller than a MP3 and its quality is not compromised!

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?

THINK


10.1.5 WAV

A WAV file is the main and popular audio format in the Microsoft Windows operating system environment. It is unlike MPEG or compressed format. It store samples without the need of pre- processing. The format of this file is similar to the AIFF format.

A WAV files is usually huge. Its file size is dependent on the length of the audio being recorded and the sampling rate used for recording. It is later replayed at a compatible rate. You can record and replay a WAV file with the Sound Recorder that is inbuilt in the Microsoft Windows environment.

The following passage explains the differences between MIDI files and digital audio.

MIDI versus Digital Audio

MIDI (Musical Instrument Digital Interface) is a communications standard developed in the early 1980s for electronic musical instruments and computers. It allows music and sound synthesisers from different manufacturers to communicate with each other by sending messages along cables connected to the devices. MIDI provides a protocol for passing detailed descriptions of a musical score, such as the notes, sequences of notes, and what instrument will play these notes. But MIDI data is not digitised sound; it is a shorthand representation of music stored in numeric form. Digital audio is a recording, MIDI is a score · the first depends on the capabilities of your sound system, the other on the quality of your musical instruments and the capabilities of your sound system.

A MIDI file is a list of time stamped commands that are recordings of musical actions (the pressing down of a piano key or a sustain pedal, for example, or the movement of a control wheel or slider) that, when sent to a MIDI playback device, results in sound. A concise MIDI message can cause a complex sound or sequence of sounds to play on an instrument or synthesiser; so MIDI files tend to be significantly smaller (per second of sound delivered to the user) than equivalent digitised waveform files.

In contrast to MIDI data, digital audio data is the actual representation of a sound, stored in the form of thousands of individual numbers (called samples). The digital data represents the instantaneous amplitude (or loudness) of a sound at discrete slices of time. Because it is not device dependent, digital audio sounds the same every time it is played. But that consistency comes at a price; large data storage files. Digital sound is used for music CDs.


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.

MIDI data is to digital audio data what vector or drawn graphics are to bitmapped graphics. That is, MIDI data is device dependent; digital data is not. Just as the appearance of vector graphics differs depending on the printer device or display screen, the sounds produced by MIDI music files depend on the particular MIDI device used for playback. Similarly, a roll of perforated player piano score played on a concert grand would sound different than if played on a honky tonk piano. Digital data, on the other hand, produces sounds that are more or less identical regardless of the playback system. The MIDI standard is like PostScript, letting instruments communicate in a well understood language.

(Reference: Multimedia Making It Work, Tay Vaughn, 2001: 205 - 206).

10.2 SOURCE OF AUDIO FILES

Almost all multimedia computers today are equipped with sound cards and speakers; 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 application on a Windows operating system, your action is accompanied with a sound. This sound 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.

After reading the excerpt above, can you state TWO advantages and TWO disadvantages of MIDI compared to digital audio?

Exercise 10.1


10.2.1 PrePackage

Some sound files can be obtained from the computerÊs operating system or from programs that already exist in your computer. Figure 10.3 below shows the sound file that is in Microsoft Office. These sound files can produce special effects such as the sound of doors opening; car braking and others.

10.2.2 Buying and Borrowing

Other than the pre-packages built into an operating system or application software, sound files can also be bought from companies that specialise in production of sound clips. In addition, the Internet is the right place to purchase sound clips. Sometimes you can also get it free by downloading it from the Internet.

These file resources can be very useful for background sounds, sound with special effects and also for historical events, such as speeches or conversations of the Prime Minister.

10.2.3 Own Invention

Sound file can also be produced through your own invention. Sound clips might be created easily by using specific program together with a microphone. One of the factors that must be considered when creating a sound file is the quality of the sound to be generated. If you want to include sound into a PowerPoint presentation, you can use a medium quality sound.

On the other hand, if you aim to produce a commercial of high quality, you should consider using a recording studio equipped with instruments such as DAT (Digital Audio Tape) that can record digital sound. Additionally, sound files can also be generated by using equipment such as an audio synthesiser connected

Figure 10.2: Sound File


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

to the computer so that the sound can be recorded in MIDI (Musical Instrument Digital Interface) format.

Before we proceed to the next topic, make sure that, when obtaining these sources of audio files, you did not infringe or violate the CopyrightÊs Act, which is a critical issue concerning music. To be safe, always make sure that the music you use is royalty free.

10.3 AUDIO SOFTWARE Just like video, attention should also be paid to audio in a multimedia system. Audio management such as recording and editing is very important to generate good multimedia products especially video clips where the audio is synchronised with the video display.

Just like video, audio requires specific software for recording purposes or for the audio production. The Microsoft Windows operating system provides audio recording facility through its software called Sound Recorder (refer Figure 10.3)

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.

Exercise 10.2


Figure 10.3: Sound recorder

For 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 Forge

Sound Forge is professional audio editing software for Windows. It includes an audio processing set, equipment and special effects to manipulate audio. Sound Forge is very useful as it works well with the WindowsÊ compatible sound cards to create, edit and record audio files. This user friendly interface software enables the process of editing to be done quickly and easily.

Sound Forge has special features that make it so popular. Among the special features 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.


10.3.2 SoundEdit 16

This software has features that are almost similar to Sound Forge. It can do editing for more than 10 audio formats. Besides that, it also has Mixer, CD Audio Capture 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 formats from the Internet. SoundEdit 16 also supports compression such as algorithm compression 4:1 for a 16-bit voice. Other than that, you can also import CD tracks directly 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 be done 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 the market. The most popular software to process audio is the Sound Forge. It is easy to use and understand regardless of whether you are a beginner, or have already mastered it. There are several important steps in processing digital audio which are:

(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 Files

Opening and playing sound files is a very basic and easy process with Sound Forge. You can open any number of sound files that you want, simultaneously on the screen.

The first step is to click the File button, then click the Open button as shown in Figure 10.4. If you want to close a file that is not needed, you can click on File and then 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. After opening 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.


Figure 10.4: Opening a Sound File Figure 10.5: Choosing and Opening a Sound File

Meanwhile, you can play the sound file at any starting point by just clicking at different locations using the mouse, and then click on the Play button. Then, you would be able to listen to the sounds, starting from the cursor position till the end of the file.

You can also play part of the sound data by choosing the waveform like indicated on Figure 10.7. You can use the mouse to make the choice. You only need to click the left button of the mouse and drag it to the right side; the black shaded area represents the chosen section. When you click on the Play button, you will only hear the chosen sound.

Figure 10.6: Transport Toolbar


Figure 10.7: Waveform

10.4.2 The Process of Recording and Copying Sound Files

The process of recording and copying sound files is very important. This is the first step in producing a new sound file.

First, you need to insert the compact disc with the sound file sample (.wav), and then click on the Start button in the Windows system. Subsequently, choose Accessories -> Multimedia -> CD Player. A CD player window will be displayed as shown in Figure10.8.

After this window emerges, you can open the Sound Forge window and then click on File -> New. After that, a new window, as shown by Figure 10.9, would

Figure 10.8: CD player window


appear. Here, you should ensure that the sampling rate is 44,100Hz, the sample size is 16-bit and the channel is stereo, and then press the OK button.

Figure 10.9: New file window

A new Sound Forge program window will be displayed. Here, you must coordinate the Sound Forge program window with the CD player window so that both the windows can be seen, as shown in Figure 10.10. This is because you need to 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 change the mode to Automatic retake, input format to Time, and finally mark the Monitor 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.


Figure 10.11: Record Window

When all steps are done, you can click on the Record button, and then click on the Play button which is on the CD player window. After 20 seconds, clik on the Stop button 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 been successfully recorded

10.4.3 The Process of Editing Sound Files

The editing process enables you to do editing or cut MP3 track that you like. The first step is to click on File -> Open. An Open window will be displayed. Then you can choose the required sound file by clicking on the Open button where a main Sound Forge window (Figure 10.12) will be displayed.

Figure 10.12: Main Sound

Forge window


You can play this sound file by just clicking on the Play button to hear the overall sound file, but if you wish to cut out a section (say area A1) of the sound file, you only need to use the mouse to click and drop until you reach the section you wish to discard (Figure 10.13).

After that, click on Edit ·> Delete to discard the selected section. Later, you can store 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 be displayed and then, you need to click the No button. Now you can listen to the song that you have edited.

Figure 10.14: Dialogue box

10.4.4 The Mixing Process

The mixing process is a process of combining two different sounds. This process is started by opening a sound file by clicking File ·> Open. Then, choose the sound file, for example, voiceover.wav which you wish to edit. After choosing the sound file, you can click on the Open button and a waveform can be seen as shown in Figure 10.15.

Figure 10.13: Sound section

(shaded) that you wish to

discard.


Figure 10.15: Waveform for the sound file Voiceover.Wav

You can then choose all the waveform by clicking Edit -> Select All. Then, click Edit ·> Copy. After that, you can open another sound file; letÊs say the sound file, mix.wav. A waveform will be displayed on the screen as shown in Figure 10.16. Now, you may determine the areas that you wished to combine. You can click on any place of the waveform, for example area B2, as shown in the circled area in Figure 10.16.

Then, you can click Edit -> Paste Special -> Mix. A window as shown in Figure 10.17 will be displayed. In the Name box, you should choose Voice Over Mix, and then 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.

Figure 10.16: Waveform for

Mix.wav file


10.4.5 Compression Process for Internet Use

Sometimes we wish to export a sound file via the Internet, but the huge file size causes the sending process to become slow. As such, this software is able to compress the required sound file. If you want to compress a sound file, in the first place, you should open the file by clicking File -> Open, and choose the required sound 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 10.17: Mix window

Figure 10.18: Properties window


Now, you can click on Process -> Resample. A Resample window will be displayed as shown in Figure 10.19. At the Name window, choose 22,050Hz with anti-alias filter, and then click the OK button.

Now, the compression process has been successfully executed. The selected sound 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 as type and choose, NeXT/ Sun(Java) File (*.au, *.snd) from the drop down list. Also go 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

Try editing a sound file using Sound Forge software without referring to this

book. What are your opinions on this software?

YOUR IDEA

Figure 10.19: Resample window


SUMMARY

To integrate the audio element into a multimedia project, you do not require a deep knowledge of sound. However, you should equip yourself with the basic knowledge as to how sound is produced, know the audio file formats and learn how to record and edit sounds on the computer. Thus, this chapter has presented to you, several file formats used to record digital audio. You also know the differences between digital audio and MIDI. At the end of this chapter, you also learned several basic techniques on how to generate an audio file with the use ofthe Sound Forge software.

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.

Exercise 10.3

chapter10

Technology