Kolej Kemahiran Tinggi MARA                            Rembau, Negeri Sembilan                                    INFORMAT...
UNIT 1: Introduction to Digital Audio System1. Digital audio is the process of converting media from analog to digital for...
1.1.    History of AudioHistory of Audio FormatAn audio format is a medium for storing sound and music. Music is recorded ...
1925            Electrical cut record                  Mechanical analog; electrically cut from amplified                 ...
1965            8-Track (Stereo-8)                     Analog, 1/4 inch wide tape, 3 3/4 in/s, endless loop               ...
1982                                                   PCM                    Compact Disc (CD-DA)1985                    ...
1997            DTS-CD                                 DTS Audio1999            DVD-Audio1999            Super Audio CD (S...
History of Sound Recording1. Mechanical Recording       The first devices for recording and reproducing sound were mechan...
 Recording could be played back by tracing a needle through the groove and        amplifying, through mechanical means, t...
 The advent of electrical recording made it possible to use microphones to capture the        sound of the performance3. ...
 In the late 1950s the cinema industry, desperate to provide a theatre experience that        would be overwhelmingly sup...
data. For example, telephones take sound vibrations and turn them into electrical          vibrations of the same shape be...
1.3 File Size1. Sound file contain large amount of data and uncompress they are huge2. A sound file generally has audio da...
1.4 Digital Audio FormatLet us firstly look at the file formats commonly used:1. WAV              Developed by Microsoft ...
6. MIDI                 MIDI as you’ve learned is very2 small in file size                 But the only thing they’re go...
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  1. 1. Kolej Kemahiran Tinggi MARA Rembau, Negeri Sembilan INFORMATION SHEETCOURSE: Digital Video And AudioSESSION : July-Dec 2012 SEMESTER : 3CODE/SUBJECT : SHEET NO : 1LECTURER : Ahmad Kamsol Bin Mat Yusop WEEK : 1TOPIC : Introduction to Digital Audio System 1.1. History 1.2. Understand Analog and Digital AudioSUB-TOPIC : 1.3. File Size 1.4. Digital Audio Format After completing this chapter, students will be able to: 1. Understand the history of digital audio systemLEARNING 2. Understand the different between analog and digital audioOUTCOME : 3. Explain type of file size in digital audio system 4. Interpret about digital audio formatDigital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  2. 2. UNIT 1: Introduction to Digital Audio System1. Digital audio is the process of converting media from analog to digital form (digitizing) is achieved through a process called sampling.2. The most common method of creating digital audio is Pulse-code modulation (PCM)ADCs and DACs Real sound input ADC - Analog to Digital Converter -Recorder through microphone Reproduce sound DAC - Digital to Analog ConverterSampling Process 1. Here is an analog 2. To digitize sound, 3. These samples are sound wave. Analog samples are taken at trimmed to the nearest sound is continuous even intervals of times value and encoded in variation in air binary pressure.Digital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  3. 3. 1.1. History of AudioHistory of Audio FormatAn audio format is a medium for storing sound and music. Music is recorded and distributedusing a variety of audio formats, some of which store additional informationTimeline of audio format developments. Year Media formats Recording formats1877 Mechanical analog; "hill-and-dale" grooves, vertical stylus motion Phonograph cylinder1883 Mechanical digital (automated musical instruments) Music roll1895 Mechanical analog; lateral grooves, horizontal stylus motion Gramophone record1898 Analog; magnetization; no "bias" Wire recordingDigital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  4. 4. 1925 Electrical cut record Mechanical analog; electrically cut from amplified microphone signal, lateral grooves, horizontal stylus motion, discs at 7", 10", 12", most at 78 rpm1930 Analog; magnetization; "bias" dramatically increases linearity/fidelity, tape speed at 30 ips, later 15 ips with NAB equalization; refined speeds: 7 1/2 ips, 3 3/4 ips, 1 7/8 ips Reel-to-Reel, Magnetic Tape1930 Electrical transcriptions Mechanical analog; electrically cut from amplified microphone signal, high fidelity sound, lateral or vertical grooves, horizontal or vertical stylus motion, most discs 16" at 33 1/3 rpm1948 Analog, with preemphasis and other equalization(Commercial techniques (LP, RIAA); lateral grooves, horizontalrelease) stylus motion; discs at 7" (most 45 rpm), 10" and 12" (most 33 1/3 rpm) Vinyl Record1957 Stereophonic Vinyl Record Analog, with preemphasis and other equalization techniques. Combination lateral/vertical stylus motion with each channel encoded 45 degrees to the vertical.1962 4-Track (Stereo-Pak) Analog, 1/4 inch wide tape, 3 3/4 in/s, endless loop cartridge.1963 Analog, with bias, preemphasis, 0.15 inch wide tape, 17/8 in/s. 1970: introduced Dolby noise reduction. Compact CassetteDigital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  5. 5. 1965 8-Track (Stereo-8) Analog, 1/4 inch wide tape, 3 3/4 in/s, endless loop cartridge.1969 Analog, 1/8 inch wide tape, used generally for notetaking, mostly mono, some stereo. 2.4 cm/s or 1.2 cm/s. Microcassette1970 Quadraphonic 8-Track Analog, 1/4 inch wide tape, 3 3/4 in/s, 4 Channel (Quad-8) (Q8) Stereo, endless loop cartridge.1971 Quadraphonic Vinyl Record (CD-4) (SQ Matrix)1975 Dolby Stereo cinema surround sound Betamax Digital Audio1976 Elcaset1978 LaserdiscDigital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  6. 6. 1982 PCM Compact Disc (CD-DA)1985 Audio Interchange File Format (AIFF)1985 Sound Designer (by Digidesign)1986 High Definition Compatible Redbook compatible physical CD containing 20-24 Digital (HDCD) bit information.1987 Digital Audio Tape (DAT)1991 MiniDisc (MD) ATRAC1992 Digital Compact Cassette (DCC)1992 Waveforms (WAV) Dolby Digital surround cinema sound1993 Digital Theatre System (DTS) Sony Dynamic Digital Sound (SDDS)1995 MP31997 DVD Dolby DigitalDigital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  7. 7. 1997 DTS-CD DTS Audio1999 DVD-Audio1999 Super Audio CD (SACD)1999 Windows Media Audio (WMA)1999 The True Audio Lossless Codec (TTA)2000 Free Lossless Audio Codec (FLAC)2001 Advanced audio coding (AAC)2002 Ogg Vorbis2003 DualDisc2004 Apple Lossless (ALE or ALAC)2005 HD DVD2005 OggPCM2006 Blu-Ray2008 slot Music 320kb/s MP3 on microSD or microSDHCDigital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  8. 8. History of Sound Recording1. Mechanical Recording  The first devices for recording and reproducing sound were mechanical in nature and could not record arbitrary sounds such as the human voice.  In 1796 a Swiss watchmaker named Smooth Nikola described his idea for what we now call the cylinder musical box. - Phonautograph  1857, Edouard-Leon Scott de Martinville invented the phonautograph, the first device to record arbitrary sound.  Used a membrane (which vibrated in response to sound) attached to a pen, which traced a line roughly corresponding to the sounds waveform onto a roll of paper -Phonograph and Gramophone  Phonograph Invented by Thomas Edison in 1877  phonograph was a device with a cylinder covered with a hard material such as tin foil, lead, or wax on which a stylus drew grooves  The depth of the grooves made by the stylus corresponded to change in air pressure created by the original sound.Digital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  9. 9.  Recording could be played back by tracing a needle through the groove and amplifying, through mechanical means, the resulting vibrations Edisons cylinder-based Phonograph The disk-based gramophone..Cont: Phonograph and Gramophone  A disadvantage of the early phonographs was the difficulty of reproducing the phonograph cylinders in mass production.  This changed with the advent of the gramophone (phonograph in American English), which was patented by Emile Berliner in 1887  The gramophone imprinted grooves on the flat side of a disc rather than the outside of a cylinder  Instead of recording by varying the depth of the groove (vertically), as with the phonograph, the vibration of the recording stylus was across the width of the track (horizontally)2. Electrical Recording  Both phonograph cylinders and gramophone discs were played on mechanical devices most commonly hand wound with a clockwork motor.  The sound was amplified by a cone that was attached to the diaphragm  The disc record fell into public favor quickly, and cylinders were not produced after 1929  The advent of electrical recording in 1925 drastically improved the quality of the recording process of disc records  Electrically powered phonographs were introduced c. 1930, but crystal pickups and electronic reproduction did not become common until the late 1930s.Digital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  10. 10.  The advent of electrical recording made it possible to use microphones to capture the sound of the performance3. Magnetic Recording  Magnetic recording was demonstrated in principle as early as 1898 by Valdemar Poulsen in his telegraphone  Magnetic wire recording, and its successor, magnetic tape recording, involve the use of a magnetizable medium which moves with a constant speed past a recording head  electrical signal, which is analogous to the sound that is to be recorded, is fed to the recording head, inducing a pattern of magnetization similar to the signal  A playback head can then pick up the changes in magnetic field from the tape and convert it into an electrical signal.  1932 the British Broadcasting Corporation first used a steel tape recorder for their broadcasts4. Recording On Film  The first attempts to record sound to an optical medium occurred around 1900  1906 Lauste applied for a patent to record sound on film, but was ahead of his time  In 1923 Lee de Forest applied for a patent to record to film; he also made a number of short experimental films, mostly of vaudeville performers  William Fox began releasing sound-on-film newsreels in 1926, the same year that Warner Brothers released Don Juan with music and sound effects recorded on discs, as well as series of short films with fully synchronized sound on discs  In 1927 the sound film The Jazz Singer was released; while not the first, it made a tremendous hit and made the public and the film industry realize that sound film was more than a mere novelty  There are really two different types of synchronized film soundtrack, optical and magnetic  Optical sound tracks are visual renditions of sound wave forms and provide sound through a light beam and optical sensor within the projector  Magnetic sound tracks are essentially the same as used in conventional analog tape recordingDigital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  11. 11.  In the late 1950s the cinema industry, desperate to provide a theatre experience that would be overwhelmingly superior to television, introduced wide-screen processes such as Cinerama, Todd-AO, and CinemaScope.  In the 1990s, digital systems were introduced and began to prevail. Ironically, in many of them the sound recording is, as in Vitaphone, again recorded on a separate disk; but now, digital processes can achieve reliable and perfect synchronization5. Digital recording  The first digital audio recorders were reel-to-reel decks introduced by companies such as Denon (1972), Soundstream (1979) and Mitsubishi  Used a digital technology known as PCM recording  Within a few years, many studios were using devices that encoded the digital audio data into a standard video signal, which was then recorded on a U-matic or other videotape recorder, using the rotating-head technology that was standard for video  Similar technology was used for a consumer format, Digital Audio Tape (DAT) which used rotating heads on a narrow tape contained in a cassette  In the early 1990s, relatively low-priced multitrack digital recorders were introduced for use in home studios; they returned to recording on videotape.  The development of the MP3 audio file format, and legal issues involved in copying such files, has driven most of the innovation in music distribution since their introduction in the late 1990s  At the end of the 1990s, hard disk recording became more popular1.2 Understanding Analog and Digital AudioAnalog  Also spelled analogue, describes a device or system that represents changing values as continuously variable physical quantities.  A typical analog device is a clock in which the hands move continuously around the face  When used in reference to data storage and transmission, analog format is that in which information is transmitted by modulating a continuous transmission signal, such as amplifying a signals strength or varying its frequency to add or take awayDigital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  12. 12. data. For example, telephones take sound vibrations and turn them into electrical vibrations of the same shape before they are transmitted over traditional telephone lines  Radio wave transmissions work in the same way. Computers, which handle data in digital form, require modems to turn signals from digital to analog before transmitting those signals over communication lines such as telephone lines that carry only analog signals. The signals are turned back into digital form (demodulated) at the receiving end so that the computer can process the data in its digital format.Digital  Describes any system based on discontinuous data or events  Computers are digital machines because at their most basic level they can distinguish between just two values, 0 and 1, or off and on. There is no simple way to represent all the values in between, such as 0.25. All data that a computer processes must be encoded digitally, as a series of zeroes and ones  Digital clock is capable of representing only a finite number of times (every tenth of a second, for example)Digital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  13. 13. 1.3 File Size1. Sound file contain large amount of data and uncompress they are huge2. A sound file generally has audio data and metadata3. Audio data is sound that you hear4. Metadata can include the name of the sound file, its size, duration, number of channels, resolution or sample size (in bits), sampling rate (in kilohertz), types of compression, information about streaming, special instruction, text or graphic. Amplitude Type of Sound 130 dB Gunshot @5 feet 120 dB Live Rock Band @10 feet 110 dB Loud Car Stereo (interior) 90 dB Underground Train Station + The Train 80 dB A Busy Street 70 dB Vacuum Cleaner @10 feet A Conversation @5 feet 60 dB An office cubicle 50 dB En. Alfian’s office with air-con turned off 40 dB A Whisper @5feet 30 dB Very Quiet Room 20 dB A Recording StudioDigital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  14. 14. 1.4 Digital Audio FormatLet us firstly look at the file formats commonly used:1. WAV  Developed by Microsoft (intended for Intel-based computers)  Comes with the file extension *.wav  16-bit wav has high sound quality, but the tradeoff is with size  Very low compression  8-bit wav has medium sound quality, but medium file size2. AIFF  Developed primarily for use on the MAC  Come with a few extensions  *.aif, *.aiff, *.aife  16-bit and 8-bit AIFFs have almost similar properties with its WAV counterpart3. AU or MU- LAW or u-LAW  Most prevalent on the web (platform independent) and also needs plug-in to play  Comes with a *.au extension  Medium file sizes but bad sound quality (suitable for web though due to its size)4. MP3  One of the best known formats around  Achieves quite high compression rates while maintaining good sound quality  Extension = *.mp3  Is actually MPEG-1 Audio Layer Layer-3  Good sound quality (with data rate of above 128 kbps that is), good compression (only ~10% of CD-Audio)5. RM  Format by RealNetworks  Extension = .ra, *.rm, *.ram  Advantage = Real-time playability, small file size  Disadvantage = Very not-good sound qualityDigital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1
  15. 15. 6. MIDI  MIDI as you’ve learned is very2 small in file size  But the only thing they’re good at is producing musical-instrument-sound   Advantage = Small file size  Disadvantage = Not suitable for dialogue  Extension = *.mid, *.midi, *.kar, *.smfREFERENCES:Book: Vaughan T., 2004, Multimedia: Making It Work, 6th Ed, McGraw-Hill, UK.Web: http://homepages.cwi.nl http://en.wikipedia.org/wiki/Authoring_systems http://www.cit.cornell.edu/atc/materials/dig/audioformats.shtml Digital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1

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