Slide đa phương tiện chương 1 audio

Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi c om Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology ng th an co ng Audio and speech signal processing cu u du o Tien Pham Van, Dr rer nat Hanoi University of Science and Technology CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi cu u du o ng th an co ng • Concepts • Signal characteristics • Compression techniques c om Agenda CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi The Nature of Sound ng c om • Sound is a physical phenomenon produced by the vibration of matter and transmitted as waves cu u du o ng th an co • However, the perception of sound by human beings is a very complex process It involves three systems: - the source which emits sound; - the medium through which the sound propagates; - the detector which receives and interprets the sound CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi th an co ng c om • Sounds we heard everyday are very complex Every sound is comprised of waves of many different frequencies and shapes But the simplest sound we can hear is a sine wave cu u du o ng • Sound waves can be characterised by the following attributes: Period, Frequency, Amplitude, Bandwidth, Pitch, Loudness, Dynamic CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi Pitch and Frequency th an co ng c om • Period is the interval at which a periodic signal repeats regularly • Pitch is a perception of sound by human beings It measures how ‘high’ is the sound as it is perceived by a listener • Frequency measures a physical property of a wave It is the reciprocal value of period f = 1/P The unit is Herts (Hz) or kiloHertz (kHz) u du o ng Infra-sound – 20 Hz Human hearing range 20 – 20 kHz Ultrasound 20 kHz – GHz Hypersound GHz – 10 THz cu • • • • • Musical instruments are tuned to produce a set of fixed pitches CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi c om The characteristics of sound waves Time for one cycle co ng Amplitude distance along wave Cycle cu u du o ng th an pitch CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi Loudness and Amplitude c om • The other important perceptual quality is loudness or volume co ng • Amplitude is the measure of sound levels For a digital sound, amplitude is the sample value cu u du o ng th an • The reason that sounds have different loudness is that they carry different amount of power • The unit of power is watt The intensity of sound is the amount of power transmitted through an area of 1m2 oriented perpendicular to the propagation direction of the sound • If the intensity of a sound is 1watt/m2, we may start feel the sound The ear may be damaged CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi co ng c om • This is known as the threshold of feeling If the intensity is 10-12watt/m2, we may just be able to hear it This is know as the threshold of hearing cu u du o ng th an • The relative intensity of two different sounds is measured using the unit Bel or more commonly deciBel (dB) It is defined by relative intensity in dB = 10 log(I2/I1) • Very often, we will compare a sound with the threshold of hearing CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology u du o ng th an co ng c om 160 dB Jet engine 130 dB Large orchestra at fortissimo 100 dB Car on highway 70 dB Voice conversation 50 dB Quiet residential areas 30 dB Very soft whisper 20 dB Sound studio cu • • • • • • • Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi c om Dynamic and Bandwidth ng th an co ng • Dynamic range means the change in sound levels • For example, a large orchestra can reach 130dB at its climax and drop to as low as 30dB at its softest, giving a range of 100dB • Bandwidth is the range of frequencies a device can produce, or a human can hear cu u du o e.g FM radio: Children’s ears: Older ears: 50Hz – 15kHz 20Hz – 20kHz 50Hz – 10kHz 10 CuuDuongThanCong.com https://fb.com/tailieudientucntt Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi cu u du o ng th an co ng c om Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi AAC (Continue) • Compression techniques Huffman coding Non-linear quantization and scaling Vector quantization M/S matrixing (middle/side channels) for high bitrates Intensity stereo for low bitrates TNS (temporal noise shaping) LTP(MPEG4 profile 2, reduce redundancy in successive frames) – MDCT – PNS (perceptual noise shaping) cu u du o ng th an co ng c om – – – – – – – CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi c om Digital audio editing software cu u du o ng th an co ng  One of the most powerful and professional PC-based packages is a tool called Sound Forge CuuDuongThanCong.com http://www.sonicfoundry.com/ https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi cu u du o ng th an co ng Trimming Splicing and assembly Volume adjustments Format conversion Resampling or downsampling Fade ins and fade outs Equalization Time Stretching Digital Signal processing Reversing Sounds c om Editing Digital Audio CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi Editing Digital Audio Simple audio editing software allows:  c om ng du o  co  an  th  Recording of digital audio segments Trimming Splicing and assembly Volume adjustments of the entire segment Reversing Sounds Copy, cut, paste and delete segments of digital audio ng      cu u Others audio editing software: COOL Edit Pro Gold Wave PROSONIQ SonicWORX Samplitude Studio CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi c om Audio formats Depend on O/S For examples: AIFF (Audio Interchange File Format)  SOU an For Macintosh  Waveform file format For Windows/Microsoft u  du o WAV cu  ng th  co ng  VOC  Sound Blaster Card CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi MIDI (Musical Instrument Digital Interface) ng c om MIDI is a standard for specifying a musical performance du o ng th an co Rather than send raw digital audio, it sends instructions to musical instruments telling them what note to play, at what volume, using what sound, etc cu u The synthesiser that receives the MIDI events is responsible for generating the actual sounds Example: Keyboard Piano CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology ng co an th ng du o cu u • A MIDI sequencer allows musicians to edit and create musical compositions like a word processor – Cut and paste – Insert / delete c om MIDI sequencers Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi MIDI Versus Wav ng c om Quality recording, MIDI depend to the tools Audio wav easier to create than MIDI an du o ng  File Size small Size Storage also small th  co MIDI Advantages u MIDI Advantages  Playback Cost and Skill cu  CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi c om How audio can be used effectively ng Examples of uses of audio: th an co  Cautions and warnings It is a good medium for alerting users to critical information Some uses include: ng cu u  Sounding an alarm when a limit is reached Alerting users when data is entered incorrectly du o   Music and Sound Effects These make multimedia interaction more real Some uses include: CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi th an co  Musical background for a video segment Birds Songs accompanying photographs in biological field training ng  c om How audio can be used effectively du o ng  Sound-related data Some uses include:  u Helping mechanics diagnose engine trouble Training medical students to recognize different breathing sounds cu  CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi c om How audio can be used effectively co Leaving a voice message for other users of an application Consulting with an expert during a troubleshooting procedure du o u cu  ng th an  ng  Direct voice communication Some uses include: CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi c om Advantages and Disadvantages of using audio co ng Sound adds life to any multimedia application and plays important role in effective marketing presentations ng th an  Advantages Ensure important information is noticed  Add interest  Can communicate more directly than other media cu u du o  CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi c om Advantages and Disadvantages of using audio co ng  Disadvantages Easily overused  Requires special equipment for quality production  Not as memorable as visual media cu u du o ng th an  CuuDuongThanCong.com https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat , Embedded Networking Research Group Faculty of Elec and Telecom, Hanoi University of Science and Technology Email: tien.phamvan1@hust.edu.vn C9-411 Dai Co Viet str 1, Hanoi Homework an co ng c om • Install Matlab • Record/download an digital audio file • Write scripts to perform different audio coding/transforming strategies: LPC, CELP, MP3, etc • Decode the compressed file and play back, then comment on sound quality • References: cu u du o ng th – http://www.mathworks.com/help/signal/ref/lpc.html – http://www.mathworks.com/matlabcentral/fileexchange/3903 8-celp-codec/content/CELP_done/CELP_RUN.m – http://homepages.udayton.edu/~hardierc/ece203/sound.htm – http://www.mathworks.com/matlabcentral/fileexchange/1385 2-mp3read-andmp3write/content/mp3readwrite/html/demo_mp3readwrite html CuuDuongThanCong.com https://fb.com/tailieudientucntt ... at the first 16 of the 32 bands): c om • Level 12 10 10 60 35 10 11 12 13 14 15 16 20 15 ng an co ng th The 60dB level of the 8th band gives a masking of 12 dB in the 7th band, 15 dB in the 9th... into voltage ADC CuuDuongThanCong.com Signal is converted into binary (discrete form) 010 10 011 01 011 010 111 1 Air pressure variations https://fb.com/tailieudientucntt Pham Van Tien, Dr rer nat ,... tien.phamvan1@hust.edu.vn C9- 411 Dai Co Viet str 1, Hanoi Effectiveness of MPEG Audio 19 2 kbps 4 :1 Layer II 12 8 kbps 6 :1 Layer III 64 kbps c om Layer I Quality* at 64 kbps an th 12 :1 Quality at 12 8 kbps