Download ppt - Scct2013 topic 4_audio

Audio

•This is a necessary element in a multimedia product.

•In general, the audio associated with hearing sense or the noise produced briefly known as the audio.

•Audio is able to influence the emotions and thoughts of human and be able to attract users.

•They provide a clear picture of a difficult concept rather than using text or graphics alone.

Introduction

•As an example, the arrangement of words that form a text to reflect the atmosphere of war. Through the text, the individual can imagine things happening, but with the help of audio, individuals will have better understanding and improve the emotional involvement to stay in the conflicts in a clear and focused.

Audio

Introduction (Cont.)

•Basically, when we listen, we have been feeling the changes in air pressure around us.

•This change is received by the eardrum and then the impulses are sent and interpreted as a signal of sound by the brain.

•When no sound waves present, the air pressure is constant.

•When sound waves reach the eardrum, the air pressure will change that either high or low rates.

Concept of Audio and Audio Wave

•Audio files can be divided into two types, analogue audio and digital audio.

•Original sound can be heard through our ears like drums, birds twittered, singing live and others are examples of analogue audio.

•It is a continuous flow of sound waves.

Types of Audio File & Compression File

•The following is an analogue waveform and digital waveform.

Types of Audio File & Compression File(Cont.)

Analogue Waveform

Digital Waveform

•Digital audio file is a digital audio file that has been translated (convert) in a digital form.

•The aim is to enable computers to understand the wave that is converted into the form of numbers or binary (0 and 1).

•This process is called digitization of audio or audio sampling.

•In the context of this module, the notes basically cover more on digital audio.

Types of Audio File & Compression File(Cont.)

•Audio compression is one way to reduce the size of audio files.

•There are two types of compression can be used:1. Lossless Compression2. Lossy Compression

Audio Compression

Lossless Compression

•This compression can compress the files without reducing the quality drop compared to lossy compression.

•Each repetition of the information will use the concept of representation and not have to repeat the full details again and again.

Audio Compression (Cont.)

Lossy Compression

•This compression causes data quality after compression to be relatively low compared to Lossless compression.

•This is because some of the data or information in the file continues to be ignored or discarded.

•the results can still be accepted by human hearing.

Audio Compression (Cont.)

1.0 Sample Rate •It refers to the number of samples of a

sound that are taken per second. •The higher the sample rate and more

information on the samples taken, the higher quality digital audio.

•Sample rate is measured in Hertz (Hz). •Standard sampling rates typically used for

an audio recording is 11,025 kHz, 22.05 kHz and 44.1 kHz.

Factors Affecting the Quality Audio

2.0 Sample Size •It refers to the amount of information stored

in a sample OR the number of bits used to store information of the audio.

•Two types of sample size used is 8 bits or 16 bits.

•Audio recorded by using a sample size of 16 bits has better quality compared to 8-bit sample size.

•Type of sample size chosen for this audio recording was also influenced by the quality of sound card – 16 bit or 8 bit.

Factors Affecting the Quality Audio(Cont.)

3.0 Channel •There are two types of channels are often

used in audio recording:-1. Mono2. Stereo

Factors Affecting the Quality Audio(Cont.)

1.0 Audio Interchange File Format (AIFF and AIF)

•often used in computer systems of the Macintosh, IBM and IBM-compatible.

•It holds a variety of different levels of sample size (up to 32 bits).

•AIFF formats are usually not able to perform data compression as AIFF files are usually larger than other formats.

Audio File Format

2.0 Musical Instrument Digital Interface (MID, MIDI, and MFF)

•format adopted around the world aim to keep the audio from the types of MIDI.

•MIDI is the standard language used for communication between musical instruments and computers.

•This means that a musician can use electronic keys, guitar and other MIDI equipment to synthesizing audio to be connected to a personal computer.

Audio File Format (Cont.)

3.0 Resource Interchange File Format (RIFF)

•This file format introduced by Microsoft and it may contain various types of data including audio in form of wave as well as MIDI.

4.0 Sound (SND) •This file format was introduced by Apple and

only used for audio with 8-bit sample size.


5.0 Wave (WAV) •This file format most widely used. •It was developed by Microsoft and can

support recording with sample size up to 8-bit and 16 bits (mono and stereo).

•WAV files are usually large and depends on the length of the recorded audio as well as the sampling rate used for recording.


6.0 Sun Audio (AU) •It introduced specially for Sun Microsystems

workstations. •It is 16 bit audio formats compressed, and

are used for the purpose of dissemination through the Internet.

7.0 Real Audio or Real Media (RAM and RA)

•It is the most common file format used for audio transmission via the Internet directly.

•It also enables the radio and television screened directly via the Internet.


8.0 MPEG Level 3 (MP3) •audio file format that is increasingly popular,

especially for the purpose of online distribution of music via the Internet.

•It has a good file compression technique can compress audio up to size 45 MB in wav format to about 4 MB only in MP3 format.


•Generally there are two main methods of of digital audio data, namely: 1. The wave (Waveform Audio). 2. Musical Instrument Digital Interface

(MIDI).

Storage Management

1.0 Waveform Audio

•This is the audio that was recorded in digital form and stored in secondary storage.

•This audio is then played back through the existing sound card in a computer system.

•Wave contains samples of the amplitude (height of the voice) of audio taken at a specified time (frequency) and then played back at an appropriate rate.

Storage Management (Cont.)

2.0 MIDI•It is actually not an audio format. •It is mostly a form of the interface to produce an audio.

•This audio is then stored in MIDI format. •MIDI sound is produced by pressure on the keyboard will be encoded as a series of instructions and finally stored as a file and the music score can be sent from computer to another electronic equipment.

Storage Management (Cont.)