Multimedia:  Digitised Sound Data Section 3
Sound in Multimedia <ul><li>Types: </li></ul><ul><li>Voice Overs </li></ul><ul><li>Special Effects </li></ul><ul><li>Music...
Sound Capture <ul><li>Microphone: </li></ul><ul><ul><li>Analogue </li></ul></ul><ul><ul><li>Can be used for voice-overs </...
Sampling Frequency <ul><li>Once an analogue signal is received it is chopped up and a  sample  is taken </li></ul><ul><li>...
Sampling Frequency <ul><li>Measurements (or samples) will be taken many times each second </li></ul><ul><li>The sampling r...
Sampling Depth <ul><li>This describes the number of bits which are taken in each sample </li></ul><ul><ul><li>This will de...
Multimedia:  Digitised Sound Data Storage of Sound Data
RAW <ul><li>Uncompressed  audio data </li></ul><ul><li>Sampled digital data which has not been processed further </li></ul...
RAW <ul><li>When data from PAM (Pulse Amplitude Modulation) is stored  sequentially  it is called  Pulse Code Modulation (...
RIFF <ul><li>Resource Interchange File Format </li></ul><ul><li>It is a  container file </li></ul><ul><ul><li>It can conta...
WAV File <ul><li>Wave files are RIFF files containing digitised sound data </li></ul><ul><li>They are commonly encoded usi...
MP3 <ul><li>MPEG Audio Layer-3   (MP3) </li></ul><ul><li>Uses  lossy  compression </li></ul><ul><li>Based on what humans h...
File Size Vs Quality <ul><li>Sampling depth : </li></ul><ul><ul><li>increased sound depth </li></ul></ul><ul><ul><ul><li>G...
Comparing Bitmap image files and digitised sound files <ul><li>Each sample records data for a pixel </li></ul><ul><ul><li>...
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Mm Unit 3

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  • Mm Unit 3

    1. 1. Multimedia: Digitised Sound Data Section 3
    2. 2. Sound in Multimedia <ul><li>Types: </li></ul><ul><li>Voice Overs </li></ul><ul><li>Special Effects </li></ul><ul><li>Musical Backdrops </li></ul>Sound can make multimedia presentations dynamic and interesting. They can also be used to assist user.
    3. 3. Sound Capture <ul><li>Microphone: </li></ul><ul><ul><li>Analogue </li></ul></ul><ul><ul><li>Can be used for voice-overs </li></ul></ul><ul><li>CD/DVD: </li></ul><ul><ul><li>Digital </li></ul></ul><ul><ul><li>Capturing music files </li></ul></ul><ul><ul><li>Copyright laws may apply </li></ul></ul>
    4. 4. Sampling Frequency <ul><li>Once an analogue signal is received it is chopped up and a sample is taken </li></ul><ul><li>The sampling frequency is the number of samples taken per second. </li></ul>Sound Wave Samples of Sound Wave
    5. 5. Sampling Frequency <ul><li>Measurements (or samples) will be taken many times each second </li></ul><ul><li>The sampling rate for audio CD is 44.1kHZ means 44100 thousand samples per second. </li></ul>
    6. 6. Sampling Depth <ul><li>This describes the number of bits which are taken in each sample </li></ul><ul><ul><li>This will determine the dynamic range of the recording </li></ul></ul><ul><ul><li>An audio CD will have a sampling depth of 16bits (65536 levels) </li></ul></ul>
    7. 7. Multimedia: Digitised Sound Data Storage of Sound Data
    8. 8. RAW <ul><li>Uncompressed audio data </li></ul><ul><li>Sampled digital data which has not been processed further </li></ul><ul><li>The process of sampling he analogue signal and quantising depending on the strength of the signal (amplitude) is called Pulse Amplitude Modulation (PAM) </li></ul>
    9. 9. RAW <ul><li>When data from PAM (Pulse Amplitude Modulation) is stored sequentially it is called Pulse Code Modulation (PCM) </li></ul><ul><li>PCM allows digital data to be transmitted over a network or to a sound card as it is easily decoded and used to construct the original sound as it is being received. </li></ul>
    10. 10. RIFF <ul><li>Resource Interchange File Format </li></ul><ul><li>It is a container file </li></ul><ul><ul><li>It can contain various types of data (e.g. video, bitmaps, sound, etc) </li></ul></ul><ul><li>RIFF is a multimedia file format. The type of information stored is stated by the header. </li></ul>
    11. 11. WAV File <ul><li>Wave files are RIFF files containing digitised sound data </li></ul><ul><li>They are commonly encoded using Adaptive Differential Pulse Code Modulation (ADPCM) </li></ul><ul><li>Often used in places such as digital telephone systems and minidisc players. </li></ul>
    12. 12. MP3 <ul><li>MPEG Audio Layer-3 (MP3) </li></ul><ul><li>Uses lossy compression </li></ul><ul><li>Based on what humans hear best </li></ul><ul><ul><li>Perceptual Audio Compression </li></ul></ul><ul><li>Reduces RAW formats to around 10% of original size </li></ul><ul><ul><li>3min of CD quality song = 30Mb </li></ul></ul><ul><ul><li>3min of MP3 = 3Mb </li></ul></ul><ul><li>Quality is adjustable </li></ul>
    13. 13. File Size Vs Quality <ul><li>Sampling depth : </li></ul><ul><ul><li>increased sound depth </li></ul></ul><ul><ul><ul><li>Greater range of values </li></ul></ul></ul><ul><ul><ul><li>Better sound quality and greater file size. </li></ul></ul></ul><ul><li>Sampling frequency: </li></ul><ul><ul><li>The higher the sampling frequency, the better the sound quality, the greater the file size. </li></ul></ul><ul><li>Sound time: </li></ul><ul><ul><li>Longer track lasts the larger the file size </li></ul></ul><ul><ul><li>Affects file size but not quality. </li></ul></ul>
    14. 14. Comparing Bitmap image files and digitised sound files <ul><li>Each sample records data for a pixel </li></ul><ul><ul><li>Bitmap: Resolution </li></ul></ul><ul><ul><li>Sound: Frequency </li></ul></ul><ul><li>Bitmap: Number of bits for each sample/number of colours used </li></ul><ul><ul><li>Colour depth </li></ul></ul><ul><li>Sound: Number of bits determines number of signal levels that can be recorded </li></ul><ul><ul><li>Sampling Depth </li></ul></ul>

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