Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03 Modern Trends in Audio Compression presented...

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Modern Trends in

Audio Compression

presented by

Ognen Paunovski

Andon Dragomanov

2nd International Student Spring Symposium in Contemporary Topics in IT

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Agenda

Idea Behind the Compression Lossy and Lossless Compressions Key Terms Compression Algorithms

MP3 - Format Ogg Vorbis -Format WMA – Format Format Comparison

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

In general Compression refers to a variety of ways (algorithms) to

reduce the size of a data file.

IMPORTANT Compression makes downloading quicker and lessens the amount of storage space needed on a hard drive.

The Idea Behind the Compression

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Lossy -

Lossless -

Lossy vs. Lossless Compression

After one applies lossy data compression to

a file, the file can never be recovered exactly

as it was before it was compressed.

In a lossless data compression file

after the operation of compression and

decompression will be restored to its

original format.

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Key Terms

Wave Form

Sample Bit Rate

(CBR, VBR)

Sample Rate

Code Word

Quantization

Digitalization

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Dictionary Methods

Huffman Coding

PCM Pulse Code Modulation

DPCM Differential PCM

Compression Algorithms

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Creation Process Stages: Separation into Frames Spectral Analysis “Masking” ( Psychoacoustic Models ) Processing ~ Bit Rate & Joint Stereo Compressing ( Hoffman ZIP )

CBR & VBR Most Popular

Many codec's and players

Specific Audio Formats – MP3

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Specific Audio Formats – Ogg Vorbis

Creation Process Stages: Same as those in MP3

Improvements over MP3 Designed for Streaming Connection Real Stereo ~ No Multiplexing Multi-Channel Support (more than Mono & Stereo) Bit Rate Scaling

Preferred VBR New Codec

Free Source Code One codec and few players

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Specific Audio Formats – WMA

Advanced System Format (ASF) including: Support for Meta Data Scripting Security Features

CBR & VBR (only after version 9) Industrial Support

Free Codec Few Players

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Comparison

WAV

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Comparison

MP3

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Comparison

OGG

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Comparison

WMA

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Comparison

WAV MP3 OGG WMA

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

Comparison (Cont.)

0

100

200

300

400

500

600

Low Quality High Quality

MP3

OGG

WMA

From a WAV File with size 3,85 MB

KB

Mar 2003 Ognen Paunovski :: Andon Dragomanov S3CTIT03

THANK YOU!