SC_I_01_Intro_4 - Signal Compression 1 Signal Compression 2...

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Signal Compression 1 Copyright © 2005 – 2008 Hayder Radha Compression Systems Compression systems traditionally include multiple stages at the encoder/transmitter side and a corresponding set of stages at the decoder/receiver side : ± First, we need to prepare the signal for compression; in other words, most signals are not immediately ready or not suitable to be compressed in Signal Compression 2 Copyright © 2005 – 2008 Hayder Radha their intrinsic natural form. Therefore, we need to transform the signal to a format that is suitable for compression. ± Second, we compress the signal; this is usually accomplished through the process of quatization . ± Third, we need to code the quantized signal. This is done using entropy coding . Signal Compression 3 Copyright © 2005 – 2008 Hayder Radha Transform () yTx = x y Quantizer qQ y = q Encoder cC q = c The Channel Channel Coding Source Coding Signal Compression 4 Copyright © 2005 – 2008 Hayder Radha Inverse Transform 1 ˆˆ xTy = ˆ x ˆ y Dequantizer 1 ˆ yQq = q Decoder 1 qCc = c Source Decoding The Channel Channel Decoding
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Signal Compression 5 Copyright © 2005 – 2008 Hayder Radha Introduction to Transform Coding Transform coding is by far the most popular form of coding used for compressing multimedia content, and it is employed in a variety of applications, including communication and storage. This includes digital video services (digital cable, satellite, and terrestrial), standard- definition and high-definition television (HDTV), DVD, Signal Compression 6 Copyright © 2005 – 2008 Hayder Radha HD-DVD, Internet streaming, video conferencing, IPTV, etc. The vast majority of current multimedia standards, and in particular image and video coding standards, such as JEPG, JPEG2000, MPEG 1, MPEG 2, MPEG 4 1 , H.261, H.262 (MPEG 2), H.263, H.264, …. are based on transform coding. 1 What did happen to MPEG 3? Signal Compression 7 Copyright © 2005 – 2008 Hayder Radha The input to a Transform Coding (TC) encoder is, in general, a random sequence of symbols, which can be represented using a set of random variables: () 12 , ,..., n n X XX X = .
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SC_I_01_Intro_4 - Signal Compression 1 Signal Compression 2...

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