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Data compression

Pengantar Multimedia. Data compression. Purpose. Transmission of images over channels with limited bandwidth Digital Cinema = 250 Mbit/s 90 minutes movie = 170GB space Computer tomography 700 MB / examination

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Data compression

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  1. Pengantar Multimedia Data compression

  2. Purpose • Transmission of images over channels with limited bandwidth • Digital Cinema = 250 Mbit/s • 90 minutes movie = 170GB space • Computer tomography • 700 MB / examination • Several countries ruled that examination data must be stored for at least 10 years.

  3. RLE • Run Length Encoding • Very simple • ABCCCCCCCCDEFGGGG = 17 byte • RLE = ABC8DEFG4 = 9 byte

  4. Huffman • Uses trie • Find each char freq. • STMIK AKAKOM = 12 byte (96bit) • S = 1; T = 1; M = 2; I = 1; K = 3; A = 2; O = 1; _ = 1 • K3 A2 M2 S1 T1 I1 O1 _1

  5. K = 00; A = 01; M = 100; S =101; T = 1100; I = 1101; O = 1110; _ = 1111

  6. S T M I K A K A K O M • 101 1100 100 1101 00 01 00 01 00 1110 100 • 31 bit • 31 / 96 = 32% compression • 68 saving K = 00; A = 01; M = 100; S =101; T = 1100; I = 1101; O = 1110; _ = 1111

  7. LZ 77 (Lempel Ziv ) • Look for sequences of characters appearing over and over again • Use Pointers • Teknik Informatika Sistem Informasi • < j , l > (j = jump, l = length) • Pointer usually 2 bytes (16 bit) information

  8. Teknik Informatika Sistem Informasi • = • Teknik Informatika Sistem <19,7>si • 8 bit + 8 bit = 256 jump + 256 length • Modification : 16 bits (00000000,00000000) • 12 bits + 4 bit • 12 bit jump (long jump, 214 = 4096 distance) • 4 bit length (24 = 16 length)

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