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Mengubah Media Menjadi Bit Digital DIGITALISASI MEDIA.

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Presentasi berjudul: "Mengubah Media Menjadi Bit Digital DIGITALISASI MEDIA."— Transcript presentasi:


2 Mengubah Media Menjadi Bit Digital DIGITALISASI MEDIA

3 Representasi Digital “The power of multimedia systems originates in their ability to represent disparate information as a bit stream … every form of representation, from video to text, can be stored, processed and communicated using the same device: a computer.” Jain (1994), IEEE Multimedia vol. 1(2), p.3

4 Representasi Digital •Kekuatan dari sistem multimedia adalah pada kemampuan multimedia untuk merepresentasikan berbagai informasi yang berbeda dalam bentuk bit stream … semua bentuk representasi, dari video sampai teks, dapat disimpan, diproses dan dipertukarkan menggunakan divais yang sama yaitu komputer Jain (1994), IEEE Multimedia vol. 1(2), p.3

5 Multimedia: ART Joins BRAIN Merging of advanced digital and analog technology Digital Signal Processing Analog Signal Processing A/D D/A Analog or Real-World Signals Digital or Computer- World Signals Analog Domain Digital Domain Converter Technology Provides the Bridge [ICE 1997]

6 Digital Media System Diagram •A/D converter mengubah sinyal multimedia menjadi bit digital •Bit digital adalah representasi digital dari sinyal media •Enkoder kompresi mengurangi jumlah bit representasi tanpa menghilangkan konten media •Bitstream adalah bit digital kompak hasil kompresi •Dekoder kompresi merekonstruksi bit digital kembali dari bitstream •D/A converter mengubah bit digital menjadi sinyal multimedia

7 Digitisation •Dunia nyata (real world) adalah sistem analog kontinyu, sementara dunia digital (komputer) adalah digital diskrit. •Media analog perlu dirubah menjadi digital dengan perangkat untuk digitalisasi: scanner, digital-camera, dll •Media digital juga dapat dibuat langsung dengan komputer. •Perangkat display data digital : –Komputer; Digital TV; DVD / MP3 players; 3G / WAP phones, dll

8 Perangkat untuk Digitisasi •Teks: scanners & OCR .txt,.html… •Citra (Images): scanners; cameras; Photoshop .gif,.jpg… •Audio: microphones; MIDI devices .wav,.midi,.mp3… •Video: video cameras; capture cards; Premiere .mpg,.avi…

9 Digitisasi Teks Scanner + OCR Digital Text Handwriting recognizer

10 Digitisasi Image, Video & Audio

11 Karakteristik Media Digital •All data is now numeric: Images, video and sound is digitized into numbers. •Digital data can be processed in a computer into compressed formats. •Data is stored on disk (rather than VHS tapes or audio cassette •Data is transmitted digitally with additional information to help correct errors

12 Digital Disadvantages •Much more complex than analog systems •Much more raw data •Requires very high speed processing •More processing steps •Transmission data errors => serious damage

13 Overcome the problems •System complexity => most functions in software •Compress raw data => maths + software •High speed processing => digital technology •More processing steps => software + memory •data errors => corrected by maths + software •software => algoritma

14 Digital Advantages •Digital data not affected by processing •Compression => more data /channel •Processing costs: analog but digital •Complexity costs: analog but digital


16 Digitisation “rich variety of sensory inputs that make up images, text, moving pictures and sounds must be reduced to patterns of binary digits inside a computer” Chapman and Chapman (2000:34)


18 111010110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101000010000100100 000101000101010000100000011100101001001110101100001010100101000010100001000010010000010100010101000010000001110010100100111010 110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101000010000100100000101 000101010000100000011100101001001110101100001010100101000010100001000010010000010100010101000010000001110010100100111010110000 10101001010000101000010000100100000101000101010000100000011100101001001110101100001010100101000010100001000010010000010100010 101000010000001110010100100111010110000101010010100001010000100001001000001010001010100001000000111001010010111010110000101010 01010000101000010000100100000101000101010000100000011100101001110101100001010100101000010100001000010010000010100010101000010 000001110010100100111010110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000 101000010000100100000101000101010000100000011100101001001110101100001010100101000010100001000010010000010100010101000010000001 110010100100111010110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101000 010000100100000101000101010000100000011100101001001110101100001010100101000010100001000010010000010100010101000010000001110010 100100111010110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101000010000 100100000101000101010000100000011100101001011101011000010101001010000101000010000100100000101000101010000100000011100101001110 101100001010100101000010100001000010010000010100010101000010000001110010100100111010110000101010010100001010000100001001000001 010001010100001000000111001010010011101011000010101001010000101000010000100100000101000101010000100000011100101001001110101100 00101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101000010000100100000101000 101010000100000011100101001001110101100001010100101000010100001000010010000010100010101000010000001110010100100111010110000101 01001010000101000010000100100000101000101010000100000011100101001001110101100001010100101000010100001000010010000010100010101 000010000001110010100100111010110000101010010100001010000100001001000001010001010100001000000111001010010111010110000101010010 10000101000010000100100000101000101010000100000011100101001110101100001010100101000010100001000010010000010100010101000010000 001110010100100111010110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101 000010000100100000101000101010000100000011100101001001110101100001010100101000010100001000010010000010100010101000010000001110 010100100111010110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101000010 000100100000101000101010000100000011100101001001110101100001010100101000010100001000010010000010100010101000010000001110010100 100111010110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101000010000100 100000101000101010000100000011100101001011101011000010101001010000101000010000100100000101000101010000100000011100101001110101 10000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101000010000100100000101 000101010000100000011100101001001110101100001010100101000010100001000010010000010100010101000010000001110010100100111010110000 10101001010000101000010000100100000101000101010000100000011100101001001110101100001010100101000010100001000010010000010100010 101000010000001110010100100111010110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101 00101000010100001000010010000010100010101000010000001110010100100111010110000101010010100001010000100001001000001010001010100 001000000111001010010011101011000010101001010000101000010000100100000101000101010000100000011100101001011101011000010101001010 000101000010000100100000101000101010000100000011100101001110101100001010100101000010100001000010010000010100010101000010000001 110010100100111010110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101000 010000100100000101000101010000100000011100101001001110101100001010100101000010100001000010010000010100010101000010000001110010 100100111010110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101000010000 100100000101000101010000100000011100101001001110101100001010100101000010100001000010010000010100010101000010000001110010100100 111010110000101010010100001010000100001001000001010001010100001000000111001010010011101011000010101001010000101000010000100100 00010100010101000010000001110010100101110101100001010100101000010100001000010010000010100010101000010000001110010100

19 •Dua teknik dasar yang digunakan –PCM (Pulse Code Modulation) –DM (Delta Modulation) Analog voice signal Sampling clock PAM signal PCM signal Sampling Circuit Sampling Circuit Quantizer and compander Quantizer and compander Digitized voice signal Data Analog -> Sinyal Digital

20 •Blok diagram proses konversi bentuk gelombang analog ke data digital x a (t) x[n] x q [n] Continuous time Continuous amplitude Discrete time Continuous amplitude Discrete time Discrete (real) amplitude Sampling F s sampel/detik Kuantisasi N level/sampel Encoding c[n] B bits/sampel Discrete time Discrete (integer) amplitude N = 2 B Bit Rate = Fs. B bits/detik Pulse Code Modulation

21 Konsep Sinyal Analog t xa(t)xa(t) A Acos  A: Amplituda  : Frekuensi Radian F: Frekuensi Hertz  : Fasa

22 Konsep Sinyal Digital n x(n)x(n) A Acos  A: Amplituda  : Frekuensi Radian f: Frekuensi  : Fasa

23 Konversi Analog-Digital •Sampling, dengan F s = 1/T •Kuantisasi •Koding Sampling Kuantisasi Koding Sinyal analog Waktu Diskrit Nilai Diskrit Digital Filter

24 Sampling Sinyal Suara (Speech) •Teorema Sampling Nyquist –F s  2. F max •Untuk kualitas suara pada telepon –F s = 8 KHz 10002000300040000 dB 0 +10 -10 Hz A typical telephone transmission path

25 3.2 3.9 2.8 3.4 1.2 4.2 3 4 3 3 1 4 011100011 001100 Original signal PAM pulse PCM pulse with quantized error 011100011011001100 PCM output Pulse Code Modulation (PCM)

26 •Teorema sampling Nyquist menjamin sample data mengandung semua informasi dari sinyal orisinal •Frekuensi voice (speech) berada dibawah 4000Hz •Membutuhkan 8000 sample per detik •Sistem telepon dapat mendigitalisasi voice dengan 128 level atau 256 level. •Level-level tersebut disebut level kuantisasi –Jika128 level, maka bit tiap sampel = 7 bits (2 7 = 128). –Jika 256 level, maka bit tiap sampel = 8 bits (2 8 = 256). –8000 samples/sec x 7 bits/sample = 56Kbps for a single voice channel. –8000 samples/sec x 8 bits/sample = 64Kbps for a single voice channel. Pulse Code Modulation (PCM)

27 •PCM menggunakan pengkodean kuantisasi non-linear: spasi amplituda dari tiap level tidak linear –Ada step kuantisasi yang lebih banyak pada amplituda rendah (low) –Ini untuk mengurangi distorsi sinyal secara overall. –Tetapi menghasilkan quantizing error (or noise). Pulse Code Modulation (PCM)

28 Nonlinear encoding 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Strong signal Weak signal 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Quantizing level Without nonlinear encodingWith nonlinear encoding

29 Delta Modulation (DM) •Pada Delta Modulation, sinyal analog ditracking. •Analog input diaproksimasi dengan staircase function •Apakah Move up (naik) atau down (turun) satu level (  ) pada tiap interval sampel •Bit 1 digunakan untuk merepresentasi kenaikan level tegangan pd sinyal, dan bit 0 untuk merepresentasi turunnya level tegangan. -> Output dari DM adalah bit tunggal •Digunakan juga pada berbagai teknik Kompresi Data –e.g. Interframe coding techniques for video

30 Aplikasi Pada Ucapan Digital •Sinyal suara manusia (speech) dari mikropon –di filter (anti aliasing) 300Hz – 3300 Hz –disampling 8000 sample per detik –resolusi kuantisasi 8 bit per sample. •Hasilnya sbb: –Kebutuhan laju bit: 8000 x 8 = 64 kbps –Kualitas: SNR sekitar 48 dB

31 Aplikasi Pada Audio / Musik •Sinyal audio dari sumber audio (microphone, audio out) –di filter (anti aliasing) 0Hz – 20000 Hz –disampling 44100 sample per detik –resolusi kuantisasi 16 bit per sample –Dilakukan pada dua kanal L-R stereo •Hasilnya sbb: –Kebutuhan laju bit: 44100 x 16 x 2 = 1,411,200 bps = sekitar 1.4 Mbps –Kualitas: SNR sekitar 96 dB


33 Raw Digital Audio •AUDIO: a sequence of microphone readings on several channels. •Readings (samples) are normally taken at 11000, 22K or 44K per second and may be 8, 12 or 16-bit values. •Q: Berapa banyak memori dibutuhkan untuk menyimpan rekaman audio selama 5 menit dengan menggunakan 2 channel dan 16 bit per sample?

34 Raw Digital Audio.. KB = 1024 bytes MB = 1,048,576 bytesGB = 1,073,741,824 bytes Jika: Fs = 11000 Hz •N sampel = 5 (menit) x 60 (detik/menit) x 11000 (sampel/detik) = 3.300.000 sampel •N bit = 16 (bit/sampel) x 3.300.000 sampel = 52.800.000 bit = 6.600.000 byte = 6,295 MB •N bit Stereo (2 channel) = 6,295 MB x 2 ≈ 12,6 MB Jika: Fs = 44100 Hz •N sampel = 5 (menit) x 60 (detik/menit) x 44100 (sampel/detik) = 13.230.000 sampel •N bit = 16 (bit/sampel) x 13.230.000 sampel = 211.680.000 bit = 26.460.000 byte ≈ 25,234 MB •N bit Stereo = 25,234 MB x 2 ≈ 50,468 MB  satu lagu pada CD audio

35 Raw Digital Audio.. •Makin besar FS, makin baik kualitas rekaman audio, makin banyak jumlah bit yang dibutuhkan! •Makin besar jumlah bit / sampel, makin baik kualitas rekaman audio, makin banyak jumlah bit yang dibutuhkan!, demikian pula sebaliknya •Kualitas Audio Digital adalah linear dengan kebutuhan memori!

36 Jika sebuah lagu pada CD Audio ≈ 50 MB, sementara lagu yang sama dengan format MP3 ≈ 5 MB TANYA KENAPA?

37 Citra Digital •Berbeda dengan ucapan dan musik, sinyal gambar dikenal sebagai sinyal intensitas dua dimensi. Size: 300x400, 24 bpp colour, BMP: 360.000 byte; JPG:49.504 byte

38 Raw Digital Images •A raw camera image is an array of colored dots (pixels). An RGB image has 3 color components: RED, GREEN, BLUE •The image size is the total number of pixels. Q: what is the size of an image of 320 x 240 pixels? •The pixel value is made from 3 numbers being the amount (intensity) of each RGB color component (normally 8 bits). The image file size is the total number of bytes of pixel data Q: what is the file size of an RGB image of 320x240 pixels? (assume RGB pixels are 3x8 = 24-bit color) •We can alter the image by changing the pixel values

39 Sampling Citra Digital

40 Sinyal Video Digital •Sinyal video digital adalah kumpulan citra digital (disebut frame) yang di ‘tayangkan’ secara berurut menurut indeks waktu. Time Index 1 3579 Time Index 11

41 Raw Digital Video •VIDEO: a timed sequence of images (eg 25 frames/sec) Raw video data consists of RGB images. •Q: What is the data rate of RGB video at 25 frames/sec. Each frame being 320x240 pixels? (assume 24 bit color) •Q: How much video time (secs) can be stored on a 4 gigabyte disk? •It should be clear why we need compress video for transmission.

42 Sinyal Video Digital

43 Pengaruh Frame Per Detik •Semakin banyak fps, semakin mulus transisi gerak, sehingga gambar semakin ‘hidup’. Tetapi akibatnya semakin besar jumlah bit yang diperlukan. •Tipikal jumlah frame per detik (fps) adalah 5 fps, 30 fps, dan 60 fps, untuk videophone, TV, dan HDTV fpsDimMbps 5256 x 256 24 bpp 7.8 25256 x 256 24 bpp 39.3 30256 x 256 24 bpp 47.2 60256 x 256 24 bpp 94.4


45 Levels of Abstraction: a simple view •Multimedia information needs to be dealt with at different levels of abstraction, e.g.: –In terms of bit-streams for digitisation, compression, transmission, display, etc. –In terms of its content for intuitive retrieval and browsing

46 Levels of abstraction Meanings… Scenes Actions Movements People / Objects Regions (colour, shape, texture, motion) Pixels Electronic bits

47 What is Content? “every symbolic object consists of two interacting components, one of which is situated on the plane of expression while the other is situated on the plane of content”  “difference between what constitutes the objects themselves (media objects) and what is actually being communicated” Smoliar and Wilcox (1997)

48 Multimedia Content •Digital multimedia means that multimedia information can be created, retrieved, presented and interacted with in new ways BUT… •Computers don’t understand the content of multimedia items in the same way humans do…

49 Metadata •Metadata = “data about data” •In this case, data about the bit-streams that are texts, images, video, audio,etc. •By including metadata then multimedia applications can ‘know’ about media content, as well as about other things like who owns it, when it was made, who made it, etc. •BUT – there is a cost associated with manually produced metadata; need to consider potential for automation

50 RANGKUMAN •Media analog dirubah ke bentuk digital agar dapat disimpan,diproses dan dipertukarkan dengan bantuan komputer •Raw data digital berukuran sangat besar sehingga perlu dilakukan kompresi •Media (file) digital mempunyai meta- data agar komputer dapat mengenali konten-nya

51 TUGAS 1.Cari sebuah format file multimedia (image, audio, video, dll) kemudian: a)Temukan berapa ukuran Header File b)Bagaimana Struktur Header c)Temukan informasi meta data apa saja yang ada pada header tersebut d)Bagaimana struktur penyimpanan konten media pada format file tersebut 2.Jelaskan apa perbedaan tag header metadata IDv1 dan IDv2 dari format MP3

52 TUGAS 3.Buat sebuah gambar dengan Windows Paint (BMP) dengan resolusi tertentu, hitung berapa kebutuhan jumlah bit- nya, buktikan dengan ukuran file yang terjadi 4.Rekam suara/audio dengan Sound Recorder (WAV) selama beberapa detik (maks 10 detik), hitung kebutuhan jumlah bit-nya, buktikan dengan ukuran file yang terjadi

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