(DSP: Digital Signal Processing)

Contents

(compression) . Source Coding . . (symbol)

( ) ()

(Statistical Redundency) - (Huffman) (VLC, RLC) - (VLC) - (RLC) - Text WinZip

VLC : Variable Length Coding, () RLC : Run Length Coding, WinZip is a file archiver and compressor for Microsoft Windows, developed by WinZip Computing (formerly Nico Mak Computing).

( ) - (difference) - - DPCM, MC

DPCM : Differential Pulse Code Modulation MC : Motion Compensation

() - . - . - . - DCT, , Masking DCT : Discrete Cosine Transform, , . , .

(Voice) : 1972 64kbps PCM (Pulse Code Modulation) : 1974 32kbps ADPCM (Adaptive Differential PCM) : 1992 16kbps LDCELP (Low Delay Code Excited Linear Prediction) (Audio) : 1984 : 1992 MPEG-1 (Audio Layer 1, 2, 3) : 1994 MPEG-2 Audio (5.1CH , )

: FAX (Group 3, 4) : 1992 JPEG (Color ) : 1984 PCM : 1992 H.261 : 1992 MPEG-1 (CD 1.44Mbps) : 1994 MPEG-2 (H.262) - Redundancy - Correlation - (data ) - (6MHz) - Low Level Energy H.261 is a 1990 ITU-T video coding standard originally designed for transmission over ISDN lines on which data rates are multiples of 64 kbit/s. H.262 is an ITU-T digital video coding standard.

PCM / DPCM / ADPCMPCM (Pulse Code Modulation): DPCM (Differential PCM): ADPCM (Adaptive Differential PCM): ,

Coding

PCMPCM : Pulse Code Modulation, (, ) (discrete) 1937 A. H. Reeves

PCM : PCM

PCM

PCM

PCM

D/A

PCM (analog digital analog)

PCM

(Filtering)

(sampling) : PAM (Pulse Amplitude Modulation)

: Exact reconstruction of a continuous-time baseband signal from its samples is possible if the signal is bandlimited and the sampling frequency is greater than twice the signal bandwidth. Ts (1/2fm)

: (wave filter)

(quantization) : (PAM ),

(quantization noise) NQ = Q( ) S()

(S/NQ : Signal to quantizing noise ratio) step 2 S/NQ 6dB

(S) (Q) (Quantization Noise) .

, (Compression, Expansion) - () : . ( PCM )

- : , . ,

(Logarithmic) (Compressor) , (Expander) (Companding) .

.

Coding, Encoding A/D , .

: ,

- Run Length - Huffman - Lempel-Ziv

- DCT - - : PCM, DPCM, ADPCM

(lossless) : - . - 2:1 3:1 . - . - WinZip

(lossy) : - . - . - JPEG, MPEG

Run Length Huffman Lempel-Ziv

Run Length (RL) Run Length (run) (length) AAAABBBBBCCCCCCCCDEEEE 4A5B8C1D4E 22 byte 10 byte ( = 22/10 = 2.2)

Huffman , .

Lempel-Ziv (LZ)

( ) JPEG, MPEG (decode) , . / , .

DCT

DCT JPEG( ) MPEG H.261( ) Discrete Cosine Transform (DCT) 2 (spatial domain) (frequency domain) . DCT , .

: : () , VLSI

DCT

(quantum) . , . (scalar) , (vector) . , 4 4 . 49 4 49 4 48 12 . (dictionary) .

4 4 4 . 49 4 49 4 48 12 .

4

. (predictive technique) .

PCM PCM (Pulse Code Modulation) (sampling) (quantization) . PCM PCM .

DPCM (differential pulse code modulation) (difference) , . . ADPCM DPCM ADPCM (Adaptive DPCM) . ADPCM . . . . ADPCM .

JPEGMPEG

JPEGJoint Photographic Experts Group JPEG .JPEG . JPEG 88 pixel (DCT) , ( ) Huffman code

MPEGMoving Picture Experts Group . (1988 ) JPEG , . MPEG .

PCM coding data . , memory . (HDTV 20 Mbps)

PCM bit/samplePCM bit rate4 kHz8 kHz8 bit64 kbps20 kHz40 kHz12 bit480 kbpsTV5 MHz10 MHz8 bit80 MbpsHDTV25 MHz50 MHz8 bit400 Mbps

MPEG : (space) , , (subsampling) (space) : RGB YIQ : (subsampling) : I Q

: : DPCM, ADPCM : DCT

(subsampling) : : DCT : (difference) : . .

MPEG-1MPEG-2MPEG-4MPEG-7 TV VTR CD-ROM 1.5Mbps TV, HDTV , TV : 20Mbps HDTV : 100Mbps, 64kbps Audio/Viedo Multimedia 1.5Mbps 3Mbps 4.8kbps~64kbpsCD , CD , , , , ATM, , CATV, , VOD, , TV, , , , , , ( ), ,

MPEG Audio Filter Bank : subband (MP: 32 band) model : mask model / : masking / Bit stream encoding : / + bit stream

MPEG-1Audio Layer 1MPEG-1Audio Layer 2MPEG-1Audio Layer 3(MP3)DolbyAC-2DolbyAC-3bit33 ~ 448kbps32 ~ 384kbps32 ~ 320kbpschannel 128 ~ 192kbpschannel 32 ~ 640kbpschannel 192kbpschannel 128kbpschannel 96kbpschannel 128kbps5.1 channel384kbps DABDVD/ISDN RadioInternet AudioHDTVCATV

/ / / 2006 / / / 2006 / / / 2002http://en.wikipedia.org/