NCRE 2.2.5&2.2.6

NCRE

2.2.5 Multimedia Technology

Focus: Multimedia Concepts and Applications

1. Multimedia refers to the ability of two or more simultaneous acquisition of media, technology integration processing operations, editing, storage, etc.

• nature:Integrated, interactiveDiversity, real-time

2. Multimedia Digital
   • Digitized sound [frequencies and amplitudes]
     computer system device input sound signal input through the sample (measured at a certain frequency analog signals, reducing the frequency of sound higher the better), quantization (the sampled signal converted to the corresponding values), coding (binary representation) to convert it into a digital signal, and then output via an output device.
     Formula: B = the amount of audio data sampling frequency of the sampling time s × quantization bits Hz × b × number of channels / 8
     File format: WAV, MP3, VOC, MPEG , MIDI
   • Digital images
     • Digital still images, quantized collection +
     • FIG point (the image into a plurality of small pixels, recording color information for each pixel) and vector (Videos a radius of 100 pixels ⚪)
     • Moving digitized images, the still image is a moving image playback speed n pieces per second, and when n> 25, the consecutive pictures are formed in the human eye
     • Image File Format

name	feature
BMP Bitmap	Windows uses image storage format, larger space
TIFF Tagged Image File	Binary file format used between applications and computer platforms to exchange files
GIF	Online Graphics Interchange for an image file format used to exchange
JPEG	Currently the highest compression rate
PDF	Contain both vector and bitmap formats, electronic document search and navigation features
PNG	Instead of GIF and TIFF
DXF	Vector format, most graphics software support this format

5. Video file formats

name	feature
AVI	Windows operating system in a standard format of digital video files
MOV	Developed by Apple, the film production industry, a common format, the screen image is higher than AVI
DV	Generally it refers to a device to capture and store video in digital format
ASF	Advanced Streaming Format, the advantage of including local or network playback, scalable media types, partial downloads and scalability
WMV	Microsoft launched video file format, Windows media player can play ASF, WMV

3. Multimedia data compression
   1. Lossless compression using the statistical redundancy of data compression, also known as reversible encoding
      features: low compression ratio, 2: 1 to 5: 1, is widely used in text data, programs, and important graphics and images (fingerprint images, medical images) compression
      JPEG standard for still image compression first international standard
      specifies the issues related to voice data and video image data of the MPEG standard
   2. Lossy compression, lossy compression, lossy, commonly used in the compressed audio, image and video
      compression coding method: predictive coding, transform coding, model-based coding, fractal coding and vector quantization coding
   3. Compare

Compression Type	advantage	Shortcoming
lossless compression	Well preserved information, easy conversion	Occupy a large space, the compression ratio is not high, the compression rate is relatively low
Lossy compression	Reduce the memory footprint, viewing on the screen does not have a negative image of the appearance of the image	With a high-resolution printer, the image was significantly impaired

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2.2.6 computer virus and its prevention

Focus: characteristics, classification, prevention

1. (1) preparation means a computer virus is a computer program or insertion ofdestroyComputer broken ring function or data, and can affect the computerSelf-replicatingA set of computer instructions or program code
   features: parasitic, destructive, infectious, latent, hidden

   (2) in accordance with the type of Infection

Types of	Infection
Boot sector viruses	Disk boot sector infection
File viruses	COM, EXE, DRV, BIN, OVL, SYS and other executable files
Hybrid virus	Boot + executable file
Macro viruses	Do not infect program, only infected DOC, DOT
Network Virus	Spread through Email, destroy specific file extensions

(3) Common symptoms of infection

• The number of disk file without cause increased
  memory space of the system significantly reduced,
  date / time of the file is modified to a recent date / time,
  length of the executable file the virus usually will be significantly increased,
  the program can run normally because of a sudden two out of memory can not be loaded,
  the program load time or execution time is significantly longer,
  frequent crashes or does not start properly,
  often some inexplicable anomalies or information on the display

2. Prevention
   is mainly spread by media and computer networks to store two ways to understand

• Improve system security, and enhance safety awareness, frequent replacement of computer systems commonly used passwords to control access to system resources
  to install anti-virus software, anti-virus and update the virus database regularly ^{wash their hands regularly}
  and timely vulnerability scanning system, repair system vulnerabilities ^{timely self-test, concerned about the physical condition}
  set your browser security settings ^{to develop good habits}
  to avoid strangers and use the remote capability, the application does not require all closed ^{to reduce unnecessary social}
  attention to the latest virus situation, to understand, to prevention, to treatment ^{as described}
  without opening strange suspicious files, web pages not enter suspicious unsafe ^{to eat suspicious biological}
  data resources for classification in the computer processing ^{of the isolation quarantine}