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File Compression Techniques

File Compression Techniques. Data Compression. abcde…. nR bits. abcde…. {. n uses. compress. decompress. Why data compression?. To reduce memory storage requirements. Faster technique ,so less transmission time and reducing bandwidth also.

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File Compression Techniques

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  1. File Compression Techniques

  2. Data Compression abcde… nR bits abcde… { n uses compress decompress

  3. Why data compression? • To reduce memory storage requirements. • Faster technique ,so less transmission time and reducing bandwidth also. • It reduces consumption of expensive resources such as hard disk space.

  4. How data compression is possible? • Compression is possible by removing usual redundancies or information that is often repeated. • By using various formats to store data. • By shrinking one or more files into a single file.

  5. IMAGE FORMATS JPEG • Joint Photographic Expert Group. • Lossy compression for photographic images. • 24 Bits/pixel. • Degradation of quality.

  6. BMP • Bitmap File Format for digital images. • Support 24 bits/pixel to store color information. • Device independent format. GIF • Graphic Interchange Format. • Supports 8 bits/pixel for color storage. • Lossy compression when colors of image > 256 • Lossless when colors < 256.

  7. AUDIO FORMATS MP3 • Moving Picture Expert Group Format for audio encoding. • Lossy compression. • Used on internet for downloading and uploading. • Quality of sound is still clear. • Works by reducing certain parts of audio.

  8. WAV • Waveform Audio File Format. • Compatible for only Microsoft and IBM O.S. • Quiet large files. • Lossless compression. WMA • Windows Media Audio File Format by Microsoft. • Lossless compression. • Competitor to MP3. • Basically meant for windows media player. • High compressing than Mp3.

  9. VIDEO FORMATS FLV • Flash Video File format. • Compatible with media flash players. • Better quality of video. • File size is small. • Users of this format are Hulu, Youtube, Google video etc.

  10. WMV • Windows Media Video Compression Format. • High definition video content. • Small in size. • Used in emails also. AVCHD • Advanced Video Coding High definition. • Basically ,playstations and video games have this file formats. • Provides good resolution video.

  11. Run LENGTH ENCODING • This method reduces the consecutive occurrences of a given symbol. • Real life example is fax machine. • Shows only one copy of symbol along with the count.

  12. Differential pulse code modulation In this method • First a reference symbol is placed. • Difference is placed between that symbol and reference symbol.

  13. DICTIONARY BASED ENCODING • Lempel- Ziv (LZ) Compression Algorithm. • Dictionary of variable length strings is built. • Contain every string expected to occur in data.

  14. AUDIO COMPRESSION PREDICTIVE ENCODING- • Differences between the samples are encoded. • Normally used for speech. PERCEPTUAL ENCODING- • Used to create cd quality audio. • Based on the science of psychoacoustics.

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