More internet

More internet

1. Common file standards

   • JPG or JPEG
     • Joint photographic experts group
     • A compressed bitmap image file format commonly used for photographs
     • You can choose how much comoression you want
   • GIF
     • Graphics interchange format
     • Lossless bitmap image compression
     • Only suitable fro small images such as logos
     • A sequence of GIF images can be displayed to produce animations
   • PDF
     • Portable document format
     • Open standard fro exchanging documents
     • Text and graphics are displayed exactly as it was written
     • Many applications are capable of reading/creating them
   • MPEG
     • Moving pictures expert group
     • A set of standards designed to encode audio visual information
     • Uses lossy compression for both sound adn visual components
   • MP3
     • Moving pictures expert group audio layer 3
     • It is a de fecto standard fro distributing digital music files on the internet
     • MP3 uses lossy compression to reduce the file size to abour 1/10 of the original

2. Compression

   • Lossy
     • Removing some of the data from a file in order to reduce its size
     • For photographs
       • Reduction in colour depth
       • Reduction in resoution
     • Relies on the removal of data which is the least likely to be noticed by the human senses
     • After compression, it can't be restored
     • For audio
       • Reduction in the sample rate and sounds beyond the limits of most peoples hearing
   • Lossless
     • No information or data is lost
     • Data compressed into common parts so that it can be restored exactly
   • Reduction in filesize to reduce download times and storage requirements