MPEG-4 Inside – Audio

MPEG-4 Inside – Audio

MPEG-4 Audio provides complete coverage of the bitrate range of 2 to 64 kbit/s. Good coded speech is obtained already at 2 kbit/s and transparent quality of monophonic music sampled at 48 kHz and 16 bits/sample is obtained at 64 kbit/s. Three classes of algorithms are used in the standard. The first covers the low bitrate range and has been designed to encode speech. The second can be used in the midrange to encode both speech and music. The third can be used in the high bitrate range and can be used for any audio signal.

MPEG-4 Audio contains a large set of coding tools through which it is possible to construct several audio and speech coding algorithms

  • MPEG-4 AAC, an extension of MPEG-2 AAC
  • Twin Vector Quantisation (VQ)
  • Speech coding based on Code Excited Linear Predictive (CELP) coding and on Parametric representation
  • Various usages of the Spatial Band Replication (SBR) technologies to provide high quality music at ever reduced bitrate, such as High Efficiency AAC (HE AAC)
  • Various forms of audio lossless coding.

 MPEG-4 AAC is MPEG-2 AAC with the addition of one tool: Perceptual Noise Substitution (PNS). This tool identifies and codes as random noise segments of spectral coefficients that appear to be noise-like. This is achieved by indicating that PNS is used and the value of the average power of the noise. A decoder uses a pseudo-random noise generator weighted by the signaled power value to reconstruct those coefficients.

AAC_general_model

Figure 1 – The MPEG-4 AAC encoder

The addition of Spectral Band Replication (SBR) MPEG-4 AAC has provided significant performance improvements. SBR consists of replicating the highband, i.e. the high frequency part of the spectrum. A small amount of data representing a parametric description of the highband is encoded and used in the decoding process. The data rate is by far below the data rate required when using conventional AAC coding of the highband.

SBR_model

Figure 2 – The SBR operating principle

A timeline of the development of the MPEG Audio standards is given in the figure below

AAC_timeline

Figure 3 – MPEG Audio development timeline

The MPEG-4 AA performance has been tested against a number of alternatives at different bitrates. the results are given in Figure 4.

MPEG-4_AAC_performance

Figure 4 – MPEG-4 AAC Verification Tests

48 thoughts on “MPEG-4 Inside – Audio

  1. Pingback: A Roadmap – Riding the Media Bits

  2. Pingback: datingnzcougar.info

  3. Pingback: free chat house wife sex live

  4. Pingback: see more

  5. Pingback: page address

  6. Pingback: link to a continuation

  7. Pingback: link to the page

  8. Pingback: check this out

  9. Pingback: visit the source

  10. Pingback: continued here

  11. Pingback: follow this link

  12. Pingback: find out more

  13. Pingback: 100% Free PORNO Hookup List 10328

  14. Pingback: 100% Free XXX Dates Users 76870

  15. Pingback: Best XXX Meet Users 94534

  16. Pingback: 100% Free Porn Dating Users 62640

  17. Pingback: FREE Sex Dates List 58190

  18. Pingback: FREE Porn Hookup Members 9883

  19. Pingback: Best Sex Hookup Members 30031

  20. Pingback: FREE XXX Dating Members 70764

  21. Pingback: FREE XXX Meet Members 9582

  22. Pingback: 100% Free Porn Hookup List 82467

  23. Pingback: 4f8399dedf47934722b63.com

  24. Pingback: go

  25. Pingback: notehub.org page w1Sg9I

  26. Pingback: notehub.org follow this address GKX

  27. Pingback: notehub.org read more 3qwC

  28. Pingback: more on this page

  29. Pingback: notehub.org

  30. Pingback: notehub.org i'll provide a link FCfDPV

  31. Pingback: notehub.org follow the link

  32. Pingback: based on these data

  33. Pingback: notehub.org

  34. Pingback: visit the source

  35. Pingback: notehub.org more information r81J

  36. Pingback: notehub.org continue

  37. Pingback: article source

  38. Pingback: read more

  39. Pingback: notehub.org click to to learn more

  40. Pingback: read more

  41. Pingback: a source

  42. Pingback: notehub.org

  43. Pingback: notehub.org page

  44. Pingback: notehub.org i provide a link

  45. Pingback: follow this address

  46. Pingback: notehub.org link to the page Ijx3lB

  47. Pingback: notehub.org

  48. Pingback: click at this page