codec examples

Following is a list of popular speech, audio and video codecs. A codec is the circuit that performs the conversion from analog to digital or digital to digital (see codec).

Speech is a Subset of Audio

Audio codecs cover all sound whether spoken words or music. However, in order to create the most compressed digital data, speech codecs look for sound patterns commonly heard in a spoken language.

  SPEECH CODECS

  Name            Purpose

  A-Law           PCM telephone circuit (Europe)
  µ-Law           PCM telephone circuit (U.S.)
  DV Audio        MiniDV audio
  GSM 6.10        GSM cellphone
  G.711           A/V conferencing (ITU)
  G.722           A/V conferencing (ITU)
  G.723.1         VoIP, A/V conferencing (ITU)
  G.728           A/V conferencing (ITU)
  G.729           A/V conferencing (ITU)
  AMR-NB          GSM, 3GPP (ETSI narrowband)
  AMR-WB          GSM, 3GPP (ETSI wideband)
  ACELP.net       General speech (VoiceAge)
  ACELP.wide      High quality (VoiceAge)


  AUDIO CODECS

  Name            Purpose

  MP3             Music (MPEG)

  AAC             Music (MPEG)
  AAC Protected   Music (MPEG with DRM)

  WMA             Music (Windows)
  WMA Protected   Music (Windows with DRM)
  WMA Lossless    Music (Windows lossless)

  RA, RAM         Music (RealNetworks streaming)
  AIFF            Music (Macintosh)
  AU              Music (Sun)
  ACELP.live      Music (VoiceAge)
  Ogg Vorbis      Music (open source)
  FLAC            Music (open source lossless)
  Apple Lossless  Music (lossless)


  VIDEO CODECS

  Name            Purpose

  MPEG-1          Movies (MPEG)
  MPEG-2          Movies (MPEG)
  MPEG-4          Movies (MPEG)
  H.264           Movies (MPEG/ITU)

  VC-1            Movies (SMPTE)

  AVI             Movies (Windows)
  WMV             Movies/Streaming (Windows)
  RM, RV          Movies/Streaming (RealNetworks)
  Indeo           Movies (Intel)
  Cinepak         Movies (SuperMac Technologies)
  Sorenson        Movies (Sorenson Media)

  H.261           Videoconferencing (ITU)
  H.263           Videoconferencing (ITU)

Conversion and Compression

Compressing audio and video is a two-stage process. The first stage converts the signals from the source into an uncompressed digital format. At that point, one of several compression algorithms is used to further compress the digital code.

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