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Unified Speech and Audio Coding

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Title: Unified Speech and Audio Coding  
Author: World Heritage Encyclopedia
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Subject: MPEG-D, MPEG Surround, MPEG-1 Audio Layer I, Multiview Video Coding, ISO base media file format
Collection: Audio Codecs, Mpeg, Open Standards Covered by Patents
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Unified Speech and Audio Coding

Unified Speech and Audio Coding (USAC) is an ISO/IEC 23003-3 (a.k.a. MPEG-D Part 3)[2] and also as an MPEG-4 Audio Object Type in ISO/IEC 14496-3:2009/Amd 3 in 2012.[3]

It uses time-domain linear prediction and residual coding tools (ACELP-like techniques) for speech signal segments and transform coding tools (MDCT-based techniques) for music signal segments and it is able to switch between the tool sets dynamically in a signal-responsive manner. It is being developed with the aim of a single, unified coder with performance that equals or surpasses that of dedicated speech coders and dedicated music coders over a broad range of bitrates. Enhanced variations of the MPEG-4 Spectral Band Replication (SBR) and MPEG-D MPEG Surround parametric coding tools are integrated into the USAC codec.[4][5]

See also

Opus (codec) – a royalty free alternative, low latency codec for a similar usage


  1. ^ Fraunhofer Institute for Integrated Circuits. "Unified Speech and Audio Coding". Retrieved 2011-07-18. 
  2. ^ "ISO/IEC DIS 23003-3 - Information technology -- MPEG audio technologies -- Part 3: Unified speech and audio coding". 2011-02-15. Retrieved 2011-07-18. 
  3. ^ "ISO/IEC 14496-3:2009/PDAM 3 - Transport of unified speech and audio coding (USAC)". 2011-06-30. Retrieved 2011-07-18. 
  4. ^ MPEG. "Work Plan and Time Line". Retrieved 2011-07-18. 
  5. ^ "Unified Speech and Audio Coder Common Encoder Reference Software". March 2011. Retrieved 2011-07-18. 
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