ADVANCES IN SOURCE-CONTROLLED VARIABLE BIT RATE WIDEBAND SPEECH CODING (original) (raw)

This paper presents novel techniques for source controlled variable rate wideband speech coding. These techniques have been used in the variable-rate multimode wideband (VMR-WB) speech codec recently selected by 3GPP2 for wideband (WB) speech telephony, streaming, and multimedia messaging services in the cdma2000 third generation wireless system. The coding algorithm contains several innovations that enable very good performance at average bit rates as low as 4.0 kbit/s in typical conversational operating conditions. These innovations include: Efficient noise suppression algorithm, signal classification and rate selection algorithm that enables high quality operation at low average bit rates, efficient post-processing techniques tailored for wideband signals, and novel frame erasure concealment techniques including supplementary information for reconstruction of lost onsets and improving decoder convergence. Further, the coder utilizes efficient coding types optimized for different classes of speech signal including a generic coding type based on AMR-WB for transients and onsets, voiced coding type optimized for stable voiced signals and utilizing novel signal modification procedure resulting in good wideband quality at 6.2 kbit/s, unvoiced coding types optimized for unvoiced segments, and efficient comfort noise generation coding. The article describes in detail some of the codec novel features.