The adaptive multi-rate wideband codec: history and performance

Networking Applications for Embedded Systems

“…The application in the fist core implements the tasks of first group and the application in the second core may implements some simple tasks in the first group and the networking tasks (these tasks are less complex). This strategy was validated by implementing a voice-over IP system based on an adaptive multirate (AMR) codec (Redwan Salami et al, 2002). In the first group (tasks A) consider an AMR encoder and in the second group (task B) consider an AMR decoder, the setting of the codec rate and the packet processing that consists of receiving and transmitting packets over network using UDP protocol (Johan Sjöberg et al, 2002).…”

An Investigation into the Performance Enhancement and Salient Features of AMR-WB Speech Codec Used in GSM Communication

“…The AMR technology is based upon the Analysis-by-Synthesis (AbS) method of source coding. This method utilizes the linear prediction (LP) model and a perceptual distortion measure to reproduce only those characteristics of input speech that are determined to be most important [8]. The AMR codec employs Algebraic Code-Excited Linear Prediction (ACELP) method for speech analysis-by-synthesis.…”

“…The speech bandwidth is divided into two frequency bands: low frequency band (50-6400 Hz) and high frequency band (6400-7000 Hz). These frequency bands are coded separately to reduce the complexity and to allocate more bits to subjectively most important frequency range [8].…”

“…One bit per frame is used to determine low pass filter applied to past excitation. The pitch and codebook gains are jointly quantized using 7 bits per sub-frame [8].…”

Parametric mixing for centralized VoIP conferencing using ITU-T recommendation G.722.2

“…When evaluating speech coders it is important to take all those attributes in consideration. Table 2-1 includes some statistics for the most common speech coders [26], [27], [28], [29].…”