What does SMV mean in Electronics?

Selectable Mode Vocoder

Selectable Mode Vocoder is variable bitrate speech coding standard used in CDMA2000 networks. SMV provides multiple modes of operation that are selected based on input speech characteristics. The SMV for Wideband CDMA is based on 4 codecs: full rate at 8.5 kbit/s, half rate at 4 kbit/s, quarter rate at 2 kbit/s, and eighth rate at 800 bit/s. The full rate and half rate are based on the CELP algorithm that is based on a combined closed-loop-open-loop-analysis. In SMV the signal frames are first classified as: Silence/Background noise Non-stationary unvoiced Stationary unvoiced Onset Non-stationary voiced Stationary voiced The algorithm includes voice activity detection followed by an elaborate frame classification scheme. Silence/background noise and stationary unvoiced frames are represented by spectrum-modulated noise and coded at 1/4 or 1/8 rate. The SMV uses 4 subframes for full rate and two/three subframes for half rate. The stochastic codebook structure is also elaborate and uses sub-codebooks each tuned for a particular type of speech. The sub-codebooks have different degrees of pulse sparseness. SMV scores a high of 3.6 MOS at full rate with clean speech.

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