Audio Note VINDICATOR Instrukcja Użytkownika Pobierz pdf (Strona 6)

Vocoder

 IMBE™ by DVSI is the P25 Vocoder

– Model-based like virtually all vocoders

 Optimized for Low Bit Rate Apps (< 4.8 kbps)

 Breakdown

– 20 ms frame (50 frames per second)

– 88 vocoder bits

– 56 error control bits (unequal protection)

– 48 signaling bits

– 192 bits x 50 frames/s = 9600 bps

 BER Estimator Used for Frame-by-Frame Decisions

– Smoothed estimator weighs past, present, future frames

– Has implications for performance metrics

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