The new Silence Compression Record (SCR) algorithm is based on energy detection and zero crossing. This SCR uses different parameters than the standard R4 SCR. Specifically, the "Pre-Compensation and "De-Glitch" parameters are no longer needed, and there are additional new parameters.
The SCR algorithm operates on one msec blocks of speech and uses a two-fold approach to determine whether a sample is speech or silence. Two Probability of Speech values are calculated using a zero crossing algorithm and an energy detection algorithm. These values are put together to calculate a Combined Probability of Speech.
The Energy Detection algorithm allows you to modify the background noise threshold range. Signals above the high threshold are declared Speech, and signals below the low threshold are declared silence.
Speech or silence is declared based on the previous sample, the current Combined Probability of Speech in relation to the Speech Probability Threshold and Silence Probability Threshold parameters and the Trailing Silence parameter.
See Table 7. Voice Board and Channel Parameters Supported for the parameters used with dx_setparm( ) to turn SCR ON/OFF. When enabled, voice record functions automatically record with SCR. For information on modifying SCR parameters, see the DM3 Configuration File Reference.
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