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P.56 Speech Level Meter C5000 DSP Code
Description:
implements the ITU P.56 Speech Level Meter function (Method B). The P.56
function is intended primarily for speech level measurement. Over a time
interval, the algorithm obtains the active level of an irregular signal
such as speech by discerning and measuring in only the active signal periods.
In parallel, the long-term level is measured as the true RMS value of
the signal overall, irrespective of active and inactive signal periods.
A further result given by the process is the activity factor, that is
the proportion of the total active signal period to the total measurement
time.
With the assembler interface, the
software is in the form of three callable subroutines: one is for initialisation
where a user-set measurement time in samples is input, one is for processing
of each new sample, and one is for computing the results. If required,
the results routine can be called at any time prior to the expiry of the
set measurement time. Otherwise, the results are calculated automatically
at the end of the set time. Further calls of the main per-sample routine
cause the process to be repeated. The sample rate can be 8kHz, 9.6kHz,
or 16kHz.
The user is responsible for sample
input and for accepting the three results: long-term level, active level,
and activity factor. The software can be operated in a multi-channel mode:
a pointer is set to each per-channel block of memory at each sub-routine
call. By making multiple sub-routine calls, the code can be operated on
blocks of samples. The code is load-balanced so that, except when the
results are computed, there is no MIPS variation per sample. A C-callable
wrapper file can also be provided, allowing individual channels to be
called from C for processing of multiple sample blocks. A comprehensive
user's guide is provided with the code.
Performance:
| Measurement time range: | To 74 hours (8ksam/s) in sample periods |
| Dynamic range: | 68dB |
| Resolution/accuracy*: | 0.1dB in level measurement, 0.1% in activity factor |
- *activity-related results accuracies are subject to the P.56 measurement process
Processor Load:
| MIPS# | Data memory (words) | Prog memory (words)# |
| 0.63 | 58(per channel) | 0.35k |
- #figures are for TMS320C54x operation with the assembler interface at 8kHz sample rate
Availability: NOW - sale is under licence - integration support offered
