Data Preparation
A-3
Editing Tools and Data Preparation
A.2 Data Preparation
The MSP53C391 and MSP53C392 slave synthesizers support several algo-
rithms for speech synthesizing. The speech data sent to the slave device must
match the format defined by TI or generated from a TI tool (SDS3000 for MELP
or CELP and WINSDS for LPC). The data preparation for different algorithms
for MSP53C391 and MSP53C392 is discussed in the following paragraphs.
A.2.1 LPC
LPC is processed and editing using the WINSDS station. Please refer to the
WINSDS User’s Guide (literature number: SPSU010) for details.
A.2.2 MELP and CELP
The SDS3000 is used to convert an input audio data file into the MELP or
CELP data formats. The input data file can be either signed binary or .WAV for-
mat file. The audio data should be sampled at either 8 kHz or 10 kHz and
should have a precision of 16 bits.
The sound files should start and stop at a level close to zero, otherwise errors
may result. The volume of the sound files should also be adjusted to a level
with a peak-to-peak 0.5 to –0.5 (assume full scale is +1 to –1). When
the sound file is too loud after the encoding, clipping will result. Additionally,
if the wave file is sampled at a higher rate (CD quality sound file 44.1-kHz sam-
pling or DAT in 48-kHz), resampling to 8 kHz or 10 kHz is necessary for the
conversion. Filtering and renormalizing may be necessary during down-sam-
pling to reduce aliasing and noise.
There are a number of software programs available to do this resampling func-
tion. Two commonly available examples are GoldWave and Cool Edit.
GoldWave is a shareware program that provides editing function on sound
files in a Windows environment. This software can be downloaded from the
web: http://www.goldwave.com
By using the GoldWave sound editor, the sound file can be cut to eliminate the
leading and the following silence. The volume can also be adjusted.
To resample the original wave/sound file, we need to cut all the high-frequency
portion first to eliminate the error in resampling. All frequencies above one half
of the final sampling rate should be removed from the sound file. For example,
before converting the sampling rate to 8 kHz, the data should be filtered to re-
move all frequency components above 4 kHz.
GoldWave is a product of Goldwave Corporation
Cool Edit is a product of Syntrillium Software Corporation
Summary of Contents for MSP53C391
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