Method and apparatus for coding a noise-suppressed audio signal
An unfiltered frame portion ( 2 ) from a second frame ( 503 ) is blended together with a filtered frame portion ( 1 ) from a first frame ( 501 ) to produce a combined frame portion ( 507 ). The combined frame portion ( 507 ) is then buffered ( 110 ) along with the filtered frame ( 501 ) for LPC analysis.
1. A method for creating noise-suppressed speech, the method comprising the steps of:
receiving a frame of speech plus noise data;
filtering the frame of speech plus noise data to produce a filtered frame;
weighting a portion of the frame of speech plus noise data to produce an increasing envelope portion of the speech plus noise frame;
weighting a portion of the filtered frame to produce a decreasing envelope portion of the filtered frame;
combining the decreasing envelope portion of the filtered frame with the increasing envelope portion of the speech plus noise frame to produce a combined portion; and
outputting noise-suppressed speech based on the filtered frame and the combined portion.
2. The method of claim 1 further comprising the step of:
performing linear predictive coding (LPC) on the noise suppressed speech.
3. The method of claim 1 wherein the step of filtering comprises the step of performing noise suppression on the frame of speech plus noise.
4. The method of claim 1 wherein the step of combining comprises the step of overlapping and adding the decreasing envelope portion of the filtered frame with the increasing envelope portion of the speech plus noise frame.
5. An apparatus for outputting linear prediction coefficients, the apparatus comprising:
a filter receiving a frame of speech plus noise data and filtering the frame of speech plus noise data to produce a filtered frame;
analysis circuitry weighting a portion of the frame of speech plus noise data to produce an increasing envelope portion of the speech plus noise frame;
synthesis circuitry weighting a portion of the filtered frame to produce a decreasing envelope portion of the filtered frame; and
a signal combiner combining the decreasing envelope portion of the filtered frame with the increasing envelope portion of the speech plus noise frame to produce a combined portion, and outputting noise-suppressed speech based on the filtered frame and the combined portion.
6. The apparatus of claim 5 further comprising:
a linear predictive coding (LPC) analyzer having the noise-suppressed speech as an input.