From d1bf60771c411668c5b8c80a73538a312151fd24 Mon Sep 17 00:00:00 2001
From: Kenan Gillet <kenan.gillet@gmail.com>
Date: Sat, 18 Apr 2009 22:53:37 +0000
Subject: [PATCH] Add LP zero synthesis filter. Patch by Kenan Gillet.
Originally committed as revision 18616 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
libavcodec/celp_filters.c | 20 ++++++++++++++++++++
libavcodec/celp_filters.h | 22 ++++++++++++++++++++++
2 files changed, 42 insertions(+)
diff --git a/libavcodec/celp_filters.c b/libavcodec/celp_filters.c
index 2a6b0670b49..b2094a164a6 100644
--- a/libavcodec/celp_filters.c
+++ b/libavcodec/celp_filters.c
@@ -103,3 +103,23 @@ void ff_celp_lp_synthesis_filterf(
out[n] -= filter_coeffs[i-1] * out[n-i];
}
}
+
+void ff_celp_lp_zero_synthesis_filterf(
+ float *out,
+ const float* filter_coeffs,
+ const float* in,
+ int buffer_length,
+ int filter_length)
+{
+ int i,n;
+
+ // Avoids a +1 in the inner loop.
+ filter_length++;
+
+ for(n=0; n<buffer_length; n++)
+ {
+ out[n] = in[n];
+ for(i=1; i<filter_length; i++)
+ out[n] -= filter_coeffs[i-1] * in[n-i];
+ }
+}
diff --git a/libavcodec/celp_filters.h b/libavcodec/celp_filters.h
index d33aafd229c..4a9eb1c49b1 100644
--- a/libavcodec/celp_filters.h
+++ b/libavcodec/celp_filters.h
@@ -91,4 +91,26 @@ void ff_celp_lp_synthesis_filterf(
int buffer_length,
int filter_length);
+/**
+ * LP zero synthesis filter.
+ * @param out [out] pointer to output buffer
+ * @param filter_coeffs filter coefficients.
+ * @param in input signal
+ * - the array in[-filter_length, -1] must
+ * contain the previous input of this filter
+ * @param buffer_length amount of data to process
+ * @param filter_length filter length (10 for 10th order LP filter)
+ *
+ * @note Output buffer must contain filter_length samples of past
+ * speech data before pointer.
+ *
+ * Routine applies A(z) filter to given speech data.
+ */
+void ff_celp_lp_zero_synthesis_filterf(
+ float *out,
+ const float* filter_coeffs,
+ const float* in,
+ int buffer_length,
+ int filter_length);
+
#endif /* AVCODEC_CELP_FILTERS_H */
--
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