1 files changed, 92 insertions, 0 deletions
diff --git a/src/common_audio/signal_processing_library/main/source/filter_ar.c b/src/common_audio/signal_processing_library/main/source/filter_ar.c
new file mode 100644
index 0000000000..30a56c1c64
--- /dev/null
+++ b/src/common_audio/signal_processing_library/main/source/filter_ar.c
@@ -0,0 +1,92 @@
+/*
+ *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+
+/*
+ * This file contains the function WebRtcSpl_FilterAR().
+ * The description header can be found in signal_processing_library.h
+ *
+ */
+
+#include "signal_processing_library.h"
+
+int WebRtcSpl_FilterAR(G_CONST WebRtc_Word16* a,
+                       int a_length,
+                       G_CONST WebRtc_Word16* x,
+                       int x_length,
+                       WebRtc_Word16* state,
+                       int state_length,
+                       WebRtc_Word16* state_low,
+                       int state_low_length,
+                       WebRtc_Word16* filtered,
+                       WebRtc_Word16* filtered_low,
+                       int filtered_low_length)
+{
+    WebRtc_Word32 o;
+    WebRtc_Word32 oLOW;
+    int i, j, stop;
+    G_CONST WebRtc_Word16* x_ptr = &x[0];
+    WebRtc_Word16* filteredFINAL_ptr = filtered;
+    WebRtc_Word16* filteredFINAL_LOW_ptr = filtered_low;
+
+    state_low_length = state_low_length;
+    filtered_low_length = filtered_low_length;
+
+    for (i = 0; i < x_length; i++)
+    {
+        // Calculate filtered[i] and filtered_low[i]
+        G_CONST WebRtc_Word16* a_ptr = &a[1];
+        WebRtc_Word16* filtered_ptr = &filtered[i - 1];
+        WebRtc_Word16* filtered_low_ptr = &filtered_low[i - 1];
+        WebRtc_Word16* state_ptr = &state[state_length - 1];
+        WebRtc_Word16* state_low_ptr = &state_low[state_length - 1];
+
+        o = (WebRtc_Word32)(*x_ptr++) << 12;
+        oLOW = (WebRtc_Word32)0;
+
+        stop = (i < a_length) ? i + 1 : a_length;
+        for (j = 1; j < stop; j++)
+        {
+            o -= WEBRTC_SPL_MUL_16_16(*a_ptr, *filtered_ptr--);
+            oLOW -= WEBRTC_SPL_MUL_16_16(*a_ptr++, *filtered_low_ptr--);
+        }
+        for (j = i + 1; j < a_length; j++)
+        {
+            o -= WEBRTC_SPL_MUL_16_16(*a_ptr, *state_ptr--);
+            oLOW -= WEBRTC_SPL_MUL_16_16(*a_ptr++, *state_low_ptr--);
+        }
+
+        o += (oLOW >> 12);
+        *filteredFINAL_ptr = (WebRtc_Word16)((o + (WebRtc_Word32)2048) >> 12);
+        *filteredFINAL_LOW_ptr++ = (WebRtc_Word16)(o - ((WebRtc_Word32)(*filteredFINAL_ptr++)
+                << 12));
+    }
+
+    // Save the filter state
+    if (x_length >= state_length)
+    {
+        WebRtcSpl_CopyFromEndW16(filtered, x_length, a_length - 1, state);
+        WebRtcSpl_CopyFromEndW16(filtered_low, x_length, a_length - 1, state_low);
+    } else
+    {
+        for (i = 0; i < state_length - x_length; i++)
+        {
+            state[i] = state[i + x_length];
+            state_low[i] = state_low[i + x_length];
+        }
+        for (i = 0; i < x_length; i++)
+        {
+            state[state_length - x_length + i] = filtered[i];
+            state[state_length - x_length + i] = filtered_low[i];
+        }
+    }
+
+    return x_length;
+}