1 files changed, 135 insertions, 0 deletions
diff --git a/src/common_audio/signal_processing_library/main/source/resample_by_2.c b/src/common_audio/signal_processing_library/main/source/resample_by_2.c
new file mode 100644
index 0000000000..7ed4cfde09
--- /dev/null
+++ b/src/common_audio/signal_processing_library/main/source/resample_by_2.c
@@ -0,0 +1,135 @@
+/*
+ *  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 resampling by two functions.
+ * The description header can be found in signal_processing_library.h
+ *
+ */
+
+#include "signal_processing_library.h"
+
+// allpass filter coefficients.
+static const WebRtc_UWord16 kResampleAllpass1[3] = {3284, 24441, 49528};
+static const WebRtc_UWord16 kResampleAllpass2[3] = {12199, 37471, 60255};
+
+// decimator
+void WebRtcSpl_DownsampleBy2(const WebRtc_Word16* in, const WebRtc_Word16 len,
+                             WebRtc_Word16* out, WebRtc_Word32* filtState)
+{
+    const WebRtc_Word16 *inptr;
+    WebRtc_Word16 *outptr;
+    WebRtc_Word32 *state;
+    WebRtc_Word32 tmp1, tmp2, diff, in32, out32;
+    WebRtc_Word16 i;
+
+    // local versions of pointers to input and output arrays
+    inptr = in; // input array
+    outptr = out; // output array (of length len/2)
+    state = filtState; // filter state array; length = 8
+
+    for (i = (len >> 1); i > 0; i--)
+    {
+        // lower allpass filter
+        in32 = (WebRtc_Word32)(*inptr++) << 10;
+        diff = in32 - state[1];
+        tmp1 = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass2[0], diff, state[0] );
+        state[0] = in32;
+        diff = tmp1 - state[2];
+        tmp2 = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass2[1], diff, state[1] );
+        state[1] = tmp1;
+        diff = tmp2 - state[3];
+        state[3] = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass2[2], diff, state[2] );
+        state[2] = tmp2;
+
+        // upper allpass filter
+        in32 = (WebRtc_Word32)(*inptr++) << 10;
+        diff = in32 - state[5];
+        tmp1 = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass1[0], diff, state[4] );
+        state[4] = in32;
+        diff = tmp1 - state[6];
+        tmp2 = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass1[1], diff, state[5] );
+        state[5] = tmp1;
+        diff = tmp2 - state[7];
+        state[7] = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass1[2], diff, state[6] );
+        state[6] = tmp2;
+
+        // add two allpass outputs, divide by two and round
+        out32 = (state[3] + state[7] + 1024) >> 11;
+
+        // limit amplitude to prevent wrap-around, and write to output array
+        if (out32 > 32767)
+            *outptr++ = 32767;
+        else if (out32 < -32768)
+            *outptr++ = -32768;
+        else
+            *outptr++ = (WebRtc_Word16)out32;
+    }
+}
+
+void WebRtcSpl_UpsampleBy2(const WebRtc_Word16* in, WebRtc_Word16 len, WebRtc_Word16* out,
+                           WebRtc_Word32* filtState)
+{
+    const WebRtc_Word16 *inptr;
+    WebRtc_Word16 *outptr;
+    WebRtc_Word32 *state;
+    WebRtc_Word32 tmp1, tmp2, diff, in32, out32;
+    WebRtc_Word16 i;
+
+    // local versions of pointers to input and output arrays
+    inptr = in; // input array
+    outptr = out; // output array (of length len*2)
+    state = filtState; // filter state array; length = 8
+
+    for (i = len; i > 0; i--)
+    {
+        // lower allpass filter
+        in32 = (WebRtc_Word32)(*inptr++) << 10;
+        diff = in32 - state[1];
+        tmp1 = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass1[0], diff, state[0] );
+        state[0] = in32;
+        diff = tmp1 - state[2];
+        tmp2 = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass1[1], diff, state[1] );
+        state[1] = tmp1;
+        diff = tmp2 - state[3];
+        state[3] = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass1[2], diff, state[2] );
+        state[2] = tmp2;
+
+        // round; limit amplitude to prevent wrap-around; write to output array
+        out32 = (state[3] + 512) >> 10;
+        if (out32 > 32767)
+            *outptr++ = 32767;
+        else if (out32 < -32768)
+            *outptr++ = -32768;
+        else
+            *outptr++ = (WebRtc_Word16)out32;
+
+        // upper allpass filter
+        diff = in32 - state[5];
+        tmp1 = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass2[0], diff, state[4] );
+        state[4] = in32;
+        diff = tmp1 - state[6];
+        tmp2 = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass2[1], diff, state[5] );
+        state[5] = tmp1;
+        diff = tmp2 - state[7];
+        state[7] = WEBRTC_SPL_SCALEDIFF32( kResampleAllpass2[2], diff, state[6] );
+        state[6] = tmp2;
+
+        // round; limit amplitude to prevent wrap-around; write to output array
+        out32 = (state[7] + 512) >> 10;
+        if (out32 > 32767)
+            *outptr++ = 32767;
+        else if (out32 < -32768)
+            *outptr++ = -32768;
+        else
+            *outptr++ = (WebRtc_Word16)out32;
+    }
+}