1 files changed, 84 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/audio_coding/codecs/ilbc/get_lsp_poly.c b/third_party/libwebrtc/modules/audio_coding/codecs/ilbc/get_lsp_poly.c
new file mode 100644
index 0000000000..e0fb21caf0
--- /dev/null
+++ b/third_party/libwebrtc/modules/audio_coding/codecs/ilbc/get_lsp_poly.c
@@ -0,0 +1,84 @@
+/*
+ *  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.
+ */
+
+/******************************************************************
+
+ iLBC Speech Coder ANSI-C Source Code
+
+ WebRtcIlbcfix_GetLspPoly.c
+
+******************************************************************/
+
+#include "modules/audio_coding/codecs/ilbc/get_lsp_poly.h"
+
+#include "modules/audio_coding/codecs/ilbc/defines.h"
+
+/*----------------------------------------------------------------*
+ * Construct the polynomials F1(z) and F2(z) from the LSP
+ * (Computations are done in Q24)
+ *
+ * The expansion is performed using the following recursion:
+ *
+ * f[0] = 1;
+ * tmp = -2.0 * lsp[0];
+ * f[1] = tmp;
+ * for (i=2; i<=5; i++) {
+ *    b = -2.0 * lsp[2*i-2];
+ *    f[i] = tmp*f[i-1] + 2.0*f[i-2];
+ *    for (j=i; j>=2; j--) {
+ *       f[j] = f[j] + tmp*f[j-1] + f[j-2];
+ *    }
+ *    f[i] = f[i] + tmp;
+ * }
+ *---------------------------------------------------------------*/
+
+void WebRtcIlbcfix_GetLspPoly(
+    int16_t *lsp, /* (i) LSP in Q15 */
+    int32_t *f)  /* (o) polonymial in Q24 */
+{
+  int32_t tmpW32;
+  int i, j;
+  int16_t high, low;
+  int16_t *lspPtr;
+  int32_t *fPtr;
+
+  lspPtr = lsp;
+  fPtr = f;
+  /* f[0] = 1.0 (Q24) */
+  (*fPtr) = (int32_t)16777216;
+  fPtr++;
+
+  (*fPtr) = WEBRTC_SPL_MUL((*lspPtr), -1024);
+  fPtr++;
+  lspPtr+=2;
+
+  for(i=2; i<=5; i++)
+  {
+    (*fPtr) = fPtr[-2];
+
+    for(j=i; j>1; j--)
+    {
+      /* Compute f[j] = f[j] + tmp*f[j-1] + f[j-2]; */
+      high = (int16_t)(fPtr[-1] >> 16);
+      low = (int16_t)((fPtr[-1] & 0xffff) >> 1);
+
+      tmpW32 = 4 * high * *lspPtr + 4 * ((low * *lspPtr) >> 15);
+
+      (*fPtr) += fPtr[-2];
+      (*fPtr) -= tmpW32;
+      fPtr--;
+    }
+    *fPtr -= *lspPtr * (1 << 10);
+
+    fPtr+=i;
+    lspPtr+=2;
+  }
+  return;
+}