1 files changed, 96 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/audio_coding/codecs/ilbc/simple_lpc_analysis.c b/third_party/libwebrtc/modules/audio_coding/codecs/ilbc/simple_lpc_analysis.c
new file mode 100644
index 0000000000..fdc4553d95
--- /dev/null
+++ b/third_party/libwebrtc/modules/audio_coding/codecs/ilbc/simple_lpc_analysis.c
@@ -0,0 +1,96 @@
+/*
+ *  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_SimpleLpcAnalysis.c
+
+******************************************************************/
+
+#include "modules/audio_coding/codecs/ilbc/simple_lpc_analysis.h"
+
+#include "modules/audio_coding/codecs/ilbc/bw_expand.h"
+#include "modules/audio_coding/codecs/ilbc/constants.h"
+#include "modules/audio_coding/codecs/ilbc/defines.h"
+#include "modules/audio_coding/codecs/ilbc/poly_to_lsf.h"
+#include "modules/audio_coding/codecs/ilbc/window32_w32.h"
+
+/*----------------------------------------------------------------*
+ *  lpc analysis (subrutine to LPCencode)
+ *---------------------------------------------------------------*/
+
+void WebRtcIlbcfix_SimpleLpcAnalysis(
+    int16_t *lsf,   /* (o) lsf coefficients */
+    int16_t *data,   /* (i) new block of speech */
+    IlbcEncoder *iLBCenc_inst
+    /* (i/o) the encoder state structure */
+                                     ) {
+  int k;
+  int scale;
+  size_t is;
+  int16_t stability;
+  /* Stack based */
+  int16_t A[LPC_FILTERORDER + 1];
+  int32_t R[LPC_FILTERORDER + 1];
+  int16_t windowedData[BLOCKL_MAX];
+  int16_t rc[LPC_FILTERORDER];
+
+  is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
+  WEBRTC_SPL_MEMCPY_W16(iLBCenc_inst->lpc_buffer+is,data,iLBCenc_inst->blockl);
+
+  /* No lookahead, last window is asymmetric */
+
+  for (k = 0; k < iLBCenc_inst->lpc_n; k++) {
+
+    is = LPC_LOOKBACK;
+
+    if (k < (iLBCenc_inst->lpc_n - 1)) {
+
+      /* Hanning table WebRtcIlbcfix_kLpcWin[] is in Q15-domain so the output is right-shifted 15 */
+      WebRtcSpl_ElementwiseVectorMult(windowedData, iLBCenc_inst->lpc_buffer, WebRtcIlbcfix_kLpcWin, BLOCKL_MAX, 15);
+    } else {
+
+      /* Hanning table WebRtcIlbcfix_kLpcAsymWin[] is in Q15-domain so the output is right-shifted 15 */
+      WebRtcSpl_ElementwiseVectorMult(windowedData, iLBCenc_inst->lpc_buffer+is, WebRtcIlbcfix_kLpcAsymWin, BLOCKL_MAX, 15);
+    }
+
+    /* Compute autocorrelation */
+    WebRtcSpl_AutoCorrelation(windowedData, BLOCKL_MAX, LPC_FILTERORDER, R, &scale);
+
+    /* Window autocorrelation vector */
+    WebRtcIlbcfix_Window32W32(R, R, WebRtcIlbcfix_kLpcLagWin, LPC_FILTERORDER + 1 );
+
+    /* Calculate the A coefficients from the Autocorrelation using Levinson Durbin algorithm */
+    stability=WebRtcSpl_LevinsonDurbin(R, A, rc, LPC_FILTERORDER);
+
+    /*
+       Set the filter to {1.0, 0.0, 0.0,...} if filter from Levinson Durbin algorithm is unstable
+       This should basically never happen...
+    */
+    if (stability!=1) {
+      A[0]=4096;
+      WebRtcSpl_MemSetW16(&A[1], 0, LPC_FILTERORDER);
+    }
+
+    /* Bandwidth expand the filter coefficients */
+    WebRtcIlbcfix_BwExpand(A, A, (int16_t*)WebRtcIlbcfix_kLpcChirpSyntDenum, LPC_FILTERORDER+1);
+
+    /* Convert from A to LSF representation */
+    WebRtcIlbcfix_Poly2Lsf(lsf + k*LPC_FILTERORDER, A);
+  }
+
+  is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
+  WEBRTC_SPL_MEMCPY_W16(iLBCenc_inst->lpc_buffer,
+                        iLBCenc_inst->lpc_buffer+LPC_LOOKBACK+BLOCKL_MAX-is, is);
+
+  return;
+}