Reland "Avoiding overflow in cross correlation in NetEq."
The original CL is https://codereview.webrtc.org/1908623002/
An error was caused by that and this CL fix that problem and reland the CL.
BUG=
Review-Url: https://codereview.webrtc.org/1931933004
Cr-Commit-Position: refs/heads/master@{#12589}
diff --git a/webrtc/modules/audio_coding/neteq/cross_correlation.h b/webrtc/modules/audio_coding/neteq/cross_correlation.h
new file mode 100644
index 0000000..db14141
--- /dev/null
+++ b/webrtc/modules/audio_coding/neteq/cross_correlation.h
@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2016 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.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_CODING_NETEQ_CROSS_CORRELATION_H_
+#define WEBRTC_MODULES_AUDIO_CODING_NETEQ_CROSS_CORRELATION_H_
+
+#include "webrtc/common_types.h"
+
+namespace webrtc {
+
+// The function calculates the cross-correlation between two sequences
+// |sequence_1| and |sequence_2|. |sequence_1| is taken as reference, with
+// |sequence_1_length| as its length. |sequence_2| slides for the calculation of
+// cross-correlation. The result will be saved in |cross_correlation|.
+// |cross_correlation_length| correlation points are calculated.
+// The corresponding lag starts from 0, and increases with a step of
+// |cross_correlation_step|. The result is without normalization. To avoid
+// overflow, the result will be right shifted. The amount of shifts will be
+// returned.
+//
+// Input:
+// - sequence_1 : First sequence (reference).
+// - sequence_2 : Second sequence (sliding during calculation).
+// - sequence_1_length : Length of |sequence_1|.
+// - cross_correlation_length : Number of cross-correlations to calculate.
+// - cross_correlation_step : Step in the lag for the cross-correlation.
+//
+// Output:
+// - cross_correlation : The cross-correlation in Q(-right_shifts)
+//
+// Return:
+// Number of right shifts in cross_correlation.
+
+int CrossCorrelationWithAutoShift(const int16_t* sequence_1,
+ const int16_t* sequence_2,
+ size_t sequence_1_length,
+ size_t cross_correlation_length,
+ int cross_correlation_step,
+ int32_t* cross_correlation);
+
+} // namespace webrtc
+
+#endif // WEBRTC_MODULES_AUDIO_CODING_NETEQ_CROSS_CORRELATION_H_
