--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.3/spandsp-0.0.3/src/spandsp/time_scale.h	Fri Jun 25 16:00:21 2010 +0200
@@ -0,0 +1,98 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * time_scale.h - Time scaling for linear speech data
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2004 Steve Underwood
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id: time_scale.h,v 1.7 2006/10/24 13:45:28 steveu Exp $
+ */
+
+#if !defined(_TIME_SCALE_H_)
+#define _TIME_SCALE_H_
+
+/*! \page time_scale_page Time scaling speech
+\section time_scale_page_sec_1 What does it do?
+The time scaling module allows speech files to be played back at a
+different speed, from the speed at which they were recorded. If this
+were done by simply speeding up or slowing down replay, the pitch of
+the voice would change, and sound very odd. This modules keeps the pitch
+of the voice normal.
+
+\section time_scale_page_sec_2 How does it work?
+The time scaling module is based on the Pointer Interval Controlled
+OverLap and Add (PICOLA) method, developed by Morita Naotaka.
+Mikio Ikeda has an excellent web page on this subject at
+http://keizai.yokkaichi-u.ac.jp/~ikeda/research/picola.html
+There is also working code there. This implementation uses
+exactly the same algorithms, but the code is a complete rewrite.
+Mikio's code batch processes files. This version works incrementally
+on streams, and allows multiple streams to be processed concurrently.
+*/
+
+#define TIME_SCALE_MIN_PITCH    60
+#define TIME_SCALE_MAX_PITCH    250
+#define TIME_SCALE_BUF_LEN      (2*SAMPLE_RATE/TIME_SCALE_MIN_PITCH)
+
+typedef struct
+{
+    double rate;
+    double rcomp;
+    double rate_nudge;
+    int fill;
+    int lcp;
+    int16_t buf[TIME_SCALE_BUF_LEN];
+} time_scale_t;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*! Initialise a time scale context. This must be called before the first
+    use of the context, to initialise its contents.
+    \brief Initialise a time scale context.
+    \param s The time scale context.
+    \param rate The ratio between the output speed and the input speed.
+    \return 0 if initialised OK, else -1. */
+int time_scale_init(time_scale_t *s, float rate);
+
+/*! Change the time scale rate.
+    \brief Change the time scale rate.
+    \param s The time scale context.
+    \param rate The ratio between the output speed and the input speed.
+    \return 0 if changed OK, else -1. */
+int time_scale_rate(time_scale_t *s, float rate);
+
+/*! Time scale a chunk of audio samples.
+    \brief Time scale a chunk of audio samples.
+    \param s The time sclae context.
+    \param out The output audio sample buffer.
+    \param in The input audio sample buffer.
+    \param len The number of input samples.
+    \return The number of output samples.
+*/
+int time_scale(time_scale_t *s, int16_t out[], int16_t in[], int len);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+/*- End of file ------------------------------------------------------------*/