diff options
Diffstat (limited to 'protocols/Tlen/src/codec/gsm_preprocess.c')
| -rw-r--r-- | protocols/Tlen/src/codec/gsm_preprocess.c | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/protocols/Tlen/src/codec/gsm_preprocess.c b/protocols/Tlen/src/codec/gsm_preprocess.c new file mode 100644 index 0000000000..462b8e6c17 --- /dev/null +++ b/protocols/Tlen/src/codec/gsm_preprocess.c @@ -0,0 +1,103 @@ +/*
+
+Tlen Protocol Plugin for Miranda NG
+Copyright (C) 2004-2007 Piotr Piastucki
+
+This program is based on GSM 06.10 source code developed by
+Jutta Degener and Carsten Bormann,
+Copyright 1992, 1993, 1994 by Jutta Degener and Carsten Bormann,
+Technische Universitaet Berlin
+
+This program is free software; you can redistribute it and/or
+modify it under the terms of the GNU General Public License
+as published by the Free Software Foundation; either version 2
+of the License, or (at your option) any later version.
+
+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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+*/
+#include "gsm.h"
+#include <stdio.h>
+
+/* 4.2.0 .. 4.2.3 PREPROCESSING SECTION
+ *
+ * After A-law to linear conversion (or directly from the
+ * Ato D converter) the following scaling is assumed for
+ * input to the RPE-LTP algorithm:
+ *
+ *
+ * Where S is the sign bit, v a valid bit, and * a "don't care" bit.
+ * The original signal is called sop[..]
+ *
+ */
+
+
+void gsm_preprocessing( gsm_state *state, short *in, short *out)
+{
+ int z1 = state->z1;
+ int z2 = state->z2;
+ int mp = state->mp;
+ int so, s1;
+ int msp, lsp;
+
+ int k = 160;
+
+ while (k--) {
+ /* Downscaling of the input signal
+ * in: 0.1.....................12
+ * S.v.v.v.v.v.v.v.v.v.v.v.v.*.*.*
+ * out: 0.1................... 12
+ * S.S.v.v.v.v.v.v.v.v.v.v.v.v.0.0
+ */
+ so = (*in >> 3) << 2;
+ in++;
+ /* 4.2.2 Offset compensation
+ *
+ * This part implements a high-pass filter and requires extended
+ * arithmetic precision for the recursive part of this filter.
+ * The input of this procedure is the array so[0...159] and the
+ * output the array sof[ 0...159 ].
+ */
+ /* Compute the non-recursive part
+ */
+ s1 = (so - z1) << 15;
+ z1 = so;
+ msp = z2 >> 15;
+ lsp = z2 - (msp << 15);
+ s1 += ((lsp * 32735) + 16384) >> 15;
+ z2 = msp * 32735 + s1;
+ /* 4.2.3 Preemphasis
+ */
+ msp = (-28180 * mp + 16384) >> 15;
+ mp = (z2 + 16384) >> 15;
+ *out++ = mp + msp;
+ }
+ state->z1 = z1;
+ state->z2 = z2;
+ state->mp = mp;
+/*
+ printf("preprocessed: \n");
+ for (k=0;k<160;k++) {
+ printf("%7d ", out[k]);//((float)i_lpc[i])/32768.0f);
+ }
+ printf("\n");
+ */
+}
+
+void gsm_postprocessing( gsm_state *state, short *in, short *out)
+{
+ int k;
+ int msr = state->msr;
+ for (k = 160; k--; in++, out++) {
+ msr = *in + ((msr * 28180 + 16384) >>15); /* Deemphasis */
+ *out = (msr + msr ) & 0xFFF8; /* Truncation & Upscaling */
+ }
+ state->msr = msr;
+}
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