Initial Commit

common/embeddedaudiosynthesis/arm-fm-22k/lib_src/eas_pan.c

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+/*----------------------------------------------------------------------------
+ *
+ * File:
+ * eas_pan.c
+ *
+ * Contents and purpose:
+ * Calculates left and right gain multipliers based on a pan value from -63 to +63
+ *
+ * NOTES:
+ * The _CMX_PARSER and _MFI_PARSER preprocessor symbols determine
+ * whether the parser works for those particular file formats.
+ *
+ * Copyright Sonic Network Inc. 2005
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ *----------------------------------------------------------------------------
+ * Revision Control:
+ *   $Revision: 82 $
+ *   $Date: 2006-07-10 11:45:19 -0700 (Mon, 10 Jul 2006) $
+ *----------------------------------------------------------------------------
+*/
+
+#include "eas_pan.h"
+#include "eas_math.h"
+
+/*----------------------------------------------------------------------------
+ * EAS_CalcPanControl()
+ *----------------------------------------------------------------------------
+ * Purpose:
+ * Assign the left and right gain values corresponding to the given pan value.
+ *
+ * This routine uses sin/cos approximations for an equal power curve:
+ *
+ * sin(x) = (2-4*c)*x^2 + c + x
+ * cos(x) = (2-4*c)*x^2 + c - x
+ *
+ * where  c = 1/sqrt(2)
+ * using the a0 + x*(a1 + x*a2) approach
+ *
+ * Inputs:
+ * pan          - pan value (-63 to + 63)
+ *
+ * Outputs:
+ * pGainLeft    linear gain multiplier for left channel (15-bit fraction)
+ * pGainRight   linear gain multiplier for left channel (15-bit fraction)
+ *
+ * Side Effects:
+ *----------------------------------------------------------------------------
+*/
+void EAS_CalcPanControl (EAS_INT pan, EAS_I16 *pGainLeft, EAS_I16 *pGainRight)
+{
+    EAS_INT temp;
+    EAS_INT netAngle;
+
+    /* impose hard limit */
+    if (pan < -63)
+        netAngle = -63;
+    else if (pan > 63)
+        netAngle = 63;
+    else
+        netAngle = pan;
+
+    /*lint -e{701} <avoid multiply for performance reasons>*/
+    netAngle = netAngle << 8;
+
+    /* calculate sin */
+    temp = EG1_ONE + FMUL_15x15(COEFF_PAN_G2, netAngle);
+    temp = COEFF_PAN_G0 + FMUL_15x15(temp, netAngle);
+
+    if (temp > SYNTH_FULL_SCALE_EG1_GAIN)
+        temp = SYNTH_FULL_SCALE_EG1_GAIN;
+    else if (temp < 0)
+        temp = 0;
+
+    *pGainRight = (EAS_I16) temp;
+
+    /* calculate cos */
+    temp = -EG1_ONE + FMUL_15x15(COEFF_PAN_G2, netAngle);
+    temp = COEFF_PAN_G0 + FMUL_15x15(temp, netAngle);
+    if (temp > SYNTH_FULL_SCALE_EG1_GAIN)
+        temp = SYNTH_FULL_SCALE_EG1_GAIN;
+    else if (temp < 0)
+        temp = 0;
+
+    *pGainLeft = (EAS_I16) temp;
+}
+