1 files changed, 98 insertions, 0 deletions
diff --git a/arm-fm-22k/lib_src/eas_pan.c b/arm-fm-22k/lib_src/eas_pan.c
new file mode 100644
index 0000000..373d90e
--- /dev/null
+++ b/arm-fm-22k/lib_src/eas_pan.c
@@ -0,0 +1,98 @@
+/*----------------------------------------------------------------------------
+ *
+ * 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;
+}
+