samer@0: /*
samer@0:  *	AudioSource.java	
samer@0:  *
samer@0:  *	Copyright (c) 2000, Samer Abdallah, King's College London.
samer@0:  *	All rights reserved.
samer@0:  *
samer@0:  *	This software is provided AS iS and WITHOUT ANY WARRANTY; 
samer@0:  *	without even the implied warranty of MERCHANTABILITY or 
samer@0:  *	FITNESS FOR A PARTICULAR PURPOSE.
samer@0:  */
samer@0: 
samer@0: package samer.audio;
samer@0: import samer.tools.*;
samer@0: 
samer@0: /**
samer@0: 	General interface for objects that can supply an
samer@0: 	audio stream.
samer@0: */
samer@0: 
samer@0: public interface AudioSource
samer@0: {
samer@0: 	boolean  isOpen();
samer@0: 	void open() throws Exception;
samer@0: 	void close();
samer@0: 	void dispose();
samer@0: 
samer@0: 	/** return a task which reads samples into the given buffer
samer@0: 	 *  The idea is that the audio source can choose the right
samer@0: 	 *  kind of reader depending on the format of the audio stream,
samer@0: 	 *  and then handle the conversion to doubles automatically
samer@0: 	 */
samer@0: 	Task reader(double buf[], int off, int len);
samer@0: 	Task reader(float buf[], int off, int len);
samer@0: 
samer@1: 	int getChannels();
samer@1: 	float getRate();
samer@1: 
samer@0: 	public static class Util {
samer@0: 		/* NB. These copying functions allow NEGATIVE offset (off<0). The semantics 
samer@0: 		 * of this is are that n values are copied from source to destination, writing 
samer@0: 		 * into the destination starting at the negative offset, but that values before
samer@0: 		 * index 0 will never be accessed, hence, they are not actually copied. Only
samer@0: 		 * the last n-off values will be available in dst starting from index 0.
samer@0: 		 * This is useful as it allows block-wise audio input where the block lenght
samer@0: 		 * is smaller than the step length.
samer@0: 		 */
samer@0: 
samer@0: 		public static void shortToDoubleMixDown(byte [] src, double [] dst, int off, int n, int m) {
samer@0: 			double a = (1.0/(m*32768.0)); // scaling factor including division by mixdown factor m
samer@0: 			int skip = off<0 ? -off : 0;
samer@0: 			for (int i=2*m*skip, j=off+skip; j<n+off; j++) {
samer@0: 				dst[j] = 0;
samer@0: 				for (int k=0; k<m; k++) dst[j] += a*((src[i++]&0xff) | src[i++]<<8);
samer@0: 			}
samer@0: 		}
samer@0: 
samer@1: 		public static void mediumToDouble(byte [] src, double [] dst, int off, int n) {
samer@1: 			int i, j;
samer@1: 			if (off<0) { i= 3*(-off); j=0; } else { i=0; j=off; }
samer@1: 			while (j<n+off) dst[j++] = (1.0/8388608.0)*((src[i++]&0xff) | src[i++]<<8 | src[i++]<<16);
samer@1: 		}
samer@1: 
samer@0: 		public static void shortToDouble(byte [] src, double [] dst, int off, int n) {
samer@0: 			int i, j;
samer@0: 			if (off<0) { i= 2*(-off); j=0; } else { i=0; j=off; }
samer@0: 			while (j<n+off) dst[j++] = (1.0/32768.0)*((src[i++]&0xff) | src[i++]<<8);
samer@0: 		}
samer@0: 
samer@0: 		public static void byteToDouble(byte [] src, double [] dst, int off, int n) {
samer@0: 			int i, j;
samer@0: 			if (off<0) { i= -off; j=0; } else { i=0; j=off; }
samer@0: 			while (j<n+off) dst[j++] = (1.0/256.0)*(src[i++]&0xff)-128.0;
samer@0: 		}
samer@0: 
samer@0: 		public static void shortToFloatMixDown(byte [] src, float [] dst, int off, int n, int m) {
samer@0: 			int skip = off<0 ? -off : 0;
samer@0: 			float a = (1F/(m*32768F)); // scaling factor including division by mixdown factor m
samer@0: 			for (int i=2*m*skip, j=off+skip; j<n+off; j++) {
samer@0: 				dst[j] = 0;
samer@0: 				for (int k=0; k<m; k++) dst[j] += a*((src[i++]&0xff) | src[i++]<<8);
samer@0: 			}
samer@0: 		}
samer@0: 
samer@0: 		public static void shortToFloat(byte [] src, float [] dst, int off, int n) {
samer@0: 			int i, j;
samer@0: 			if (off<0) { i= -2*off; j=0; } else { i=0; j=off; }
samer@0: 			while (j<n+off) dst[j++] = (1F/32768F)*((src[i++]&0xff) | src[i++]<<8);
samer@0: 		}
samer@0: 
samer@0: 		public static void byteToFloat(byte [] src, float [] dst, int off, int n) {
samer@0: 			int i, j;
samer@0: 			if (off<0) { i= -off; j=0; } else { i=0; j=off; }
samer@0: 			while (j<n+off) dst[j++] = (1F/256F)*(src[i++]&0xff)-128F;
samer@0: 		}
samer@0: 	}
samer@0: }
samer@0: