diff --git a/com/breakfastquay/rubberband/RubberBandStretcher.java b/com/breakfastquay/rubberband/RubberBandStretcher.java
index aa7e613..036516d 100644
--- a/com/breakfastquay/rubberband/RubberBandStretcher.java
+++ b/com/breakfastquay/rubberband/RubberBandStretcher.java
@@ -23,6 +23,9 @@
 
 package com.breakfastquay.rubberband;
 
+import java.util.Map;
+import java.util.Set;
+
 public class RubberBandStretcher
 {
     public RubberBandStretcher(int sampleRate, int channels,
@@ -62,6 +65,19 @@ public class RubberBandStretcher
     public native int getSamplesRequired();
 
     public native void setKeyFrameMap(long[] from, long[] to);
+    public void setKeyFrameMap(Map<Long, Long> m) {
+        Set<Long> keys = m.keySet();
+        int n = keys.size();
+        long[] from = new long[n];
+        long[] to = new long[n];
+        int i = 0;
+        for (Long k : keys) {
+            from[i] = k.longValue();
+            to[i] = m.get(k).longValue();
+            ++i;
+        }
+        setKeyFrameMap(from, to);
+    }
 
     public native void study(float[][] input, int offset, int n, boolean finalBlock);
     public void study(float[][] input, boolean finalBlock) {
diff --git a/com/breakfastquay/rubberband/test/RubberBandTest.java b/com/breakfastquay/rubberband/test/RubberBandTest.java
index d0e4637..578f5ec 100644
--- a/com/breakfastquay/rubberband/test/RubberBandTest.java
+++ b/com/breakfastquay/rubberband/test/RubberBandTest.java
@@ -3,6 +3,8 @@ package com.breakfastquay.rubberband.test;
 
 import com.breakfastquay.rubberband.RubberBandStretcher;
 
+import java.util.TreeMap;
+
 public class RubberBandTest
 {
 
@@ -15,7 +17,7 @@ public class RubberBandTest
             (rate,
              channels,
              RubberBandStretcher.OptionEngineFiner +
-             RubberBandStretcher.OptionProcessRealTime,
+             RubberBandStretcher.OptionProcessOffline,
              1.0,
              1.0);
 
@@ -38,11 +40,16 @@ public class RubberBandTest
                 ));
 
         int blocksize = 1024;
-        int blocks = 200;
+        int blocks = 400;
         double freq = 440.0;
         
         stretcher.setMaxProcessSize(blocksize);
 
+        TreeMap<Long, Long> keyFrameMap = new TreeMap<Long, Long>();
+        keyFrameMap.put((long)(3 * rate), (long)(4 * rate));
+        keyFrameMap.put((long)(5 * rate), (long)(5 * rate));
+        stretcher.setKeyFrameMap(keyFrameMap);
+
         float[][] buffer = new float[channels][blocksize];
 
         int i0 = 0;
@@ -53,6 +60,27 @@ public class RubberBandTest
                 for (int i = 0; i < blocksize; ++i) {
                     buffer[c][i] = (float)Math.sin
                         ((double)i0 * freq * Math.PI * 2.0 / (double)rate);
+                    if (i0 % rate == 0) {
+                        buffer[c][i] = 1.f;
+                    }
+                    ++i0;
+                }
+            }
+            
+            stretcher.study(buffer, block + 1 == blocks);
+        }
+
+        i0 = 0;
+
+        for (int block = 0; block < blocks; ++block) {
+
+            for (int c = 0; c < channels; ++c) {
+                for (int i = 0; i < blocksize; ++i) {
+                    buffer[c][i] = (float)Math.sin
+                        ((double)i0 * freq * Math.PI * 2.0 / (double)rate);
+                    if (i0 % rate == 0) {
+                        buffer[c][i] = 1.f;
+                    }
                     ++i0;
                 }
             }
diff --git a/src/jni/RubberBandStretcherJNI.cpp b/src/jni/RubberBandStretcherJNI.cpp
index df04a26..9cac5fb 100644
--- a/src/jni/RubberBandStretcherJNI.cpp
+++ b/src/jni/RubberBandStretcherJNI.cpp
@@ -183,6 +183,14 @@ JNIEXPORT jint JNICALL Java_com_breakfastquay_rubberband_RubberBandStretcher_get
 JNIEXPORT jint JNICALL Java_com_breakfastquay_rubberband_RubberBandStretcher_getSamplesRequired
   (JNIEnv *, jobject);
 
+/*
+ * Class:     com_breakfastquay_rubberband_RubberBandStretcher
+ * Method:    setKeyFrameMap
+ * Signature: ([J[J)V
+ */
+JNIEXPORT void JNICALL Java_com_breakfastquay_rubberband_RubberBandStretcher_setKeyFrameMap
+  (JNIEnv *, jobject, jlongArray, jlongArray);
+
 /*
  * Class:     com_breakfastquay_rubberband_RubberBandStretcher
  * Method:    study
@@ -365,6 +373,22 @@ Java_com_breakfastquay_rubberband_RubberBandStretcher_getSamplesRequired(JNIEnv
     return getStretcher(env, obj)->getSamplesRequired();
 }
 
+JNIEXPORT void JNICALL
+Java_com_breakfastquay_rubberband_RubberBandStretcher_setKeyFrameMap(JNIEnv *env, jobject obj, jlongArray from, jlongArray to)
+{
+    std::map<size_t, size_t> m;
+    int flen = env->GetArrayLength(from);
+    int tlen = env->GetArrayLength(to);
+    jlong *farr = env->GetLongArrayElements(from, 0);
+    jlong *tarr = env->GetLongArrayElements(to, 0);
+    for (int i = 0; i < flen && i < tlen; ++i) {
+        m[farr[i]] = tarr[i];
+    }
+    env->ReleaseLongArrayElements(from, farr, 0);
+    env->ReleaseLongArrayElements(to, tarr, 0);
+    getStretcher(env, obj)->setKeyFrameMap(m);
+}
+
 JNIEXPORT void JNICALL
 Java_com_breakfastquay_rubberband_RubberBandStretcher_study(JNIEnv *env, jobject obj, jobjectArray data, jint offset, jint n, jboolean final)
 {