diff --git a/java/src/org/broadinstitute/sting/playground/gatk/walkers/CovariateCounterWalker.java b/java/src/org/broadinstitute/sting/playground/gatk/walkers/CovariateCounterWalker.java
new file mode 100644
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+++ b/java/src/org/broadinstitute/sting/playground/gatk/walkers/CovariateCounterWalker.java
@@ -0,0 +1,139 @@
+package org.broadinstitute.sting.playground.gatk.walkers;
+
+import net.sf.samtools.SAMRecord;
+import org.broadinstitute.sting.gatk.LocusContext;
+import org.broadinstitute.sting.gatk.refdata.RefMetaDataTracker;
+import org.broadinstitute.sting.gatk.refdata.rodDbSNP;
+import org.broadinstitute.sting.gatk.walkers.LocusWalker;
+import org.broadinstitute.sting.gatk.walkers.WalkerName;
+import org.broadinstitute.sting.utils.cmdLine.Argument;
+
+import java.util.ArrayList;
+import java.util.List;
+
+@WalkerName("CountCovariates")
+public class CovariateCounterWalker extends LocusWalker<Integer, Integer> {
+    @Argument(fullName="MAX_READ_LENGTH", shortName="mrl", required=false,defaultValue="101")
+    public int MAX_READ_LENGTH;
+
+    @Argument(fullName="MAX_QUAL_SCORE", shortName="mqs", required=false,defaultValue="34")
+    public int MAX_QUAL_SCORE;
+    //public double MAX_REPORTED_QUAL_SCORE = 100.0;
+
+    int NDINUCS = 16;
+    RecalData[][][] data = new RecalData[MAX_READ_LENGTH+1][MAX_QUAL_SCORE+1][NDINUCS];
+    //RecalData[][][] data = new RecalData;
+    ArrayList<RecalData> flattenData = new ArrayList();
+
+    int nuc2num[];
+    char num2nuc[];
+
+    private class RecalData {
+        long N;
+        long B;
+        int pos;
+        int qual;
+        String dinuc;
+
+        public RecalData(int pos, int qual, String dinuc ) {
+            this.pos = pos;
+            this.qual = qual;
+            this.dinuc = dinuc;
+        }
+
+        public void inc(char curBase, char ref) {
+            N++;
+            B += nuc2num[curBase] == nuc2num[ref] ? 0 : 1;
+            //out.printf("%s %s\n", curBase, ref);
+        }
+
+        public String headerString() {
+            return ("pos, dinuc, qual, emp_qual, qual_diff, n, b");
+        }
+
+        public String toString() {
+            double empiricalQual = -10 * Math.log10((double)B / N);
+
+            if (empiricalQual > MAX_QUAL_SCORE) empiricalQual = MAX_QUAL_SCORE;
+            return String.format("%3d,%s,%3d,%5.1f,%5.1f,%6d,%6d", pos, dinuc, qual, empiricalQual, qual-empiricalQual, N, B);
+            //return String.format("%d\t%s\t%d\t%.1f\t%d\t%6d", pos, dinuc, qual, empiricalQual, N, B);
+        }
+    }
+
+    public void initialize() {
+        for ( int i = 0; i < MAX_READ_LENGTH+1; i++) {
+            for ( int j = 0; j < MAX_QUAL_SCORE+1; j++) {
+                for ( int k = 0; k < NDINUCS; k++) {
+                    String dinuc = dinucIndex2bases(k);
+                    RecalData datum = new RecalData(i, j, dinuc);
+                    data[i][j][k] = datum;
+                    flattenData.add(datum);
+                }
+            }
+        }
+    }
+
+    public Integer map(RefMetaDataTracker tracker, char ref, LocusContext context) {
+        rodDbSNP dbsnp = (rodDbSNP)tracker.lookup("dbSNP", null);
+        if ( dbsnp == null ) {
+            List<SAMRecord> reads = context.getReads();
+            List<Integer> offsets = context.getOffsets();
+            for (int i =0; i < reads.size(); i++ ) {
+                SAMRecord read = reads.get(i);
+                int offset = offsets.get(i);
+                if ( offset > 0 ) {
+                    char base = (char)read.getReadBases()[offset];
+                    char prevBase = (char)read.getReadBases()[offset-1];
+                    int qual = (int)read.getBaseQualities()[offset];
+                    //out.printf("%d %d %d\n", offset, qual, bases2dinucIndex(prevBase,base));
+                    RecalData datum = data[offset][qual][bases2dinucIndex(prevBase,base)];
+                    datum.inc(base,ref);
+                }
+            }
+        }
+        return 1;
+    }
+
+    public void onTraversalDone(Integer result) {
+        if (flattenData.size() > 0)
+            out.println(flattenData.get(0).headerString());
+        for ( RecalData datum : flattenData ) {
+            out.println(datum);
+        }
+    }
+
+    public Integer reduceInit() {
+        return 0;
+    }
+
+    public Integer reduce(Integer a, Integer b) {
+        return 0;
+    }
+
+    int bases2dinucIndex(char prevBase, char base) {
+        return nuc2num[prevBase] * 4 + nuc2num[base];
+    };
+
+    String dinucIndex2bases(int index) {
+        char data[] = {num2nuc[index / 4], num2nuc[index % 4]};
+        return new String( data );
+    }
+
+    public CovariateCounterWalker() {
+        nuc2num = new int[128];
+        nuc2num['A'] = 0;
+        nuc2num['C'] = 1;
+        nuc2num['G'] = 2;
+        nuc2num['T'] = 3;
+        nuc2num['a'] = 0;
+        nuc2num['c'] = 1;
+        nuc2num['g'] = 2;
+        nuc2num['t'] = 3;
+
+        num2nuc = new char[4];
+        num2nuc[0] = 'A';
+        num2nuc[1] = 'C';
+        num2nuc[2] = 'G';
+        num2nuc[3] = 'T';
+    }
+}
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