Index: mp3.cpp
===================================================================
--- mp3.cpp	(revision 52194)
+++ mp3.cpp	(working copy)
@@ -83,9 +83,13 @@
 	int readBuffer(int16 *buffer, const int numSamples);
 
 	bool endOfData() const		{ return _state == MP3_STATE_EOS; }
-	bool isStereo() const		{ return MAD_NCHANNELS(&_frame.header) == 2; }
 	int getRate() const			{ return _frame.header.samplerate; }
 
+	// We return true for stereo always because MPEG audio files can
+	// change the number of channels at any time. In mono samples,
+	// we just duplicate the sample for the second channel.
+	bool isStereo() const		{ return true; }
+
 	bool seek(const Timestamp &where);
 	Timestamp getLength() const { return _length; }
 protected:
@@ -327,10 +331,17 @@
 		while (samples < len) {
 			*buffer++ = (int16)scale_sample(_synth.pcm.samples[0][_posInFrame]);
 			samples++;
+
 			if (MAD_NCHANNELS(&_frame.header) == 2) {
 				*buffer++ = (int16)scale_sample(_synth.pcm.samples[1][_posInFrame]);
 				samples++;
+			} else {
+				// For mono, just duplicate the sample for both channels
+				// See above for more details
+				*buffer = *(buffer - 1);
+				buffer++;
 			}
+
 			_posInFrame++;
 		}
 		if (_posInFrame >= _synth.pcm.length) {