* Fix failure to remember that we have constructed an interpolator

window already (#25).  Also avoid using alloca for substantial buffers
* Lose FFT::getFloatTimeBuffer and getDoubleTimeBuffer -- it's too
unclear when it's safe to use them and it's safer to control sizes externally.
In RB with smoothing on, these buffers were incorrectly being used for window-si
zed calculations (larger than FFT-sized).
* Fix some incorrect buffer resize sizes
* Build fixes for OS/X

README.txt

@@ -4,10 +4,29 @@ Rubber Band
 
 An audio time-stretching and pitch-shifting library and utility program.
 
-Copyright 2007-2010 Chris Cannam, chris.cannam@breakfastquay.com.
+Copyright 2007-2011 Chris Cannam, chris.cannam@breakfastquay.com.
 
 Distributed under the GNU General Public License.
 
+
+Contents
+========
+
+1. About Rubber Band
+    - Attractive features
+    - Limitations
+
+2. Compiling Rubber Band
+
+3. Using the Rubber Band utility
+
+4. Using the Rubber Band library
+
+
+
+About Rubber Band
+-----------------
+
 Rubber Band is a library and utility program that permits you to
 change the tempo and pitch of an audio recording independently of one
 another.
@@ -90,11 +109,15 @@ Limitations
 Compiling Rubber Band
 ---------------------
 
-Rubber Band is supplied with build scripts that have been tested on
+Rubber Band Library is supplied with a configure script for Linux and
-Linux platforms.  It is also possible to build Rubber Band on other
+other systems with pkg-config, and a separate Makefile for basic OS/X
-platforms, including both POSIX platforms such as OS/X and non-POSIX
+builds without pkg-config.  It's also possible to build the Rubber
-platforms such as Win32.  There are some example Makefiles in the misc
+Band Library GPL edition for Windows using MinGW, though you'll have
-directory.
+to hack your own Makefile for that.
+
+
+Using configure
+~~~~~~~~~~~~~~~
 
 To build Rubber Band you will also need libsndfile, libsamplerate,
 FFTW3, the Vamp plugin SDK, the LADSPA plugin header, the pthread
@@ -113,6 +136,18 @@ to compile, and optionally
 to install.
 
 
+Simple build for OS/X
+~~~~~~~~~~~~~~~~~~~~~
+
+To build just the library (but not the command-line utility, Vamp
+plugin or LADSPA plugin) for OS/X, run
+
+  $ make -f build/Makefile.osx
+
+You will need libsamplerate and libfftw3 installed, but no other
+non-system dependencies.
+
+
 Using the Rubber Band utility
 -----------------------------
 

build/Makefile.osx

@@ -3,8 +3,12 @@
 # Does not build the Vamp plugin, LADSPA plugin, or command-line utility.
 
 CXX		:= g++
-CXXFLAGS	:= -DHAVE_FFTW3 -DFFTW_DOUBLE_ONLY -DNO_THREAD_CHECKS -DNO_TIMING -DNDEBUG -mmacosx-version-min=10.4 -isysroot /Developer/SDKs/MacOSX10.4u.sdk -O3 -arch i386 -arch ppc -msse -msse2 -ffast-math -ftree-vectorize -I../include -I/usr/local/include -Irubberband -I. -Isrc
+CXXFLAGS	:= -DHAVE_FFTW3 -DFFTW_DOUBLE_ONLY -DNO_THREAD_CHECKS -DNO_TIMING -DNDEBUG -O3 -arch i386 -arch x86_64 -msse -msse2 -ffast-math -ftree-vectorize -I../include -I/usr/local/include -Irubberband -I. -Isrc
-LDFLAGS		:= -mmacosx-version-min=10.4 -isysroot /Developer/SDKs/MacOSX10.4u.sdk -arch i386 -arch ppc -L../lib -L/usr/local/lib
+LDFLAGS		:= -arch i386 -arch x86_64 -L../lib -L/usr/local/lib
+
+# CXX		:= g++-4.0
+# CXXFLAGS	:= -DHAVE_FFTW3 -DFFTW_DOUBLE_ONLY -DNO_THREAD_CHECKS -DNO_TIMING -DNDEBUG -mmacosx-version-min=10.4 -isysroot /Developer/SDKs/MacOSX10.4u.sdk -O3 -arch i386 -msse -msse2 -ffast-math -ftree-vectorize -I../include -I/usr/local/include -Irubberband -I. -Isrc
+# LDFLAGS		:= -mmacosx-version-min=10.4 -isysroot /Developer/SDKs/MacOSX10.4u.sdk -arch i386 -L../lib -L/usr/local/lib
 
 LIBRARY_LIBS		:= -lsamplerate -lfftw3 -lpthread -lm
 

main/main.cpp

@@ -26,13 +26,9 @@
 
 #include "system/sysutils.h"
 
-#ifdef __MSVC__
-#include "getopt/getopt.h"
-#else
 #include <getopt.h>
 #include <unistd.h>
 #include <sys/time.h>
-#endif
 
 #include "base/Profiler.h"
 
@@ -43,9 +39,6 @@ using namespace RubberBand;
 using RubberBand::gettimeofday;
 #endif
 
-#ifdef __MSVC__
-using RubberBand::usleep;
-#endif
 
 double tempo_convert(const char *str)
 {

src/StretcherChannelData.cpp

@@ -70,9 +70,10 @@ RubberBandStretcher::Impl::ChannelData::construct(const std::set<size_t> &sizes,
     unwrappedPhase = allocate_and_zero<process_t>(realSize);
     envelope = allocate_and_zero<process_t>(realSize);
 
-    freqPeak = new size_t[realSize];
+    freqPeak = allocate_and_zero<size_t>(realSize);
 
     fltbuf = allocate_and_zero<float>(maxSize);
+    dblbuf = allocate_and_zero<process_t>(maxSize);
 
     accumulator = allocate_and_zero<float>(maxSize);
     windowAccumulator = allocate_and_zero<float>(maxSize);
@@ -90,31 +91,12 @@ RubberBandStretcher::Impl::ChannelData::construct(const std::set<size_t> &sizes,
     }
     fft = ffts[initialFftSize];
 
-    if (sizeof(process_t) == sizeof(double)) {
-        dblbuf = (process_t *)fft->getDoubleTimeBuffer();
-    } else {
-        dblbuf = (process_t *)fft->getFloatTimeBuffer();
-    }
-
     resampler = 0;
     resamplebuf = 0;
     resamplebufSize = 0;
 
     reset();
 
-    for (size_t i = 0; i < realSize; ++i) {
-        freqPeak[i] = 0;
-    }
-
-    for (size_t i = 0; i < initialFftSize; ++i) {
-        dblbuf[i] = 0.0;
-    }
-
-    for (size_t i = 0; i < maxSize; ++i) {
-        accumulator[i] = 0.f;
-        windowAccumulator[i] = 0.f;
-    }
-
     // Avoid dividing opening sample (which will be discarded anyway) by zero
     windowAccumulator[0] = 1.f;
 }
@@ -127,6 +109,7 @@ RubberBandStretcher::Impl::ChannelData::setSizes(size_t windowSize,
     size_t maxSize = std::max(windowSize, fftSize);
     size_t realSize = maxSize / 2 + 1;
     size_t oldMax = inbuf->getSize();
+    size_t oldReal = oldMax / 2 + 1;
 
     if (oldMax >= maxSize) {
 
@@ -149,12 +132,7 @@ RubberBandStretcher::Impl::ChannelData::setSizes(size_t windowSize,
         
         fft = ffts[fftSize];
 
-        if (sizeof(process_t) == sizeof(double)) {
+        v_zero(fltbuf, maxSize);
-            dblbuf = (process_t *)fft->getDoubleTimeBuffer();
-        } else {
-            dblbuf = (process_t *)fft->getFloatTimeBuffer();
-        }
-
         v_zero(dblbuf, maxSize);
 
         v_zero(mag, realSize);
@@ -180,34 +158,25 @@ RubberBandStretcher::Impl::ChannelData::setSizes(size_t windowSize,
 
     // We don't want to preserve data in these arrays
 
-    mag = reallocate_and_zero<process_t>(mag, oldMax, realSize);
+    mag = reallocate_and_zero(mag, oldReal, realSize);
-    phase = reallocate_and_zero<process_t>(phase, oldMax, realSize);
+    phase = reallocate_and_zero(phase, oldReal, realSize);
-    prevPhase = reallocate_and_zero<process_t>(prevPhase, oldMax, realSize);
+    prevPhase = reallocate_and_zero(prevPhase, oldReal, realSize);
-    prevError = reallocate_and_zero<process_t>(prevError, oldMax, realSize);
+    prevError = reallocate_and_zero(prevError, oldReal, realSize);
-    unwrappedPhase = reallocate_and_zero<process_t>(unwrappedPhase, oldMax, realSize);
+    unwrappedPhase = reallocate_and_zero(unwrappedPhase, oldReal, realSize);
-    envelope = reallocate_and_zero<process_t>(envelope, oldMax, realSize);
+    envelope = reallocate_and_zero(envelope, oldReal, realSize);
+    freqPeak = reallocate_and_zero(freqPeak, oldReal, realSize);
+    fltbuf = reallocate_and_zero(fltbuf, oldMax, maxSize);
+    dblbuf = reallocate_and_zero(dblbuf, oldMax, maxSize);
 
-    delete[] freqPeak;
+    interpolator = reallocate_and_zero<float>(interpolator, oldMax, maxSize);
-    freqPeak = new size_t[realSize];
-
-    deallocate(fltbuf);
-    fltbuf = allocate_and_zero<float>(maxSize);
 
     // But we do want to preserve data in these
 
-    float *newAcc = allocate_and_zero<float>(maxSize);
+    accumulator = reallocate_and_zero_extension
+        (accumulator, oldMax, maxSize);
 
-    v_copy(newAcc, accumulator, oldMax);
+    windowAccumulator = reallocate_and_zero_extension
-
+        (windowAccumulator, oldMax, maxSize);
-    deallocate(accumulator);
-    accumulator = newAcc;
-
-    newAcc = allocate_and_zero<float>(maxSize);
-
-    v_copy(newAcc, windowAccumulator, oldMax);
-
-    deallocate(windowAccumulator);
-    windowAccumulator = newAcc;
 
     interpolatorScale = 0;
     
@@ -223,14 +192,6 @@ RubberBandStretcher::Impl::ChannelData::setSizes(size_t windowSize,
     }
     
     fft = ffts[fftSize];
-
-    if (sizeof(process_t) == sizeof(double)) {
-        dblbuf = (process_t *)fft->getDoubleTimeBuffer();
-    } else {
-        dblbuf = (process_t *)fft->getFloatTimeBuffer();
-    }
-
-    v_zero(dblbuf, fftSize);
 }
 
 void
@@ -273,7 +234,7 @@ RubberBandStretcher::Impl::ChannelData::~ChannelData()
     deallocate(prevError);
     deallocate(unwrappedPhase);
     deallocate(envelope);
-    delete[] freqPeak;
+    deallocate(freqPeak);
     deallocate(accumulator);
     deallocate(windowAccumulator);
     deallocate(fltbuf);

src/StretcherImpl.cpp

@@ -783,8 +783,10 @@ RubberBandStretcher::Impl::reconfigure()
                 new Resampler(Resampler::FastestTolerable, 1, m_sWindowSize,
                               m_debugLevel);
 
-            m_channelData[c]->setResampleBufSize
+            size_t rbs = 
-                (lrintf(ceil((m_increment * m_timeRatio * 2) / m_pitchScale)));
+                lrintf(ceil((m_increment * m_timeRatio * 2) / m_pitchScale));
+            if (rbs < m_increment * 16) rbs = m_increment * 16;
+            m_channelData[c]->setResampleBufSize(rbs);
         }
     }
 

src/StretcherProcess.cpp

@@ -910,22 +910,27 @@ RubberBandStretcher::Impl::synthesiseChunk(size_t channel,
     }
 
     if (wsz > fsz) {
-        float *tmp = (float *)alloca(wsz * sizeof(float));
         int p = shiftIncrement * 2;
         if (cd.interpolatorScale != p) {
             SincWindow<float>::write(cd.interpolator, wsz, p);
+            cd.interpolatorScale = p;
         }
         v_multiply(fltbuf, cd.interpolator, wsz);
-        v_copy(tmp, cd.interpolator, wsz);
-        m_swindow->cut(tmp);
-        v_add(windowAccumulator, tmp, wsz);
-    } else {
-        m_swindow->add(windowAccumulator, m_awindow->getArea() * 1.5f);
     }
 
     m_swindow->cut(fltbuf);
     v_add(accumulator, fltbuf, wsz);
     cd.accumulatorFill = wsz;
+
+    if (wsz > fsz) {
+        // reuse fltbuf to calculate interpolating window shape for
+        // window accumulator
+        v_copy(fltbuf, cd.interpolator, wsz);
+        m_swindow->cut(fltbuf);
+        v_add(windowAccumulator, fltbuf, wsz);
+    } else {
+        m_swindow->add(windowAccumulator, m_awindow->getArea() * 1.5f);
+    }
 }
 
 void

src/base/Scavenger.h

@@ -43,6 +43,9 @@ namespace RubberBand {
  * -- it's just a quick hack for use with things like plugins.
  */
 
+//!!! should review this, it's not really thread safe owing to lack of
+//!!! atomic updates
+
 template <typename T>
 class Scavenger
 {

src/dsp/CompoundAudioCurve.cpp

@@ -28,6 +28,7 @@ CompoundAudioCurve::CompoundAudioCurve(Parameters parameters) :
     m_hf(parameters),
     m_hfFilter(new MovingMedian<double>(19, 85)),
     m_hfDerivFilter(new MovingMedian<double>(19, 90)),
+    m_type(CompoundDetector),
     m_lastHf(0.0),
     m_lastResult(0.0),
     m_risingCount(0)

src/dsp/CompoundAudioCurve.h

@@ -35,7 +35,7 @@ public:
         CompoundDetector,
         SoftDetector
     };
-    virtual void setType(Type);
+    virtual void setType(Type); // default is CompoundDetector
     
     virtual void setFftSize(int newSize);
 

src/dsp/FFT.cpp

@@ -17,8 +17,9 @@
 #include "base/Profiler.h"
 #include "system/Allocators.h"
 #include "system/VectorOps.h"
+#include "system/VectorOpsComplex.h"
 
-//#define FFT_MEASUREMENT 1
+#define FFT_MEASUREMENT 1
 
 
 #ifdef HAVE_FFTW3
@@ -77,9 +78,6 @@ public:
     virtual void inverseInterleaved(const float *R__ complexIn, float *R__ realOut) = 0;
     virtual void inversePolar(const float *R__ magIn, const float *R__ phaseIn, float *R__ realOut) = 0;
     virtual void inverseCepstral(const float *R__ magIn, float *R__ cepOut) = 0;
-
-    virtual float *getFloatTimeBuffer() = 0;
-    virtual double *getDoubleTimeBuffer() = 0;
 };    
 
 namespace FFTs {
@@ -152,15 +150,8 @@ namespace FFTs {
 class D_FFTW : public FFTImpl
 {
 public:
-    D_FFTW(int size) : m_fplanf(0)
+    D_FFTW(int size) :
-#ifdef FFTW_DOUBLE_ONLY
+        m_fplanf(0), m_dplanf(0), m_size(size)
-                              , m_frb(0)
-#endif
-                              , m_dplanf(0)
-#ifdef FFTW_FLOAT_ONLY
-                              , m_drb(0)
-#endif
-                              , m_size(size)
     {
     }
 
@@ -176,9 +167,6 @@ public:
             fftwf_destroy_plan(m_fplani);
             fftwf_free(m_fbuf);
             fftwf_free(m_fpacked);
-#ifdef FFTW_DOUBLE_ONLY
-            if (m_frb) fftw_free(m_frb);
-#endif
             m_commonMutex.unlock();
         }
         if (m_dplanf) {
@@ -192,9 +180,6 @@ public:
             fftw_destroy_plan(m_dplani);
             fftw_free(m_dbuf);
             fftw_free(m_dpacked);
-#ifdef FFTW_FLOAT_ONLY
-            if (m_drb) fftwf_free(m_drb);
-#endif
             m_commonMutex.unlock();
         }
     }
@@ -390,14 +375,8 @@ public:
                 dbuf[i] = realIn[i];
             }
         fftw_execute(m_dplanf);
-        const int hs = m_size/2;
+        v_cartesian_interleaved_to_polar(magOut, phaseOut,
-        for (int i = 0; i <= hs; ++i) {
+                                         (double *)m_dpacked, m_size/2+1);
-            magOut[i] = sqrt(m_dpacked[i][0] * m_dpacked[i][0] +
-                             m_dpacked[i][1] * m_dpacked[i][1]);
-        }
-        for (int i = 0; i <= hs; ++i) {
-            phaseOut[i] = atan2(m_dpacked[i][1], m_dpacked[i][0]);
-        }
     }
 
     void forwardMagnitude(const double *R__ realIn, double *R__ magOut) {
@@ -457,14 +436,8 @@ public:
                 fbuf[i] = realIn[i];
             }
         fftwf_execute(m_fplanf);
-        const int hs = m_size/2;
+        v_cartesian_interleaved_to_polar(magOut, phaseOut,
-        for (int i = 0; i <= hs; ++i) {
+                                         (float *)m_fpacked, m_size/2+1);
-            magOut[i] = sqrtf(m_fpacked[i][0] * m_fpacked[i][0] +
-                              m_fpacked[i][1] * m_fpacked[i][1]);
-        }
-        for (int i = 0; i <= hs; ++i) {
-            phaseOut[i] = atan2f(m_fpacked[i][1], m_fpacked[i][0]) ;
-        }
     }
 
     void forwardMagnitude(const float *R__ realIn, float *R__ magOut) {
@@ -625,31 +598,10 @@ public:
             }
     }
 
-    float *getFloatTimeBuffer() {
-        initFloat();
-#ifdef FFTW_DOUBLE_ONLY
-        if (!m_frb) m_frb = (float *)fftw_malloc(m_size * sizeof(float));
-        return m_frb;
-#else
-        return m_fbuf;
-#endif
-    }
-
-    double *getDoubleTimeBuffer() {
-        initDouble();
-#ifdef FFTW_FLOAT_ONLY
-        if (!m_drb) m_drb = (double *)fftwf_malloc(m_size * sizeof(double));
-        return m_drb;
-#else
-        return m_dbuf;
-#endif
-    }
-
 private:
     fftwf_plan m_fplanf;
     fftwf_plan m_fplani;
 #ifdef FFTW_DOUBLE_ONLY
-    float *m_frb;
     double *m_fbuf;
 #else
     float *m_fbuf;
@@ -659,11 +611,10 @@ private:
     fftw_plan m_dplani;
 #ifdef FFTW_FLOAT_ONLY
     float *m_dbuf;
-    double *m_drb;
 #else
     double *m_dbuf;
 #endif
-    fftw_complex * m_dpacked;
+    fftw_complex *m_dpacked;
     const int m_size;
     static int m_extantf;
     static int m_extantd;
@@ -688,8 +639,6 @@ class D_KISSFFT : public FFTImpl
 public:
     D_KISSFFT(int size) :
         m_size(size),
-        m_frb(0),
-        m_drb(0),
         m_fplanf(0),  
         m_fplani(0)
     {
@@ -714,9 +663,6 @@ public:
 
         delete[] m_fbuf;
         delete[] m_fpacked;
-
-        if (m_frb) delete[] m_frb;
-        if (m_drb) delete[] m_drb;
     }
 
     void initFloat() { }
@@ -957,20 +903,8 @@ public:
         kiss_fftri(m_fplani, m_fpacked, cepOut);
     }
 
-    float *getFloatTimeBuffer() {
-        if (!m_frb) m_frb = new float[m_size];
-        return m_frb;
-    }
-
-    double *getDoubleTimeBuffer() {
-        if (!m_drb) m_drb = new double[m_size];
-        return m_drb;
-    }
-
 private:
     const int m_size;
-    float* m_frb;
-    double* m_drb;
     kiss_fftr_cfg m_fplanf;
     kiss_fftr_cfg m_fplani;
     kiss_fft_scalar *m_fbuf;
@@ -984,7 +918,7 @@ private:
 class D_Cross : public FFTImpl
 {
 public:
-    D_Cross(int size) : m_size(size), m_table(0), m_frb(0), m_drb(0) {
+    D_Cross(int size) : m_size(size), m_table(0) {
         
         m_a = new double[size];
         m_b = new double[size];
@@ -1022,8 +956,6 @@ public:
         delete[] m_b;
         delete[] m_c;
         delete[] m_d;
-        delete[] m_frb;
-        delete[] m_drb;
     }
 
     void initFloat() { }
@@ -1221,21 +1153,9 @@ public:
         for (int i = 0; i < m_size; ++i) cepOut[i] = m_c[i];
     }
 
-    float *getFloatTimeBuffer() {
-        if (!m_frb) m_frb = new float[m_size];
-        return m_frb;
-    }
-
-    double *getDoubleTimeBuffer() {
-        if (!m_drb) m_drb = new double[m_size];
-        return m_drb;
-    }
-
 private:
     const int m_size;
     int *m_table;
-    float *m_frb;
-    double *m_drb;
     double *m_a;
     double *m_b;
     double *m_c;
@@ -1561,18 +1481,6 @@ FFT::initDouble()
     d->initDouble();
 }
 
-float *
-FFT::getFloatTimeBuffer()
-{
-    return d->getFloatTimeBuffer();
-}
-
-double *
-FFT::getDoubleTimeBuffer()
-{
-    return d->getDoubleTimeBuffer();
-}
-
 
 void
 FFT::tune()

src/dsp/FFT.h

@@ -73,9 +73,6 @@ public:
     void initFloat();
     void initDouble();
 
-    float *getFloatTimeBuffer();
-    double *getDoubleTimeBuffer();
-
     static void tune();
 
 protected:

src/dsp/PercussiveAudioCurve.cpp

@@ -43,7 +43,7 @@ PercussiveAudioCurve::reset()
 void
 PercussiveAudioCurve::setFftSize(int newSize)
 {
-    m_prevMag = reallocate(m_prevMag, m_fftSize, newSize);
+    m_prevMag = reallocate(m_prevMag, m_fftSize/2 + 1, newSize/2 + 1);
     AudioCurveCalculator::setFftSize(newSize);
     reset();
 }

src/dsp/Resampler.cpp

@@ -506,6 +506,14 @@ Resampler::Resampler(Resampler::Quality quality, int channels,
 #endif
         break;
     }
+
+    if (!d) {
+        std::cerr << "Resampler::Resampler(" << quality << ", " << channels
+                  << ", " << maxBufferSize
+                  << "): Internal error: No implementation selected"
+                  << std::endl;
+        abort();
+    }
 }
 
 Resampler::~Resampler()

src/system/Allocators.h

@@ -70,6 +70,7 @@ void deallocate(T *ptr)
 }
 
 
+/// Reallocate preserving contents but leaving additional memory uninitialised	
 template <typename T>
 T *reallocate(T *ptr, size_t oldcount, size_t count)
 {
@@ -87,6 +88,7 @@ T *reallocate(T *ptr, size_t oldcount, size_t count)
     return newptr;
 }
 
+/// Reallocate, zeroing all contents
 template <typename T>
 T *reallocate_and_zero(T *ptr, size_t oldcount, size_t count)
 {
@@ -95,6 +97,15 @@ T *reallocate_and_zero(T *ptr, size_t oldcount, size_t count)
     return ptr;
 }
 	
+/// Reallocate preserving contents and zeroing any additional memory	
+template <typename T>
+T *reallocate_and_zero_extension(T *ptr, size_t oldcount, size_t count)
+{
+    ptr = reallocate(ptr, oldcount, count);
+    if (count > oldcount) v_zero(ptr + oldcount, count - oldcount);
+    return ptr;
+}
+
 template <typename T>
 T **allocate_channels(size_t channels, size_t count)
 {

src/system/Thread.h

@@ -99,26 +99,26 @@ private:
     Mutex *m_mutex;
 };
 
+/**
+  The Condition class bundles a condition variable and mutex.
+
+  To wait on a condition, call lock(), test the termination condition
+  if desired, then wait().  The condition will be unlocked during the
+  wait and re-locked when wait() returns (which will happen when the
+  condition is signalled or the timer times out).
+
+  To signal a condition, call signal().  If the condition is signalled
+  between lock() and wait(), the signal may be missed by the waiting
+  thread.  To avoid this, the signalling thread should also lock the
+  condition before calling signal() and unlock it afterwards.
+*/
+
 class Condition
 {
 public:
     Condition(std::string name);
     ~Condition();
     
-    // The Condition class bundles a condition variable and mutex.
-
-    // To wait on a condition, call lock(), test the termination
-    // condition if desired, then wait().  The condition will be
-    // unlocked during the wait and re-locked when wait() returns
-    // (which will happen when the condition is signalled or the timer
-    // times out).
-
-    // To signal a condition, call signal().  If the condition is
-    // signalled between lock() and wait(), the signal may be missed
-    // by the waiting thread.  To avoid this, the signalling thread
-    // should also lock the condition before calling signal() and
-    // unlock it afterwards.
-
     void lock();
     void unlock();
     void wait(int us = 0);