ggwave : add "soundMarkerThreshold" parameter

Can be used to control the threshold used for distinguishing odd from even frequencies in the sound markers.
ggerganov · Feb 20, 2021 · f4fb02d · f4fb02d
1 parent 6011c0c
commit f4fb02d
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Showing 5 changed files with 14 additions and 5 deletions.
diff --git a/examples/ggwave-common-sdl2.cpp b/examples/ggwave-common-sdl2.cpp
@@ -220,6 +220,7 @@ bool GGWave_init(
             g_obtainedSpecInp.freq,
             g_obtainedSpecOut.freq,
             GGWave::kDefaultSamplesPerFrame,
+            GGWave::kDefaultSoundMarkerThreshold,
             sampleFormatInp,
             sampleFormatOut});
     }

diff --git a/examples/ggwave-to-file/main.cpp b/examples/ggwave-to-file/main.cpp
@@ -69,7 +69,7 @@ int main(int argc, char** argv) {
 
     fprintf(stderr, "Generating waveform for message '%s' ...\n", message.c_str());
 
-    GGWave ggWave({ -1, GGWave::kBaseSampleRate, sampleRateOut, 1024, GGWAVE_SAMPLE_FORMAT_F32, GGWAVE_SAMPLE_FORMAT_I16 });
+    GGWave ggWave({ -1, GGWave::kBaseSampleRate, sampleRateOut, 1024, GGWave::kDefaultSamplesPerFrame, GGWAVE_SAMPLE_FORMAT_F32, GGWAVE_SAMPLE_FORMAT_I16 });
     ggWave.init(message.size(), message.data(), ggWave.getTxProtocol(protocolId), volume);
 
     std::vector<char> bufferPCM;

diff --git a/include/ggwave/ggwave.h b/include/ggwave/ggwave.h
@@ -69,6 +69,7 @@ extern "C" {
         int sampleRateInp;                      // capture sample rate
         int sampleRateOut;                      // playback sample rate
         int samplesPerFrame;                    // number of samples per audio frame
+        float soundMarkerThreshold;             // sound marker detection threshold
         ggwave_SampleFormat sampleFormatInp;    // format of the captured audio samples
         ggwave_SampleFormat sampleFormatOut;    // format of the playback audio samples
     } ggwave_Parameters;
@@ -225,6 +226,7 @@ class GGWave {
     static constexpr auto kBaseSampleRate = 48000;
     static constexpr auto kDefaultSamplesPerFrame = 1024;
     static constexpr auto kDefaultVolume = 10;
+    static constexpr auto kDefaultSoundMarkerThreshold = 3.0f;
     static constexpr auto kMaxSamplesPerFrame = 2048;
     static constexpr auto kMaxDataBits = 256;
     static constexpr auto kMaxDataSize = 256;
@@ -378,6 +380,8 @@ class GGWave {
     const int m_nMarkerFrames;
     const int m_encodedDataOffset;
 
+    const float m_soundMarkerThreshold;
+
     // common
 
     bool m_isFixedPayloadLength;

diff --git a/src/ggwave.cpp b/src/ggwave.cpp
@@ -33,6 +33,7 @@ ggwave_Instance ggwave_init(const ggwave_Parameters parameters) {
             parameters.sampleRateInp,
             parameters.sampleRateOut,
             parameters.samplesPerFrame,
+            parameters.soundMarkerThreshold,
             parameters.sampleFormatInp,
             parameters.sampleFormatOut});
 
@@ -275,6 +276,7 @@ const GGWave::Parameters & GGWave::getDefaultParameters() {
         kBaseSampleRate,
         kBaseSampleRate,
         kDefaultSamplesPerFrame,
+        kDefaultSoundMarkerThreshold,
         GGWAVE_SAMPLE_FORMAT_F32,
         GGWAVE_SAMPLE_FORMAT_F32,
     };
@@ -298,6 +300,7 @@ GGWave::GGWave(const Parameters & parameters) :
     m_nBitsInMarker(16),
     m_nMarkerFrames(parameters.payloadLength > 0 ? 0 : 16),
     m_encodedDataOffset(parameters.payloadLength > 0 ? 0 : 3),
+    m_soundMarkerThreshold(parameters.soundMarkerThreshold),
     // common
     m_isFixedPayloadLength(parameters.payloadLength > 0),
     m_payloadLength(parameters.payloadLength),
@@ -1047,9 +1050,9 @@ void GGWave::decode_variable() {
                 int bin = std::round(freq*m_ihzPerSample);
 
                 if (i%2 == 0) {
-                    if (m_sampleSpectrum[bin] <= 3.0f*m_sampleSpectrum[bin + m_freqDelta_bin]) --nDetectedMarkerBits;
+                    if (m_sampleSpectrum[bin] <= m_soundMarkerThreshold*m_sampleSpectrum[bin + m_freqDelta_bin]) --nDetectedMarkerBits;
                 } else {
-                    if (m_sampleSpectrum[bin] >= 3.0f*m_sampleSpectrum[bin + m_freqDelta_bin]) --nDetectedMarkerBits;
+                    if (m_sampleSpectrum[bin] >= m_soundMarkerThreshold*m_sampleSpectrum[bin + m_freqDelta_bin]) --nDetectedMarkerBits;
                 }
             }
 
@@ -1096,9 +1099,9 @@ void GGWave::decode_variable() {
                 int bin = std::round(freq*m_ihzPerSample);
 
                 if (i%2 == 0) {
-                    if (m_sampleSpectrum[bin] >= 3.0f*m_sampleSpectrum[bin + m_freqDelta_bin]) nDetectedMarkerBits--;
+                    if (m_sampleSpectrum[bin] >= m_soundMarkerThreshold*m_sampleSpectrum[bin + m_freqDelta_bin]) nDetectedMarkerBits--;
                 } else {
-                    if (m_sampleSpectrum[bin] <= 3.0f*m_sampleSpectrum[bin + m_freqDelta_bin]) nDetectedMarkerBits--;
+                    if (m_sampleSpectrum[bin] <= m_soundMarkerThreshold*m_sampleSpectrum[bin + m_freqDelta_bin]) nDetectedMarkerBits--;
                 }
             }
 

diff --git a/tests/test-ggwave.cpp b/tests/test-ggwave.cpp
@@ -192,6 +192,7 @@ int main(int argc, char ** argv) {
     // playback / capture at different sample rates
     for (int srInp = GGWave::kBaseSampleRate/3; srInp <= 2*GGWave::kBaseSampleRate; srInp += 1100) {
         auto parameters = GGWave::getDefaultParameters();
+        parameters.soundMarkerThreshold = 1.1f;
 
         std::string payload = "hello123";