Interpolate gain changes smoothly, reusing the gain fading code from the EQ.

diff --git a/audio_mixer.cpp b/audio_mixer.cpp
index 506e78d50ede72820e08ba1acfecb6d6dbad8411..e4eb495953baaa49cd487f2b5e16960857d88efb 100644 (file)
--- a/audio_mixer.cpp
+++ b/audio_mixer.cpp
@@ -355,6 +355,7 @@ void AudioMixer::set_bus_settings(unsigned bus_index, const AudioMixer::BusSetti
                eq_level_db[bus_index][band_index] = settings.eq_level_db[band_index];
        }
        gain_staging_db[bus_index] = settings.gain_staging_db;
+       last_gain_staging_db[bus_index] = gain_staging_db[bus_index];
        level_compressor_enabled[bus_index] = settings.level_compressor_enabled;
        compressor_threshold_dbfs[bus_index] = settings.compressor_threshold_dbfs;
        compressor_enabled[bus_index] = settings.compressor_enabled;
@@ -438,6 +439,31 @@ vector<DeviceSpec> AudioMixer::get_active_devices() const
        return ret;
 }
 
+namespace {
+
+void apply_gain(float db, float last_db, vector<float> *samples)
+{
+       if (fabs(db - last_db) < 1e-3) {
+               // Constant over this frame.
+               const float gain = from_db(db);
+               for (size_t i = 0; i < samples->size(); ++i) {
+                       (*samples)[i] *= gain;
+               }
+       } else {
+               // We need to do a fade.
+               unsigned num_samples = samples->size() / 2;
+               float gain = from_db(last_db);
+               const float gain_inc = pow(from_db(db - last_db), 1.0 / num_samples);
+               for (size_t i = 0; i < num_samples; ++i) {
+                       (*samples)[i * 2 + 0] *= gain;
+                       (*samples)[i * 2 + 1] *= gain;
+                       gain *= gain_inc;
+               }
+       }
+}
+
+}  // namespace
+
 vector<float> AudioMixer::get_output(double pts, unsigned num_samples, ResamplingQueue::RateAdjustmentPolicy rate_adjustment_policy)
 {
        map<DeviceSpec, vector<float>> samples_card;
@@ -486,11 +512,11 @@ vector<float> AudioMixer::get_output(double pts, unsigned num_samples, Resamplin
                                gain_staging_db[bus_index] = to_db(level_compressor[bus_index]->get_attenuation() * makeup_gain);
                        } else {
                                // Just apply the gain we already had.
-                               float g = from_db(gain_staging_db[bus_index]);
-                               for (size_t i = 0; i < samples_bus.size(); ++i) {
-                                       samples_bus[i] *= g;
-                               }
+                               float db = gain_staging_db[bus_index];
+                               float last_db = last_gain_staging_db[bus_index];
+                               apply_gain(db, last_db, &samples_bus);
                        }
+                       last_gain_staging_db[bus_index] = gain_staging_db[bus_index];
 
 #if 0
                        printf("level=%f (%+5.2f dBFS) attenuation=%f (%+5.2f dB) end_result=%+5.2f dB\n",
@@ -642,22 +668,7 @@ void AudioMixer::apply_eq(unsigned bus_index, vector<float> *samples_bus)
        assert(samples_bus->size() % 2 == 0);
        const unsigned num_samples = samples_bus->size() / 2;
 
-       if (fabs(mid_db - last_mid_db) < 1e-3) {
-               // Constant over this frame.
-               const float gain = from_db(mid_db);
-               for (size_t i = 0; i < samples_bus->size(); ++i) {
-                       (*samples_bus)[i] *= gain;
-               }
-       } else {
-               // We need to do a fade.
-               float gain = from_db(last_mid_db);
-               const float gain_inc = pow(from_db(mid_db - last_mid_db), 1.0 / num_samples);
-               for (size_t i = 0; i < num_samples; ++i) {
-                       (*samples_bus)[i * 2 + 0] *= gain;
-                       (*samples_bus)[i * 2 + 1] *= gain;
-                       gain *= gain_inc;
-               }
-       }
+       apply_gain(mid_db, last_mid_db, samples_bus);
 
        apply_filter_fade(&eq[bus_index][EQ_BAND_BASS], samples_bus->data(), num_samples, bass_freq_hz, bass_db - mid_db, last_bass_db - last_mid_db);
        apply_filter_fade(&eq[bus_index][EQ_BAND_TREBLE], samples_bus->data(), num_samples, treble_freq_hz, treble_db - mid_db, last_treble_db - last_mid_db);

diff --git a/audio_mixer.h b/audio_mixer.h
index 789cd1dcf0bb5b56b0042089632c90ce94cc4ac5..71f36629341f54a6151d33469271efd6361ccbce 100644 (file)
--- a/audio_mixer.h
+++ b/audio_mixer.h
@@ -336,6 +336,7 @@ private:
        mutable std::mutex compressor_mutex;
        std::unique_ptr<StereoCompressor> level_compressor[MAX_BUSES];  // Under compressor_mutex. Used to set/override gain_staging_db if <level_compressor_enabled>.
        float gain_staging_db[MAX_BUSES];  // Under compressor_mutex.
+       float last_gain_staging_db[MAX_BUSES];  // Under compressor_mutex.
        bool level_compressor_enabled[MAX_BUSES];  // Under compressor_mutex.
 
        static constexpr float ref_level_dbfs = -14.0f;  // Chosen so that we end up around 0 LU in practice.