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Fix Spectrum Analyzer effect returning jittered values #114355

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Fix Spectrum Analyzer effect returning jittered values #114355

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191d2c9
Remove unused tap_back_pos from docs
Akosmo Dec 26, 2025
2484b89
Remove unused tap_back_pos from header file
Akosmo Dec 26, 2025
1981eaa
Remove FFT time difference lines from Spectrum Analyzer effect
Akosmo Dec 26, 2025
7573227
Add extension API validation file
Akosmo Dec 27, 2025
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2 changes: 0 additions & 2 deletions doc/classes/AudioEffectSpectrumAnalyzer.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -18,8 +18,6 @@
<member name="fft_size" type="int" setter="set_fft_size" getter="get_fft_size" enum="AudioEffectSpectrumAnalyzer.FFTSize" default="2">
The size of the [url=https://en.wikipedia.org/wiki/Fast_Fourier_transform]Fast Fourier transform[/url] buffer. Higher values smooth out the spectrum analysis over time, but have greater latency. The effects of this higher latency are especially noticeable with sudden amplitude changes.
</member>
<member name="tap_back_pos" type="float" setter="set_tap_back_pos" getter="get_tap_back_pos" default="0.01">
</member>
</members>
<constants>
<constant name="FFT_SIZE_256" value="0" enum="FFTSize">
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7 changes: 7 additions & 0 deletions misc/extension_api_validation/4.5-stable/GH-114355.txt
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@@ -0,0 +1,7 @@
GH-114355
---------
Validate extension JSON: API was removed: classes/AudioEffectSpectrumAnalyzer/methods/set_tap_back_pos
Validate extension JSON: API was removed: classes/AudioEffectSpectrumAnalyzer/methods/get_tap_back_pos
Validate extension JSON: API was removed: classes/AudioEffectSpectrumAnalyzer/properties/tap_back_pos

Removed undocumented property that led to errors. Nothing was done to prevent breakage, since this was an undocumented property that made little change, and only made matters worse.
36 changes: 0 additions & 36 deletions servers/audio/effects/audio_effect_spectrum_analyzer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -99,8 +99,6 @@ static void smbFft(float *fftBuffer, long fftFrameSize, long sign)
}

void AudioEffectSpectrumAnalyzerInstance::process(const AudioFrame *p_src_frames, AudioFrame *p_dst_frames, int p_frame_count) {
uint64_t time = OS::get_singleton()->get_ticks_usec();

//copy everything over first, since this only really does capture
for (int i = 0; i < p_frame_count; i++) {
p_dst_frames[i] = p_src_frames[i];
Expand Down Expand Up @@ -143,10 +141,6 @@ void AudioEffectSpectrumAnalyzerInstance::process(const AudioFrame *p_src_frames
temporal_fft_pos = 0;
}
}

//determine time of capture
double remainder_sec = (temporal_fft_pos / mix_rate); //subtract remainder from mix time
last_fft_time = time - uint64_t(remainder_sec * 1000000.0);
}

void AudioEffectSpectrumAnalyzerInstance::_bind_methods() {
Expand All @@ -156,24 +150,8 @@ void AudioEffectSpectrumAnalyzerInstance::_bind_methods() {
}

Vector2 AudioEffectSpectrumAnalyzerInstance::get_magnitude_for_frequency_range(float p_begin, float p_end, MagnitudeMode p_mode) const {
if (last_fft_time == 0) {
return Vector2();
}
uint64_t time = OS::get_singleton()->get_ticks_usec();
float diff = double(time - last_fft_time) / 1000000.0 + base->get_tap_back_pos();
diff -= AudioServer::get_singleton()->get_output_latency();
float fft_time_size = float(fft_size) / mix_rate;

int fft_index = fft_pos;

while (diff > fft_time_size) {
diff -= fft_time_size;
fft_index -= 1;
if (fft_index < 0) {
fft_index = fft_count - 1;
}
}

int begin_pos = p_begin * fft_size / (mix_rate * 0.5);
int end_pos = p_end * fft_size / (mix_rate * 0.5);

Expand Down Expand Up @@ -216,7 +194,6 @@ Ref<AudioEffectInstance> AudioEffectSpectrumAnalyzer::instantiate() {
ins->mix_rate = AudioServer::get_singleton()->get_mix_rate();
ins->fft_count = (buffer_length / (float(ins->fft_size) / ins->mix_rate)) + 1;
ins->fft_pos = 0;
ins->last_fft_time = 0;
ins->fft_history.resize(ins->fft_count);
ins->temporal_fft.resize(ins->fft_size * 8); //x2 stereo, x2 amount of samples for freqs, x2 for input
ins->temporal_fft_pos = 0;
Expand All @@ -237,14 +214,6 @@ float AudioEffectSpectrumAnalyzer::get_buffer_length() const {
return buffer_length;
}

void AudioEffectSpectrumAnalyzer::set_tap_back_pos(float p_seconds) {
tapback_pos = p_seconds;
}

float AudioEffectSpectrumAnalyzer::get_tap_back_pos() const {
return tapback_pos;
}

void AudioEffectSpectrumAnalyzer::set_fft_size(FFTSize p_fft_size) {
ERR_FAIL_INDEX(p_fft_size, FFT_SIZE_MAX);
fft_size = p_fft_size;
Expand All @@ -258,14 +227,10 @@ void AudioEffectSpectrumAnalyzer::_bind_methods() {
ClassDB::bind_method(D_METHOD("set_buffer_length", "seconds"), &AudioEffectSpectrumAnalyzer::set_buffer_length);
ClassDB::bind_method(D_METHOD("get_buffer_length"), &AudioEffectSpectrumAnalyzer::get_buffer_length);

ClassDB::bind_method(D_METHOD("set_tap_back_pos", "seconds"), &AudioEffectSpectrumAnalyzer::set_tap_back_pos);
ClassDB::bind_method(D_METHOD("get_tap_back_pos"), &AudioEffectSpectrumAnalyzer::get_tap_back_pos);

ClassDB::bind_method(D_METHOD("set_fft_size", "size"), &AudioEffectSpectrumAnalyzer::set_fft_size);
ClassDB::bind_method(D_METHOD("get_fft_size"), &AudioEffectSpectrumAnalyzer::get_fft_size);

ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "buffer_length", PROPERTY_HINT_RANGE, "0.1,4,0.1,suffix:s"), "set_buffer_length", "get_buffer_length");
ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "tap_back_pos", PROPERTY_HINT_RANGE, "0.1,4,0.1"), "set_tap_back_pos", "get_tap_back_pos");
ADD_PROPERTY(PropertyInfo(Variant::INT, "fft_size", PROPERTY_HINT_ENUM, "256,512,1024,2048,4096"), "set_fft_size", "get_fft_size");

BIND_ENUM_CONSTANT(FFT_SIZE_256);
Expand All @@ -278,6 +243,5 @@ void AudioEffectSpectrumAnalyzer::_bind_methods() {

AudioEffectSpectrumAnalyzer::AudioEffectSpectrumAnalyzer() {
buffer_length = 2;
tapback_pos = 0.01;
fft_size = FFT_SIZE_1024;
}
4 changes: 0 additions & 4 deletions servers/audio/effects/audio_effect_spectrum_analyzer.h
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Expand Up @@ -54,7 +54,6 @@ class AudioEffectSpectrumAnalyzerInstance : public AudioEffectInstance {
int fft_count;
int fft_pos;
float mix_rate;
uint64_t last_fft_time;

protected:
static void _bind_methods();
Expand Down Expand Up @@ -82,7 +81,6 @@ class AudioEffectSpectrumAnalyzer : public AudioEffect {
public:
friend class AudioEffectSpectrumAnalyzerInstance;
float buffer_length;
float tapback_pos;
FFTSize fft_size;

protected:
Expand All @@ -92,8 +90,6 @@ class AudioEffectSpectrumAnalyzer : public AudioEffect {
Ref<AudioEffectInstance> instantiate() override;
void set_buffer_length(float p_seconds);
float get_buffer_length() const;
void set_tap_back_pos(float p_seconds);
float get_tap_back_pos() const;

void set_fft_size(FFTSize);
FFTSize get_fft_size() const;
Expand Down