Add 1-pole low-pass filter.

miniaudio.h

@@ -1662,10 +1662,23 @@ typedef struct
     ma_uint32 channels;
     ma_uint32 sampleRate;
     double cutoffFrequency;
-} ma_lpf_config;
+} ma_lpf_config, ma_lpf1_config;
 
 ma_lpf_config ma_lpf_config_init(ma_format format, ma_uint32 channels, ma_uint32 sampleRate, double cutoffFrequency);
 
+typedef struct
+{
+    ma_format format;
+    ma_uint32 channels;
+    ma_biquad_coefficient a;
+    ma_biquad_coefficient r1[MA_MAX_CHANNELS];
+} ma_lpf1;
+
+ma_result ma_lpf1_init(const ma_lpf1_config* pConfig, ma_lpf1* pLPF);
+ma_result ma_lpf1_reinit(const ma_lpf1_config* pConfig, ma_lpf1* pLPF);
+ma_result ma_lpf1_process_pcm_frames(ma_lpf1* pLPF, void* pFramesOut, const void* pFramesIn, ma_uint64 frameCount);
+ma_uint32 ma_lpf1_get_latency(ma_lpf1* pLPF);
+
 typedef struct
 {
     ma_biquad bq;   /* The low-pass filter is implemented as a biquad filter. */
@@ -5508,6 +5521,12 @@ static MA_INLINE double ma_cos(double x)
     return ma_sin((MA_PI*0.5) - x);
 }
 
+static MA_INLINE double ma_exp(double x)
+{
+    /* TODO: Implement custom exp(x). */
+    return exp(x);
+}
+
 static MA_INLINE double ma_log(double x)
 {
     /* TODO: Implement custom log(x). */
@@ -29324,6 +29343,140 @@ ma_lpf_config ma_lpf_config_init(ma_format format, ma_uint32 channels, ma_uint32
     return config;
 }
 
+
+ma_result ma_lpf1_init(const ma_lpf1_config* pConfig, ma_lpf1* pLPF)
+{
+    if (pLPF == NULL) {
+        return MA_INVALID_ARGS;
+    }
+
+    MA_ZERO_OBJECT(pLPF);
+
+    if (pConfig == NULL) {
+        return MA_INVALID_ARGS;
+    }
+
+    return ma_lpf1_reinit(pConfig, pLPF);
+}
+
+ma_result ma_lpf1_reinit(const ma_lpf1_config* pConfig, ma_lpf1* pLPF)
+{
+    double a;
+
+    if (pLPF == NULL || pConfig == NULL) {
+        return MA_INVALID_ARGS;
+    }
+
+    /* Only supporting f32 and s16. */
+    if (pConfig->format != ma_format_f32 && pConfig->format != ma_format_s16) {
+        return MA_INVALID_ARGS;
+    }
+
+    /* The format cannot be changed after initialization. */
+    if (pLPF->format != ma_format_unknown && pLPF->format != pConfig->format) {
+        return MA_INVALID_OPERATION;
+    }
+
+    /* The channel count cannot be changed after initialization. */
+    if (pLPF->channels != 0 && pLPF->channels != pConfig->channels) {
+        return MA_INVALID_OPERATION;
+    }
+
+    pLPF->format   = pConfig->format;
+    pLPF->channels = pConfig->channels;
+
+    a = ma_exp(-2 * MA_PI_D * pConfig->cutoffFrequency / pConfig->sampleRate);
+    if (pConfig->format == ma_format_f32) {
+        pLPF->a.f32 = (float)a;
+    } else {
+        pLPF->a.s32 = ma_biquad_float_to_fp(a);
+    }
+
+    return MA_SUCCESS;
+}
+
+static MA_INLINE void ma_lpf1_process_pcm_frame_f32(ma_lpf1* pLPF, float* pY, const float* pX)
+{
+    ma_uint32 c;
+    const float a = pLPF->a.f32;
+    const float b = 1 - a;
+    
+    for (c = 0; c < pLPF->channels; c += 1) {
+        float r1 = pLPF->r1[c].f32;
+        float x  = pX[c];
+        float y;
+
+        y = b*x + a*r1;
+
+        pY[c]           = y;
+        pLPF->r1[c].f32 = y;
+    }
+}
+
+static MA_INLINE void ma_lpf1_process_pcm_frame_s16(ma_lpf1* pLPF, ma_int16* pY, const ma_int16* pX)
+{
+    ma_uint32 c;
+    const ma_int32 a = pLPF->a.s32;
+    const ma_int32 b = ((1 << MA_BIQUAD_FIXED_POINT_SHIFT) - a);
+    
+    for (c = 0; c < pLPF->channels; c += 1) {
+        ma_int32 r1 = pLPF->r1[c].s32;
+        ma_int32 x  = pX[c];
+        ma_int32 y;
+
+        y = (b*x + a*r1) >> MA_BIQUAD_FIXED_POINT_SHIFT;
+
+        pY[c]           = (ma_int16)y;
+        pLPF->r1[c].s32 = (ma_int32)y;
+    }
+}
+
+ma_result ma_lpf1_process_pcm_frames(ma_lpf1* pLPF, void* pFramesOut, const void* pFramesIn, ma_uint64 frameCount)
+{
+    ma_uint32 n;
+
+    if (pLPF == NULL || pFramesOut == NULL || pFramesIn == NULL) {
+        return MA_INVALID_ARGS;
+    }
+
+    /* Note that the logic below needs to support in-place filtering. That is, it must support the case where pFramesOut and pFramesIn are the same. */
+
+    if (pLPF->format == ma_format_f32) {
+        /* */ float* pY = (      float*)pFramesOut;
+        const float* pX = (const float*)pFramesIn;
+
+        for (n = 0; n < frameCount; n += 1) {
+            ma_lpf1_process_pcm_frame_f32(pLPF, pY, pX);
+            pY += pLPF->channels;
+            pX += pLPF->channels;
+        }
+    } else if (pLPF->format == ma_format_s16) {
+        /* */ ma_int16* pY = (      ma_int16*)pFramesOut;
+        const ma_int16* pX = (const ma_int16*)pFramesIn;
+
+        for (n = 0; n < frameCount; n += 1) {
+            ma_lpf1_process_pcm_frame_s16(pLPF, pY, pX);
+            pY += pLPF->channels;
+            pX += pLPF->channels;
+        }
+    } else {
+        MA_ASSERT(MA_FALSE);
+        return MA_INVALID_ARGS; /* Format not supported. Should never hit this because it's checked in ma_biquad_init() and ma_biquad_reinit(). */
+    }
+
+    return MA_SUCCESS;
+}
+
+ma_uint32 ma_lpf1_get_latency(ma_lpf1* pLPF)
+{
+    if (pLPF == NULL) {
+        return 0;
+    }
+
+    return 1;
+}
+
+
 static MA_INLINE ma_biquad_config ma_lpf__get_biquad_config(const ma_lpf_config* pConfig)
 {
     ma_biquad_config bqConfig;

tests/test_filtering/ma_test_filtering_lpf.c

@@ -1,7 +1,119 @@
 
-ma_result test_lpf__f32(const char* pInputFilePath)
+ma_result test_lpf1__f32(const char* pInputFilePath)
 {
-    const char* pOutputFilePath = "output/lpf_f32.wav";
+    const char* pOutputFilePath = "output/lpf1_f32.wav";
+    ma_result result;
+    ma_decoder_config decoderConfig;
+    ma_decoder decoder;
+    drwav_data_format wavFormat;
+    drwav wav;
+    ma_lpf1_config lpfConfig;
+    ma_lpf1 lpf;
+    
+    decoderConfig = ma_decoder_config_init(ma_format_f32, 0, 0);
+    result = ma_decoder_init_file(pInputFilePath, &decoderConfig, &decoder);
+    if (result != MA_SUCCESS) {
+        return result;
+    }
+
+    lpfConfig = ma_lpf_config_init(decoder.outputFormat, decoder.outputChannels, decoder.outputSampleRate, 2000);
+    result = ma_lpf1_init(&lpfConfig, &lpf);
+    if (result != MA_SUCCESS) {
+        ma_decoder_uninit(&decoder);
+        return result;
+    }
+
+    wavFormat = drwav_data_format_from_minaudio_format(decoder.outputFormat, decoder.outputChannels, decoder.outputSampleRate);
+    if (!drwav_init_file_write(&wav, pOutputFilePath, &wavFormat, NULL)) {
+        ma_decoder_uninit(&decoder);
+        return MA_ERROR;
+    }
+
+    for (;;) {
+        ma_uint8 tempIn[4096];
+        ma_uint8 tempOut[4096];
+        ma_uint64 tempCapIn  = sizeof(tempIn)  / ma_get_bytes_per_frame(decoder.outputFormat, decoder.outputChannels);
+        ma_uint64 tempCapOut = sizeof(tempOut) / ma_get_bytes_per_frame(decoder.outputFormat, decoder.outputChannels);
+        ma_uint64 framesToRead;
+        ma_uint64 framesJustRead;
+
+        framesToRead = ma_min(tempCapIn, tempCapOut);
+        framesJustRead = ma_decoder_read_pcm_frames(&decoder, tempIn, framesToRead);
+
+        /* Filter */
+        ma_lpf1_process_pcm_frames(&lpf, tempOut, tempIn, framesJustRead);
+
+        /* Write to the WAV file. */
+        drwav_write_pcm_frames(&wav, framesJustRead, tempOut);
+
+        if (framesJustRead < framesToRead) {
+            break;
+        }
+    }
+
+    drwav_uninit(&wav);
+    return MA_SUCCESS;
+}
+
+ma_result test_lpf1__s16(const char* pInputFilePath)
+{
+    const char* pOutputFilePath = "output/lpf1_s16.wav";
+    ma_result result;
+    ma_decoder_config decoderConfig;
+    ma_decoder decoder;
+    drwav_data_format wavFormat;
+    drwav wav;
+    ma_lpf1_config lpfConfig;
+    ma_lpf1 lpf;
+    
+    decoderConfig = ma_decoder_config_init(ma_format_s16, 0, 0);
+    result = ma_decoder_init_file(pInputFilePath, &decoderConfig, &decoder);
+    if (result != MA_SUCCESS) {
+        return result;
+    }
+
+    lpfConfig = ma_lpf_config_init(decoder.outputFormat, decoder.outputChannels, decoder.outputSampleRate, 2000);
+    result = ma_lpf1_init(&lpfConfig, &lpf);
+    if (result != MA_SUCCESS) {
+        ma_decoder_uninit(&decoder);
+        return result;
+    }
+
+    wavFormat = drwav_data_format_from_minaudio_format(decoder.outputFormat, decoder.outputChannels, decoder.outputSampleRate);
+    if (!drwav_init_file_write(&wav, pOutputFilePath, &wavFormat, NULL)) {
+        ma_decoder_uninit(&decoder);
+        return MA_ERROR;
+    }
+
+    for (;;) {
+        ma_uint8 tempIn[4096];
+        ma_uint8 tempOut[4096];
+        ma_uint64 tempCapIn  = sizeof(tempIn)  / ma_get_bytes_per_frame(decoder.outputFormat, decoder.outputChannels);
+        ma_uint64 tempCapOut = sizeof(tempOut) / ma_get_bytes_per_frame(decoder.outputFormat, decoder.outputChannels);
+        ma_uint64 framesToRead;
+        ma_uint64 framesJustRead;
+
+        framesToRead = ma_min(tempCapIn, tempCapOut);
+        framesJustRead = ma_decoder_read_pcm_frames(&decoder, tempIn, framesToRead);
+
+        /* Filter */
+        ma_lpf1_process_pcm_frames(&lpf, tempOut, tempIn, framesJustRead);
+
+        /* Write to the WAV file. */
+        drwav_write_pcm_frames(&wav, framesJustRead, tempOut);
+
+        if (framesJustRead < framesToRead) {
+            break;
+        }
+    }
+
+    drwav_uninit(&wav);
+    return MA_SUCCESS;
+}
+
+ma_result test_lpf2__f32(const char* pInputFilePath)
+{
+    const char* pOutputFilePath = "output/lpf2_f32.wav";
     ma_result result;
     ma_decoder_config decoderConfig;
     ma_decoder decoder;
@@ -68,7 +180,17 @@ int test_entry__lpf(int argc, char** argv)
 
     pInputFilePath = argv[1];
     
-    result = test_lpf__f32(pInputFilePath);
+    result = test_lpf1__f32(pInputFilePath);
+    if (result != MA_SUCCESS) {
+        hasError = MA_TRUE;
+    }
+
+    result = test_lpf1__s16(pInputFilePath);
+    if (result != MA_SUCCESS) {
+        hasError = MA_TRUE;
+    }
+
+    result = test_lpf2__f32(pInputFilePath);
     if (result != MA_SUCCESS) {
         hasError = MA_TRUE;
     }