audio/filters/source/main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
 
#include <3ds.h>
 
#define SAMPLERATE 22050
#define SAMPLESPERBUF (SAMPLERATE / 30)
#define BYTESPERSAMPLE 4
 
#define ARRAY_SIZE(array) (sizeof(array)/sizeof(array[0]))
 
// audioBuffer is stereo PCM16
void fill_buffer(void* audioBuffer, size_t offset, size_t size, int frequency) {
 u32* dest = (u32*) audioBuffer;
 
 for (int i = 0; i < size; i++) {
 // This is a simple sine wave, with a frequency of `frequency` Hz, and an amplitude 30% of maximum.
 s16 sample = 0.3 * 0x7FFF * sin(frequency * (2 * M_PI) * (offset + i) / SAMPLERATE);
 
 // Stereo samples are interleaved: left and right channels.
 dest[i] = (sample << 16) | (sample & 0xffff);
 }
 
 DSP_FlushDataCache(audioBuffer, size);
}
 
int main(int argc, char **argv) {
 gfxInitDefault();
 
 PrintConsole topScreen;
 consoleInit(GFX_TOP, &topScreen);
 consoleSelect(&topScreen);
 
 printf("libctru filtered streamed audio\n");
 
 u32* audioBuffer = (u32*) linearAlloc(SAMPLESPERBUF * BYTESPERSAMPLE * 2);
 
 bool fillBlock = false;
 
 ndspInit();
 
 ndspSetOutputMode(NDSP_OUTPUT_STEREO);
 
 ndspChnSetInterp(0, NDSP_INTERP_LINEAR);
 ndspChnSetRate(0, SAMPLERATE);
 ndspChnSetFormat(0, NDSP_FORMAT_STEREO_PCM16);
 
 // Output at 100% on the first pair of left and right channels.
 
 float mix[12];
 memset(mix, 0, sizeof(mix));
 mix[0] = 1.0;
 mix[1] = 1.0;
 ndspChnSetMix(0, mix);
 
 // Note Frequencies
 
 int notefreq[] = {
 220,
 440, 880, 1760, 3520, 7040,
 14080,
 7040, 3520, 1760, 880, 440
 };
 
 int note = 4;
 
 // Filters
 
 const char* filter_names[] = {
 "None",
 "Low-Pass",
 "High-Pass",
 "Band-Pass",
 "Notch",
 "Peaking"
 };
 
 int filter = 0;
 
 // We set up two wave buffers and alternate between the two,
 // effectively streaming an infinitely long sine wave.
 
 ndspWaveBuf waveBuf[2];
 memset(waveBuf,0,sizeof(waveBuf));
 waveBuf[0].data_vaddr = &audioBuffer[0];
 waveBuf[0].nsamples = SAMPLESPERBUF;
 waveBuf[1].data_vaddr = &audioBuffer[SAMPLESPERBUF];
 waveBuf[1].nsamples = SAMPLESPERBUF;
 
 size_t stream_offset = 0;
 
 fill_buffer(audioBuffer,stream_offset, SAMPLESPERBUF * 2, notefreq[note]);
 
 stream_offset += SAMPLESPERBUF;
 
 ndspChnWaveBufAdd(0, &waveBuf[0]);
 ndspChnWaveBufAdd(0, &waveBuf[1]);
 
 printf("Press up/down to change tone frequency\n");
 printf("Press left/right to change filter\n");
 printf("\x1b[6;1Hnote = %i Hz ", notefreq[note]);
 printf("\x1b[7;1Hfilter = %s ", filter_names[filter]);
 
 while(aptMainLoop()) {
 
 gfxSwapBuffers();
 gfxFlushBuffers();
 gspWaitForVBlank();
 
 hidScanInput();
 u32 kDown = hidKeysDown();
 
 if (kDown & KEY_START)
 break; // break in order to return to hbmenu
 
 if (kDown & KEY_DOWN) {
 note--;
 if (note < 0) {
 note = ARRAY_SIZE(notefreq) - 1;
 }
 printf("\x1b[6;1Hnote = %i Hz ", notefreq[note]);
 } else if (kDown & KEY_UP) {
 note++;
 if (note >= ARRAY_SIZE(notefreq)) {
 note = 0;
 }
 printf("\x1b[6;1Hnote = %i Hz ", notefreq[note]);
 }
 
 bool update_params = false;
 if (kDown & KEY_LEFT) {
 filter--;
 if (filter < 0) {
 filter = ARRAY_SIZE(filter_names) - 1;
 }
 update_params = true;
 } else if (kDown & KEY_RIGHT) {
 filter++;
 if (filter >= ARRAY_SIZE(filter_names)) {
 filter = 0;
 }
 update_params = true;
 }
 
 if (update_params) {
 printf("\x1b[7;1Hfilter = %s ", filter_names[filter]);
 switch (filter) {
 default:
 ndspChnIirBiquadSetEnable(0, false);
 break;
 case 1:
 ndspChnIirBiquadSetParamsLowPassFilter(0, 1760.f, 0.707f);
 break;
 case 2:
 ndspChnIirBiquadSetParamsHighPassFilter(0, 1760.f, 0.707f);
 break;
 case 3:
 ndspChnIirBiquadSetParamsBandPassFilter(0, 1760.f, 0.707f);
 break;
 case 4:
 ndspChnIirBiquadSetParamsNotchFilter(0, 1760.f, 0.707f);
 break;
 case 5:
 ndspChnIirBiquadSetParamsPeakingEqualizer(0, 1760.f, 0.707f, 3.0f);
 break;
 }
 }
 
 if (waveBuf[fillBlock].status == NDSP_WBUF_DONE) {
 fill_buffer(waveBuf[fillBlock].data_pcm16, stream_offset, waveBuf[fillBlock].nsamples, notefreq[note]);
 ndspChnWaveBufAdd(0, &waveBuf[fillBlock]);
 stream_offset += waveBuf[fillBlock].nsamples;
 fillBlock = !fillBlock;
 }
 }
 
 ndspExit();
 
 linearFree(audioBuffer);
 
 gfxExit();
 return 0;
}