Initial commit

main.c

@@ -0,0 +1,166 @@
+#include <alsa/asoundlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <math.h>
+#include "synth.h"
+
+#define ALSA_CHK(stmt, msg) do { \
+    int alsa_chk_err = (stmt); \
+    if (alsa_chk_err < 0) { \
+        fprintf(stderr, "%s%s\n", msg, snd_strerror(alsa_chk_err)); \
+        return 1; \
+    } \
+} while (0)
+
+#define N_CHANNELS 1
+#define SAMPLE_RATE 44100
+#define PLAYBACK_LATENCY 50000 // 50 ms
+#define PLAYBACK_BUFFER_SIZE 512
+
+static int write_audio(snd_pcm_t *handle, const int16_t *buffer) {
+    snd_pcm_uframes_t offset = 0;
+
+    while (offset < PLAYBACK_BUFFER_SIZE) {
+        snd_pcm_sframes_t written = snd_pcm_writei(
+            handle, buffer + offset * N_CHANNELS,
+            PLAYBACK_BUFFER_SIZE - offset);
+
+        if (written < 0) {
+            int err = snd_pcm_recover(handle, (int)written, 1);
+            ALSA_CHK(err, "Could not write to alsa device: ");
+            continue;
+        }
+
+        if (written == 0) {
+            int err = snd_pcm_wait(handle, -1);
+            if (err < 0) {
+                err = snd_pcm_recover(handle, err, 1);
+                ALSA_CHK(err, "Could not write to alsa device: ");
+            }
+            continue;
+        }
+
+        offset += (snd_pcm_uframes_t)written;
+    }
+
+    return 0;
+}
+
+static int midi_open(snd_seq_t **seq_handle, int src_client, int src_port) {
+  int err = snd_seq_open(seq_handle, "default", SND_SEQ_OPEN_INPUT, SND_SEQ_NONBLOCK);
+  ALSA_CHK(err, "Error opening ALSA sequencer: ");
+
+  err = snd_seq_set_client_name(*seq_handle, "Midi Listener");
+  ALSA_CHK(err, "Error setting sequencer client name: ");
+
+  uint32_t caps = SND_SEQ_PORT_CAP_WRITE | SND_SEQ_PORT_CAP_SUBS_WRITE;
+  int in_port = snd_seq_create_simple_port(*seq_handle, "listen:in", caps, SND_SEQ_PORT_TYPE_APPLICATION);
+  ALSA_CHK(in_port, "Error creating sequencer port: ");
+
+  err = snd_seq_connect_from(*seq_handle, in_port, src_client, src_port);
+  ALSA_CHK(err, "Error connecting MIDI source: ");
+  return 0;
+}
+
+static float midi_note_to_freq(int midi) {
+    int note_offset = midi - 69;
+    return 440.0f * exp2f((float) note_offset / 12.0f);
+}
+
+static Waveform cycle_waveform(Waveform form) {
+    Waveform new_form = form + 1;
+    if (new_form > WAVE_TRIANGLE) {
+        new_form = WAVE_SINE;
+    }
+    const char *waveform_names[] = {"NONE", "SINE", "SQUARE", "SAW", "TRIANGLE"};
+    printf("Waveform changed to: %s\n", waveform_names[new_form]);
+    return new_form;
+}
+
+static int parse_port(int *src_client, int *src_port, const char *str) {
+    return sscanf(str, "%d:%d", src_client, src_port) == 2;
+}
+
+int main(int argc, const char** argv) {
+    if (argc < 2) {
+        fprintf(stderr, "Usage: %s 20:0\n", argv[0]);
+        return 1;
+    }
+
+    int src_client = 0;
+    int src_port = 0;
+    if (!parse_port(&src_client, &src_port, argv[1])) {
+        fprintf(stderr, "Unable to parse midi port %s\n", argv[1]);
+        return 1;
+    }
+    int err = 0;
+    snd_pcm_t *handle = 0;
+
+    // Init alsa audio
+    err = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0);
+    ALSA_CHK(err, "Could not open alsa device: ");
+    err = snd_pcm_set_params(handle, SND_PCM_FORMAT_S16_LE, SND_PCM_ACCESS_RW_INTERLEAVED, N_CHANNELS, SAMPLE_RATE, 1, PLAYBACK_LATENCY);
+    ALSA_CHK(err, "Could not set alsa params: ");
+
+    // Init alsa midi
+    snd_seq_t *seq_handle = 0;
+    err = midi_open(&seq_handle, src_client, src_port);
+    if (err) {
+        printf("Error initializing MIDI: %d\n", err);
+        return err;
+    }
+
+    // Main loop
+    Note note = {
+        .form = WAVE_SAW,
+        .attack_ms = 100.0f,
+        .release_ms = 50.0f
+    };
+    int16_t buf[PLAYBACK_BUFFER_SIZE] = {0};
+    for (;;) {
+        // Drain queued MIDI events
+        for (;;) {
+            snd_seq_event_t *ev = NULL;
+            int ret = snd_seq_event_input(seq_handle, &ev);
+            if (ret == -EAGAIN) {
+                break;
+            }
+            ALSA_CHK(ret, "Failed to read midi event: ");
+            if (!ev) {
+                continue;
+            }
+
+            switch (ev->type) {
+                case SND_SEQ_EVENT_NOTEON: {
+                    note.is_playing = ev->data.note.velocity != 0;
+                    note.freq = midi_note_to_freq(ev->data.note.note);
+                } break;
+                case SND_SEQ_EVENT_NOTEOFF: {
+                    note.is_playing = false;
+                } break;
+                case SND_SEQ_EVENT_CONTROLLER: {
+                    note.filter_cutoff = (float) ev->data.control.value / 64.0f;
+                    printf("filter cutoff: %f\n", note.filter_cutoff);
+                } break;
+                case SND_SEQ_EVENT_PGMCHANGE: {
+                    note.form = cycle_waveform(note.form);
+                } break;
+                default:
+                    printf("%d\n", ev->type);
+                    break;
+            }
+            snd_seq_free_event(ev);
+        }
+
+        play_note(&note, buf, PLAYBACK_BUFFER_SIZE);
+
+        if (write_audio(handle, buf) < 0) {
+            return 1;
+        }
+    }
+
+    snd_pcm_drain(handle); // wait for playback to finish (not stricty needed depending on requested latency)
+    snd_pcm_close(handle);
+    return 0;
+}