92 lines
3.4 KiB
C++
92 lines
3.4 KiB
C++
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// render_opl.cpp — render a MIDI file to WAV through OPL3 FM emulation
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// (libADLMIDI), i.e. the authentic Sound Blaster / AdLib sound. No
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// soundfont involved: pure FM synthesis, like the real 1993 silicon.
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//
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// Build: see build.sh in this directory.
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// Usage: render_opl in.mid out.wav seconds [volume_model]
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//
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// Volume models (the fun bit — they mimic real game sound drivers):
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// 0 auto 1 generic 2 NativeOPL3 (CMF/id-style) 3 DMX (Doom)
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// 4 APOGEE (Duke Nukem 3D) 5 9X 8 AIL (Another World era)
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// 10 HMI
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#include "adlmidi.h"
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#include <cstdio>
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#include <cstdlib>
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#include <algorithm>
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#include <vector>
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static void wr32(FILE *f, unsigned v) {
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unsigned char b[4] = {ADL_UInt8(v), ADL_UInt8(v >> 8), ADL_UInt8(v >> 16), ADL_UInt8(v >> 24)};
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fwrite(b, 1, 4, f);
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}
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static void wr16(FILE *f, unsigned v) {
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unsigned char b[2] = {ADL_UInt8(v), ADL_UInt8(v >> 8)};
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fwrite(b, 1, 2, f);
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}
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int main(int argc, char **argv) {
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if (argc < 4) {
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fprintf(stderr, "usage: render_opl in.mid out.wav seconds [volume_model]\n");
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return 2;
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}
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const long rate = 44100;
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double secs = atof(argv[3]);
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int model = (argc > 4) ? atoi(argv[4]) : 3; // default: DMX (Doom-ish)
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ADL_MIDIPlayer *adl = adl_init(rate);
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if (!adl) { fprintf(stderr, "adl_init failed\n"); return 1; }
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adl_setVolumeRangeModel(adl, model);
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adl_setNumChips(adl, 2); // two OPL3s: our arrangements are dense
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if (adl_openFile(adl, argv[1]) != 0) {
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fprintf(stderr, "cannot open %s: %s\n", argv[1], adl_errorString());
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adl_close(adl); return 1;
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}
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FILE *f = fopen(argv[2], "wb");
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if (!f) { fprintf(stderr, "cannot write %s\n", argv[2]); adl_close(adl); return 1; }
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// WAV header (sizes patched to actual bytes written at the end)
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const long data_off = 40;
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fwrite("RIFF", 1, 4, f); wr32(f, 0); fwrite("WAVE", 1, 4, f);
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fwrite("fmt ", 1, 4, f); wr32(f, 16); wr16(f, 1); wr16(f, 2);
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wr32(f, unsigned(rate)); wr32(f, unsigned(rate * 4)); wr16(f, 4); wr16(f, 16);
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fwrite("data", 1, 4, f); wr32(f, 0);
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std::vector<short> buf(2048 * 2);
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std::vector<short> all;
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int frames_done = 0, frames_total = int(secs * rate);
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while (frames_done < frames_total) {
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int n = frames_total - frames_done;
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if (n > 2048) n = 2048;
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if (adl_play(adl, n * 2, buf.data()) != 0) {
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all.insert(all.end(), buf.begin(), buf.begin() + n * 2);
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frames_done += n;
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} else {
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break; // end of sequence (or error; errorString empty at EOF)
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}
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}
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// Normalise: OPL FM runs quiet; bring the peak up to ~-17dBFS, capped
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// so we never amplify a near-silent track into hiss.
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int peak = 0;
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for (short s : all) peak = std::max(peak, std::abs(int(s)));
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double gain = (peak > 0 && peak < 24000) ? std::min(24000.0 / peak, 12.0) : 1.0;
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if (gain != 1.0) {
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for (short &s : all) {
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int v = int(s * gain);
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s = short(v > 32767 ? 32767 : (v < -32767 ? -32767 : v));
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}
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}
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fprintf(stderr, "peak %d, gain x%.1f\n", peak, gain);
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long bytes_written = long(all.size()) * 2;
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fwrite(all.data(), 2, all.size(), f);
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fflush(f);
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fseek(f, 4, SEEK_SET); wr32(f, unsigned(36 + bytes_written));
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fseek(f, data_off, SEEK_SET); wr32(f, unsigned(bytes_written));
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fclose(f);
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adl_close(adl);
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fprintf(stderr, "rendered %d frames of OPL3\n", frames_done);
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return 0;
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}
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