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[fluid-dev] Weird timing issues

From: David Cohoe
Subject: [fluid-dev] Weird timing issues
Date: Tue, 13 Jun 2017 22:52:23 -0700

For a C++ project I'm working on, I'm wanting to use fluidsynth to read from a midi file, write it to a buffer, then use another library to play the midi from that buffer.  However, for certain midis, the timing gets all messed up.  Here's some code that produces the problem:

#include <fluidsynth.h>

#include <iostream>
#include <fstream>
#include <vector>

const int SAMPLE_LENGTH = 44100;
const int CHANNEL_NUMBER = 2;
const int SECONDS = 30;

std::vector<int16_t> samples(SAMPLE_LENGTH*CHANNEL_NUMBER*SECONDS);

fluid_settings_t* settings;
fluid_synth_t* synth;
fluid_player_t* player;

int main(int argc, char* argv[])
    if (argc < 3) {
        std::cout << "Please input a soundfont and midi file.";
        return 1;
    settings = new_fluid_settings();
    synth = new_fluid_synth(settings);
    if (fluid_synth_sfload(synth, argv[1], 1) == FLUID_FAILED) {
        std::cerr << "Unable to open soundfount" << std::endl;
        return 1;
    player = new_fluid_player(synth);
    if (fluid_player_add(player, argv[2]) == FLUID_FAILED) {
        std::cerr << "Unable to open midi" << std::endl;
        return 1;
    if (fluid_player_play(player) == FLUID_FAILED) {
        std::cerr << "Unable to play midi" << std::endl;
        return 1;
    if (fluid_synth_write_s16(synth, SAMPLE_LENGTH*SECONDS, &samples[0], 0, 2, &samples[0], 1, 2) == FLUID_FAILED) {
        std::cerr << "Unable to write buffer" << std::endl;
        return 1;

    // Not what I actually want to do, but it will let you hear it straight from the buffer
    std::ofstream file("sound.raw", std::ios::binary);
    file.write((char*)&samples[0], samples.size() * 2);

    return 0;

Compile that, and run with "[program] [soundfont] [midi]", and it will output some raw audio data.  With certain midis, this data's timing is off.  I've attached two midis, "001-Battle01.mid" and "015-Theme04.mid".  For 001Battle01.mid, it outputs fine.  However, 015-Theme04.mid sound bad.  I've attached another file, sound.ogg, which shows what it sounds like.

I've been trying several different things for a while, but nothing seems to be working.  Can anybody help?  Thank you!

Attachment: 001-Battle01.mid
Description: MIDI audio

Attachment: 015-Theme04.mid
Description: MIDI audio

Attachment: sound.ogg
Description: audio/ogg

Attachment: prog.cpp
Description: Text Data

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