LA0 - PSG, SCC/SCC+, OPLL sound driver.

#include <la0.h> More...

Collaboration diagram for LA0 - PSG, SCC/SCC+, OPLL sound driver.:

Modules
	Open LA0 file image.
	Set a song in LA0 file to the decoder.
	Other LA0 specific APIs.

Files
file	la0.h
	The libmsx audio format 0 (LA0) decoder.

Variables
const AudioDecoder	LA0_BGM_DECODER
	LA0 BGM decoder.
const AudioDecoder	LA0_SFX_DECODER
	LA0 SFX decoder.

Detailed Description

#include <la0.h>

LA0 decoder is a decoder for the libmsx audio replayer.

la0.h provides LA0 decoder specific APIs. It is supposed to use with audio.h the libmsx audio replayer APIs.

LA0 decoder supports all functionality of the libmsx audio replayer.

• Supported sound chip :
  • PSG (AY-3-8910) x 1,
  • Konami SCC/SCC+ x 1,
  • MSX-MUSIC (OPLL/YM2413) x 1.
• Functionality :
  • NTSC (60Hz), PAL/SECAM (50Hz), auto detect and auto adjust.
  • Available to specify default playing frequency that the sound data author expecting.
  • Run-time replay frequency control.
  • Stop, Start, Pause, Resume.
  • Auto-repeat function for background music.
  • Playing sound effects (SFX) during playing background music (BGM).
  • Same file format for BGM and SFX.
  • VGM files to LA0 file conversion tool is bundled. vgm2la

Example
The following sample application la0_demo shows usecase of LA0 and the libmsx audio replayer.

// -*- coding: utf-8-unix -*-
/*
 * Copyright (c) 2021-2024 Daishi Mori (mori0091)
 *
 * This software is released under the MIT License.\n
 * See https://github.com/mori0091/libmsx/blob/main/LICENSE
 *
 * GitHub libmsx project\n
 * https://github.com/mori0091/libmsx
 */
#include <msx.h>
 
#include <screen.h>
#include <text.h>
 
#include <audio.h>
#include <audio_buf.h>
#include <audio_efx_amp.h>
 
#include <la0.h>
 
#include <stdio.h>
 
// current song number
uint8_t song_number = 255;
uint8_t number_of_songs;
uint8_t number_of_sfx;
static MemFile bgm;
static MemFile sfx;
 
// joypad state
uint8_t pressed;
uint8_t clicked;
 
void show_vsync_freq(void) {
  locate(0, 0);
  printf("VSYNC:%dHz  ", (int)msx_get_vsync_frequency());
}
 
void show_player_freq(void) {
  locate(0, 1);
  printf(" PLAY:%dHz  ", (int)audio_get_bgm_frequency());
}
 
void show_bgm_info(void) {
  locate(0, 2);
  printf("  BGM:%dHz (#%d/%d)   ",
         (int)la0_get_bgm_frequency(),
         (int)song_number+1,
         (int)number_of_songs);
  show_player_freq();
  locate(26, 1); printf("%5zu", (size_t)la0_get_bgm_total_samples());
  locate(26, 2); printf("%5zu", (size_t)la0_get_bgm_loop_samples());
}
 
void increase_player_freq(void) {
  uint8_t Hz = audio_get_bgm_frequency();
  if (Hz < 240) {
    audio_set_bgm_frequency(Hz + 1);
    show_player_freq();
  }
}
 
void decrease_player_freq(void) {
  uint8_t Hz = audio_get_bgm_frequency();
  if (10 < Hz) {
    audio_set_bgm_frequency(Hz - 1);
    show_player_freq();
  }
}
 
// void toggle_pause(void) {
//   locate(13, 10);
//   if (audio_is_paused()) {
//     // resume
//     audio_start();
//     print("     ");
//   }
//   else {
//     // pause
//     audio_pause();
//     print("PAUSE");
//   }
// }
 
void next_song(void) {
  if (song_number < number_of_songs - 1) {
    song_number++;
  }
  else {
    song_number = 0;
  }
  la0_set_bgm(song_number, &bgm);
  JIFFY = 0;
  show_bgm_info();
}
 
void prev_song(void) {
  if (0 < song_number) {
    song_number--;
  } else {
    song_number = number_of_songs - 1;
  }
  la0_set_bgm(song_number, &bgm);
  JIFFY = 0;
  show_bgm_info();
}
 
void show_psg_register_values(void) {
  for (uint8_t i = 0; i < 14; ++i) {
    locate(5, 4+i);
    uint8_t val = audio_buf_cache[0xb0+i];
    printx((uint16_t)(val >> 4));
    printx((uint16_t)(val & 15));
  }
}
 
void show_psg_registers(void) {
  locate(0, 4);
  for (uint8_t i = 0; i < 14; ++i) {
    printf("R#%02d\n", (int)i);
  }
  show_psg_register_values();
}
 
void update_joypad_state(void) {
  uint8_t joy = joypad_get_state(0);
  clicked = pressed & ~joy;
  pressed = joy;
}
 
static void play(void) {
  audio_play();                 // The libmsx audio replayer
  audio_efx_amp();              // Effector (amp)
}
 
void main(void) {
  screen1();
  color(15, 4, 7);
  cls();
 
  number_of_songs = la0_open_resource(&bgm, "bgm.la0");
  number_of_sfx = la0_open_resource(&sfx, "sfx.la0");
  srand(JIFFY);
 
  locate(0, 21);
  print("  LEFT/RIGHT  Select BGM\n");
  print("   UP/DOWN    Player Freq.\n");
  print("    SPACE     Sound effects\n");
 
  audio_init();
  set_vsync_handler(play);
 
  audio_set_repeat(true);
 
  await_vsync();
  show_vsync_freq();
  show_player_freq();
  show_psg_registers();
 
  for (;;) {
    await_vsync();
 
    locate(26, 0); printf("%5zu", (size_t)JIFFY);
    show_psg_register_values();
 
    if (!audio_is_playing_bgm()) {
      next_song();
    }
 
    // If the current song has a looped section, it repeats up to twice.
    if (2 <= la0_get_bgm_loop_counter()) {
      // Start fade-out, wait for it to complete, then stop the replayer.
      audio_efx_amp_fadeout(4);
      while (audio_efx_amp_get_fade()) {
        await_vsync();
      }
      audio_stop();
      // Reset the main volume, select the next song, and restart the replayer.
      audio_efx_amp_set_volume(15);
      next_song();
      audio_start();
    }
 
    update_joypad_state();
    if (clicked & VK_FIRE_0) {
      if (number_of_sfx) {
        la0_set_sfx(rand() % number_of_sfx, &sfx);
      }
      // else {
      //   toggle_pause();         // pause / resume
      // }
    }
    if (clicked & VK_RIGHT) {
      next_song();
    }
    if (clicked & VK_LEFT) {
      prev_song();
    }
    if (pressed & VK_UP) {
      increase_player_freq();
    }
    if (pressed & VK_DOWN) {
      decrease_player_freq();
    }
  }
}

See also

The API of the libmsx audio replayer.

Effectors for the libmsx audio replayer.

la0_demo sample application.

vgm2la VGM files to LA0 file conversion tool.

Variable Documentation

LA0_BGM_DECODER

const AudioDecoder LA0_BGM_DECODER

extern

LA0 BGM decoder.

LA0_SFX_DECODER

const AudioDecoder LA0_SFX_DECODER

extern

LA0 SFX decoder.