🐛 [BUG] Loud noise when switching FluidSynth soundfonts

[c0d3h4x0r]

Hardware and software

• mt32-pi version: v0.10.0
• Raspberry Pi model: Raspberry Pi 3 Model A+
• HATs: MiSTer mt32-pi
• USB devices: None
• MIDI host: MiSTer USER I/O port

Bug description

If you use the MiSTer OSD to change the SoundFont while the mt32-pi is playing music (over HDMI), there's a short, LOUD blast of noise that sounds like residual buffered audio data leftover from the previous SoundFont.

Steps to reproduce

1. Load the ao486 core in MiSTer with mt32-pi attached via (and powered by) USER I/O port and configured via the core's OSD to use FluidSynth mode. Make sure your mt32-pi has multiple different SoundFonts in place to choose from.
2. Using an MS-DOS 6.22 or 7.10 VHD, run any game (such as DOOM) configured to use General MIDI (port 330h) for the music.
3. Let the demo start playing so that background music is playing on the mt32-pi.
4. While the music is playing, use the core's OSD to change to the next SoundFont.

Expected behavior

No loud garbage noise when switching among SoundFonts or when switching back and forth between Munt and FluidSynth modes.

Configuration file

<

#                                  ________    _______                      __
#                         __      /_____   `. /____   `.                   /__`
#     ____   ____     __/  /____  _______)  / ______)  / ____  ______      __
#   /   __ v  __  `./__   _____//_____    < /   _____. /____//   ___  `. /  /
#  /  /  /  /  /  /   /  /____  _______)  //  /______       /  /____/  //  .__
# /__/  /__/  /__/    \______//_________. /_________/      /   ______.  \____/
# /////////////////////////////////////////////////////// /  / //// /// // /
#                                                         ```
# mt32-pi.cfg: mt32-pi configuration file.
# Default options are marked with an asterisk (*).

# -----------------------------------------------------------------------------
# System options
# -----------------------------------------------------------------------------
[system]

# Enable or disable verbose startup and error output.
#
# When enabled, outputs more information to the LCD when starting up, and when
# MIDI/UART errors are detected.
#
# This also may hide the boot logo on smaller graphical displays.
#
# Values: on, off*
verbose = off

# Set the default synthesizer to be made active on startup.
#
# If the default synthesizer is unavailable (e.g. missing ROMs or SoundFonts),
# the first working synth is made active.
#
# Values: mt32*, soundfont
#
# mt32:      Use mt32emu (Munt) for Roland MT-32 emulation
# soundfont: Use FluidSynth for SoundFont synthesis
default_synth = soundfont

# Enable or disable support for USB devices.
#
# Disable this to speed up boot time if you are not using any USB devices.
#
# Values: on*, off
usb = on

# Set the I2C baud rate/clock speed for all peripherals (Hz).
#
# Most peripherals will work fine at the default speed (400KHz "fast mode"),
# but larger LCD/OLED displays (e.g. 4-line I2C HD44780 and 64 pixel high
# SSD1306) won't be able to refresh at 60FPS at the default setting.
#
# Try increasing this value to 1000000 (1MHz) for a smoother LCD refresh rate.
# If your display doesn't work, try backing off the speed 100KHz at a time
# until it does.
#
# Values: 100000-1000000 (400000*)
i2c_baud_rate = 400000

# Set the timeout for power saving mode (seconds).
#
# After the specified number of seconds of silence, the CPU clock speed will be
# reduced, the audio device will be stopped, and and the LCD's backlight will
# be turned off to save energy (certain I2C displays only).
#
# Any MIDI activity will instantly bring the system out of power saving mode.
#
# If set to 0, power saving mode is disabled.
#
# Values: 0-3600 (300*)
power_save_timeout = 60

# -----------------------------------------------------------------------------
# MIDI options
# -----------------------------------------------------------------------------
[midi]

# Set the baud rate used for GPIO MIDI.
#
# For connecting to standard MIDI devices (i.e. via DIN cable), this should be
# left at the default rate of 31250.
#
# For connecting to PCs, set this to match the baud rate of the other host.
# SoftMPU's serial MIDI mode, for example, uses a baud rate of 38400.
#
# Values: 300-4000000 (31250*)
gpio_baud_rate = 31250

# Enable or disable software "MIDI thru" on the GPIO Tx pin.
#
# When enabled, all data received via the GPIO Rx pin will be re-transmitted
# verbatim on the Tx pin. This may be useful for debugging or for passing MIDI
# data through to another synth.
#
# Values: on, off*
gpio_thru = off

# Set the baud rate used for USB serial MIDI.
#
# The same considerations from the gpio_baud_rate setting above apply here.
# The default value is a PC baud rate and matches SoftMPU's serial MIDI mode.
#
# The range of valid baud rates may vary depending on the chipset of your USB
# serial device, so the range of values suggested below may actually be greater.
#
# Values: 9600-115200 (38400*)
usb_serial_baud_rate = 38400

# -----------------------------------------------------------------------------
# Audio options
# -----------------------------------------------------------------------------
[audio]

# Select audio output device.
#
# Values: pwm*, i2s
#
# pwm: Use the headphone jack
# hdmi: Use the HDMI port
# i2s: Use an I2S DAC
output_device = i2s

# Sample rate of audio output (Hz).
#
# mt32emu uses an internal sample rate of 32000Hz (just like the real hardware)
# which is then resampled to this value.
#
# FluidSynth renders at this sample rate directly.
#
# Values: 32000-192000 (48000*)
sample_rate = 48000

# Set audio rendering chunk size (samples).
#
# A single stereo frame of audio has two samples, and so this value is double
# the number of frames per chunk.
# The smaller the chunk size, the lower the latency, but too low a value will
# cause underruns (distortion artifacts).
#
# Latency is a function of chunk size and sample rate, for example:
# 256 samples / 2 channels / 48000Hz * 1000ms = 2.67ms of latency.
# See documentation for recommended values for various Raspberry Pi models.
#
# The minimum value varies depending on audio output device.
# For PWM, the minimum is 2, for I2S the minimum is 32.
# For HDMI, the minimum is 384, and will be rounded to the nearest multiple of
# 384.
#
# Values: 2-2048 (256*)
chunk_size = 256

# Set address (hexadecimal) of I2C DAC control interface.
#
# This will be used for the initialization sequence (see below) if enabled.
# You can find the address of your DAC by using the i2cdetect utility in Linux.
#
# Values: 00-80 (4c*)
i2c_dac_address = 4c

# Select an initialization sequence for the DAC.
#
# Some DACs require some initialization commands to be sent via I2C before they
# will produce any sound.
#
# Values: none*, pcm51xx
#
# pcm51xx: for DACs based on PCM5121 or similar (e.g. PCM5141, PCM5242)
i2c_dac_init = none

# -----------------------------------------------------------------------------
# Control options
# -----------------------------------------------------------------------------
[control]

# Set the physical control scheme.
#
# See documentation for GPIO pinouts/wiring details.
#
# Values: none*, simple_buttons, simple_encoder
#
# none:           No physical controls
# simple_buttons: Simple 4-button scheme
# simple_encoder: Simple 2-button + rotary encoder scheme
scheme = simple_buttons

# Set the rotary encoder type (if used by control scheme).
#
# Different rotary encoders may complete different fractions of a Gray-code
# cycle per detent ("click").
#
# If four clicks are needed for a single movement, try "quarter".
# If two clicks are needed for a single movement, try "half".
#
# Values: quarter, half, full*
encoder_type = full

# Reverse the rotary encoder direction (if used by control scheme).
#
# Some rotary encoders may have their CLK/DAT signals swapped, resulting in
# a reversed rotation direction.
#
# Use this option to correct the direction.
#
# Values: on, off*
encoder_reversed = off

# Enable or disable the I2C MiSTer control interface.
#
# If using mt32-pi with a MiSTer FPGA system and custom hardware to interface
# with MiSTer's User Port, enable this option to allow controlling mt32-pi via
# the MiSTer's on-screen display.
#
# Values: on, off*
mister = on

# Set the timeout for switching SoundFonts (seconds).
#
# When switching SoundFonts using the physical button, there is a short delay
# before loading begins. This option allows you to set the number of seconds to
# wait before loading.
#
# Values: 0-3600 (3*)
switch_timeout = 1

# -----------------------------------------------------------------------------
# MT-32 emulator options
# -----------------------------------------------------------------------------
[mt32emu]

# Set gain factor applied to synthesizer output channels.
#
# This is independent of the master volume that can be set via MIDI SysEx or
# the volume knob.
#
# Values: 0.0-256.0 (1.0*)
gain = 0.85

# Set gain factor applied to reverb wet output channels.
#
# Values: 0.0-infinity (1.0*)
reverb_gain = 0.85

# Select quality level for the resampler.
#
# If set to none, audio output will sound wrong unless you set the sample rate
# option to 32000Hz, which is the MT-32's native sample rate.
#
# Values: none, fastest, fast, good*, best
resampler_quality = best

# Select initial MIDI channel assignment.
#
# The MT-32 uses an unusual MIDI channel assignment by default. On a real MT-32
# this is set using a button combination. Use this option to change the initial
# channel assignment on startup.
#
# Values: standard*, alternate
#
# standard:  Parts 1-8 = MIDI channels 2-9, Rhythm part = MIDI channel 10
# alternate: Parts 1-8 = MIDI channels 1-8, Rhythm part = MIDI channel 10
midi_channels = standard

# Select initial ROM set to use.
#
# If multiple ROM sets are available, this option determines which set to use
# on startup. If the ROM set specified here is unavailable, the first available
# set is used instead.
#
# Values: old*, new, cm32l
rom_set = cm32l

# Set whether the stereo channels should be swapped or not.
#
# The MT-32 interprets values for MIDI CC#10 (panpot) differently to later
# synthesizers, which means that 0 = right and 127 = left; the opposite of what
# is stated in the most recent versions of the MIDI specification.
#
# Enable this option to swap the channels and make MT-32 mode's panning
# behavior match the behavior of SoundFont mode. Note that this can also be
# switched at runtime with a custom SysEx command.
#
# Values: on, off*
reversed_stereo = off

# -----------------------------------------------------------------------------
# SoundFont synthesizer options
# -----------------------------------------------------------------------------
[fluidsynth]

# Set the initial SoundFont to use.
#
# If multiple SoundFonts are available, this option determines which SoundFont
# to use on startup.
#
# On startup, the "soundfonts" directory is scanned for valid SoundFonts, which
# are added to a list and sorted into alphabetical order.
#
# This setting is a zero-indexed offset into that list (i.e. 0 is the first,
# 1, is the second, and so on).
#
# If the index specified is unavailable, the first available SoundFont will be
# used.
#
# Values: 0-255 (0*)
soundfont = 0

# Set the master volume gain.
#
# The default is a low value to avoid clipping when many notes are playing at
# once.
#
# The value should be a decimal value between 0.0 and 10.0. Values outside this
# range will be clamped.
#
# Values: 0.0-10.0 (0.2*)
gain = 0.35

# Set the maximum number of voices that can be played simultaneously.
#
# Depending on the complexity of your SoundFont, you may need to reduce this
# value to prevent audio buffer underruns (distortion) when playing music
# featuring lots of notes being played at once.
#
# On the other hand, you may want to try raising this value if your Pi is
# being run overclocked or has a more powerful CPU (e.g. Pi 4/CM4).
#
# N.B. larger file size of the SoundFont does not imply higher CPU usage.
# SoundFonts that use more real-time effects (modulators) are more likely to
# require a reduction in polyphony.
#
# Values: 1-65535 (200*)
polyphony = 256

# The following settings set the default parameters for FluidSynth's reverb and
# chorus effects.
#
# Each setting can be overridden on a per-SoundFont basis by adding extra
# sections, e.g. [fluidsynth.soundfont.x], where x is the zero-based index of
# the SoundFont. See the next section for an example.
#
# Full descriptions and valid value ranges for each setting can be found in the
# FluidSynth documentation: https://www.fluidsynth.org/api/fluidsettings.xml
reverb = on
reverb_damping = 0.20
reverb_level = 0.5
reverb_room_size = 0.7
reverb_width = 0.75

chorus = on
chorus_depth = 4.5
chorus_level = 0.5
chorus_voices = 3
chorus_speed = 0.35


[fluidsynth.soundfont.1]
reverb_damping = 0.40
reverb_level = 0.15
reverb_room_size = 0.7
reverb_width = 0.75


[fluidsynth.soundfont.2]
reverb_level = 0.25


# -----------------------------------------------------------------------------
# LCD/OLED display options
# -----------------------------------------------------------------------------
[lcd]

# Select LCD driver.
#
# Note that LCDs connected via I2C, you must also set the correct address for
# your device via the i2c_lcd_address option. Consult its datasheet, or see
# our documentation for tested models and their configurations.
#
# Values: none*, hd44780_4bit, hd44780_i2c, sh1106_i2c, ssd1306_i2c
#
# none:         No LCD
# hd44780_4bit: Hitachi HD44780 or compatible (e.g. WS0010, RS0010) character
#               LCD connected to GPIO pins in 4-bit mode (see documentation for
#               pinout)
# hd44780_i2c:  As above, but using an I2C "backpack"
# sh1106_i2c:   Small I2C-based OLED graphical display (usually 1.3")
# ssd1306_i2c:  Small I2C-based OLED graphical display (usually 0.96")
type = ssd1306_i2c

# Set the width of the LCD.
#
# If the display is a character display, this value is measured in characters.
# Otherwise, for a graphical display, this is measured in pixels.
#
# Note that not all dimension settings are valid; see documentation for valid
# configurations for each LCD driver.
#
# Values: 20-128 (128*)
width = 128

# Set the height of the LCD.
#
# Same characters vs. pixels considerations as for width.
#
# Values: 2-64 (32*)
height = 64

# Set address (hexadecimal) of I2C LCD.
#
# This will be used to communicate with LCDs connected via the I2C bus.
#
# Values: 00-80 (3c*)
i2c_lcd_address = 3c

# Rotate the display output (graphical LCDs only).
#
# Some graphical displays support rotation. Use this option if you need to turn
# the display around.
#
# Values: normal*, inverted
#
# normal:   No rotation
# inverted: The display output is upside down
rotation = normal

# -----------------------------------------------------------------------------
# Network options
# -----------------------------------------------------------------------------
[network]

# Select the network mode.
#
# For setting your Wi-Fi SSID and encryption key, see wpa_supplicant.conf.
# Note that if using Ethernet on a Raspberry Pi 3B/3B+, USB must be enabled.
#
# off:      Disable networking
# ethernet: Enable using the Ethernet interface
# wifi:     Enable using the the Wi-Fi interface
#
# Values: off*, ethernet, wifi
mode = wifi

# Enable or disable DHCP for configuring the network.
#
# If disabled, the manual settings below will be used to configure your network
# interface instead.
#
# Values: on*, off
dhcp = on

# Manual settings for configuring the network interface.
#
# These settings will be ignored if DHCP is enabled.
#
# Values: correctly-formatted IP address/subnet mask, e.g. AAA.BBB.CCC.DDD
#         (four numbers in the range 0-255 separated by periods)
ip_address = 192.168.1.100
subnet_mask = 255.255.255.0
default_gateway = 192.168.1.1
dns_server = 192.168.1.1

# Set the network hostname.
#
# Values: a valid hostname using ASCII letters 'a' to 'z', digits 0-9, and
#         hyphens (*mt32-pi)
hostname = mt32-pi

# Enable or disable the RTP-MIDI/AppleMIDI server.
#
# This allows you to send MIDI data to mt32-pi over the network using macOS'
# built-in network MIDI features, or rtpMIDI by Tobias Erichsen on Windows.
#
# Values: on*, off
rtp_midi = on

# Enable or disable the embedded FTP server.
#
# This FTP server is a very basic implementation which DOES NOT feature any kind
# of transport layer security/encryption. Therefore, you should NOT enable this
# feature on a public network or expose the Raspberry Pi to the Internet.
#
# The FTP server should be considered a convenience feature only, for performing
# updates and configuration changes without having to replace the SD card.
#
# Values: on, off*
ftp = on

# Set the FTP server username and password.
#
# Values: any ASCII string (*mt32-pi)
ftp_username = mt32-pi
ftp_password = p4ssw0rd!

Videos/audio recordings

I can provide a short video later if needed.

Additional information

n/a

[dwhinham]

What's happening here is that disk I/O blocks everything else, and the incoming MIDI gets buffered up, then instantly dumped on the synth when disk I/O is done, i.e. you might get a few dozen Note-Ons all at once.

Should be an easy fix, I can just clear all the MIDI buffers after a SoundFont switch is done.

N.B. you shouldn't really be doing this. All the instruments and parameters are reset on switching and you'll be treated to an orchestra of pianos if you're hopping betweens synths and SoundFonts while a song is playing. This is by-design and won't be fixed.

[c0d3h4x0r]

Understood about the otherwise problematic aspect of switching SoundFonts during playback. But that, unlike the loud noise glitch, doesn't risk blowing out my ears or speakers. Sent via Outlook for iOS<https://aka.ms/o0ukef>

…

________________________________ From: Dale Whinham ***@***.***> Sent: Thursday, March 3, 2022 2:51:47 AM To: dwhinham/mt32-pi ***@***.***> Cc: Keith F. Kelly ***@***.***>; Author ***@***.***> Subject: Re: [dwhinham/mt32-pi] 🐛 [BUG] Loud noise when switching FluidSynth soundfonts (Issue #247) What's happening here is that disk I/O blocks everything else, and the incoming MIDI gets buffered up, then instantly dumped on the synth when disk I/O is done, i.e. you might get a few dozen Note-Ons all at once. Should be an easy fix, I can just clear all the MIDI buffers after a SoundFont switch is done. N.B. you shouldn't really be doing this. All the instruments and parameters are reset on switching and you'll be treated to an orchestra of pianos if you're hopping betweens synths and SoundFonts while a song is playing. This is by-design and won't be fixed. — Reply to this email directly, view it on GitHub<https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fdwhinham%2Fmt32-pi%2Fissues%2F247%23issuecomment-1057920182&data=04%7C01%7C%7Cd2e7a363390b44d78d5308d9fd03d0d4%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637819015100883553%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=GeCf%2Fsqx9KnDh79piCYF33absPd7U8MFm1GjkTlnw00%3D&reserved=0>, or unsubscribe<https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fnotifications%2Funsubscribe-auth%2FAF2EYJEYFBWT7U4354WSPUDU6CKUHANCNFSM5PYM5HKQ&data=04%7C01%7C%7Cd2e7a363390b44d78d5308d9fd03d0d4%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637819015100883553%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=dtsyjE%2FO%2FwzxANOsb7zGBvwjAvtPyjxVNeuDWcDPTQ0%3D&reserved=0>. Triage notifications on the go with GitHub Mobile for iOS<https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fapps.apple.com%2Fapp%2Fapple-store%2Fid1477376905%3Fct%3Dnotification-email%26mt%3D8%26pt%3D524675&data=04%7C01%7C%7Cd2e7a363390b44d78d5308d9fd03d0d4%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637819015100883553%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=V%2BDOEKTcJ9NtS7ITUMYlLAL0I3CSh7RBeHS2bJJVtJQ%3D&reserved=0> or Android<https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fplay.google.com%2Fstore%2Fapps%2Fdetails%3Fid%3Dcom.github.android%26referrer%3Dutm_campaign%253Dnotification-email%2526utm_medium%253Demail%2526utm_source%253Dgithub&data=04%7C01%7C%7Cd2e7a363390b44d78d5308d9fd03d0d4%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637819015100883553%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=rYsKXXxJaBQHtiQ%2B%2BVKpeUS9aZ6gkQS37w7zaBtlA94%3D&reserved=0>. You are receiving this because you authored the thread.Message ID: ***@***.***>