OpenJTalk (open_jtalk_elixir v0.3.0)

Use Open JTalk from Elixir. This package builds a local open_jtalk CLI and, by default, bundles a UTF-8 dictionary and an HTS voice (you can disable this), exposing convenient functions:

OpenJTalk.say/2 — synthesize and play via a system audio player
OpenJTalk.to_wav_file/2 — synthesize text to a WAV file
OpenJTalk.to_wav_binary/2 — synthesize and return WAV bytes
OpenJTalk.Wav.concat_binaries/1 — merge multiple WAV binaries (same format)
OpenJTalk.Wav.concat_files/1 — merge multiple WAV files from paths (same format)

Install

Add the dependency to your mix.exs:

def deps do
  [
    {:open_jtalk_elixir, "~> 0.3"}
  ]
end

Then:

mix deps.get
mix compile

On first compile the project may download and build MeCab, HTS Engine API, and Open JTalk. By default it also downloads and bundles a UTF-8 dictionary and a Mei voice into priv/ (you can turn this off with OPENJTALK_BUNDLE_ASSETS=0).

Build requirements

You’ll need common build tools: gcc/g++, make, curl, tar, unzip. On macOS Xcode Command Line Tools are sufficient.

Optional environment flags (honored by the Makefile):

OPENJTALK_FULL_STATIC=1 — attempt a fully static open_jtalk (Linux only; requires static libstdc++)
OPENJTALK_BUNDLE_ASSETS=0|1 — whether to bundle dictionary/voice into priv/

Tested platforms

Host builds (compile and run on the same machine):

Linux x86_64
Linux aarch64
macOS 14 (arm64, Apple Silicon)

Cross-compile (host → target):

Linux x86_64 → Nerves rpi4 (aarch64)

Quick start

# play via system audio player (aplay/paplay/afplay/play)
OpenJTalk.say("元氣ですかあ 、元氣が有れば、なんでもできる")

Options

All synthesis calls accept the same options (values are clamped):

:timbre — voice color offset -0.8..0.8 (default 0.0)
:pitch_shift — semitones -24..24 (default 0)
:rate — speaking speed 0.5..2.0 (default 1.0)
:gain — output gain in dB (default 0)
:voice — path to a .htsvoice file (optional)
:dictionary — path to a directory containing sys.dic (optional)
:timeout — max runtime in ms (default 20_000)
:out — output WAV path (only for to_wav_file/2)

Concatenate WAVs

You can combine multiple WAVs (same format: channels/rate/bit depth/etc.) into one:

{:ok, a} = OpenJTalk.to_wav_binary("これは一つ目。")
{:ok, b} = OpenJTalk.to_wav_binary("これは二つ目。")
{:ok, c} = OpenJTalk.to_wav_binary("これは三つ目。")

{:ok, merged} = OpenJTalk.Wav.concat_binaries([a, b, c])
# or from files:
# {:ok, merged} = OpenJTalk.Wav.concat_files(["a.wav", "b.wav", "c.wav"])

Summary

Types

gain()

Output gain in dB. Typical useful range is about -20..20 (values are clamped).

info_entry()

Entry describing a component path and where it came from.

info_map()

Return type of info/0.

pitch_shift()

Pitch shift in semitones. Range: -24..24 (values are clamped).

playback_mode()

Audio playback mode

player_option()

Options accepted by playback functions.

rate()

Speaking rate multiplier. Range: 0.5..2.0 (values are clamped).

say_option()

Options accepted by say/2 (synth + playback + optional :out).

synth_option()

Options accepted by synthesis functions.

timbre()

Voice color adjustment. Range: -0.8..0.8 (values are clamped).

Functions

info()

Return useful information about the local Open J Talk setup.

play_wav_binary(wav_bytes, opts \\ [])

Play RIFF/WAV bytes already in memory (no temp files).

play_wav_file(path, opts \\ [])

Play a WAV from a file path. See play_wav_binary/2 for options.

say(text, opts \\ [])

Synthesize text with Open JTalk and play it.

to_wav_binary(text, opts \\ [])

Synthesize text and return RIFF/WAV bytes.

to_wav_file(text, opts \\ [])

Synthesize text to a WAV file. Respects :out when provided; otherwise creates a unique path in the system temp dir.

validate_options!(opts)

Validate options for synthesis and playback.