How to use RHVoice via Speech Dispatcher in Qt

I am trying to use RHVoice in my Qt C++ project on a Linux.

I installed RHVoice, and I struggled with its library RHVoice.h, which is provided by librhvoice-dev package, and so far, it seems like a dead end.

Then I found out that Speech-Dispatcher supports RHVoice module, and Qt Text To Speech supports Speech-Dispatcher, so it seemed like the proper way to use RHVoice in Qt.

But the Qt documentation says:

The speech-dispatcher engine does not support any engine specific parameters.

So I cannot make Speech-Dispatcher use RHVoice through Qt, and my question is basically how to work around this limitation?

Solution

One solution to this is to set RHVoice as the default synthesizer for Speech-Dispatcher, which can be done as follows:

Modify Speech-Dispatcher configuration by modifying the following files:

/usr/share/speech-dispatcher/conf/speechd.conf

/etc/speech-dispatcher/speechd.conf

If you want to change the configuration per-user only, editing the following file is enough:

~/.config/speech-dispatcher/speechd.conf

Change the DefaultModule to rhvoice as follows:

...
# -----OUTPUT MODULES CONFIGURATION-----
...
# The DefaultModule selects which output module is the default.  You
# must use one of the names of the modules loaded with AddModule.

DefaultModule rhvoice

save and close, and check if it works in your Qt Project, here's an example:

CMake:

cmake_minimum_required(VERSION 3.14)

project(RHVoiceSpeechD LANGUAGES CXX)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Core TextToSpeech)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Core TextToSpeech)

add_executable(RHVoiceSpeechD
  main.cpp
)
target_link_libraries(RHVoiceSpeechD Qt${QT_VERSION_MAJOR}::Core Qt${QT_VERSION_MAJOR}::TextToSpeech)

install(TARGETS RHVoiceSpeechD
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})

main.cpp:

#include <QCoreApplication>
#include <QTextToSpeech>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QTextToSpeech *tts = new QTextToSpeech();

    //set speechd as the engine if it is not the default engine
    tts->setEngine("speechd");

    //test it
    tts->say("I'm using RHVoice as a synthesizer");

    return a.exec();
}

Run this command in a terminal:

spd-say -o rhvoice "I'm using RHVoice as a synthesizer"

and compare the audio output with the one from your Qt project, they should sound the same if the previous steps worked, the default voice for RHVoice is "Alan".

Sources: