Fun With TTS (Voxin) And Ladspa

Voxin 1.6 — AKA ViaVoice Outloud — no longer requires that the Emacspeak TTS server be built as a 32-bit binary. This means that installing Voxin on 64-bit systems is now significantly easier since you no longer need to install 32-bit versions of TCL, TCLX, and the dependencies needed by library libibmeci.so. In addition to easing the installation process, not needing 32-bit binaries means that the Emacspeak Outloud server can now take advantage of audio processing such as that provided by LADSPA.

1. Install Voxin-1.6 or later from Voxin.
2. Update Emacspeak from GitHub (this will be part of the next public release).
3. Rebuild the atcleci.so binary in the servers/linux-outloud directory:

cd servers/linux-outloud && make clean && make

If all goes well, you'll now have a 64-bit version of atcleci.so. You can now run the Outloud server as servers/outloud. In about a year's time, servers/32-outloud will move to servers/obsolete, as will the associated servers/32-speech-server and servers/ssh-32-outloud.

With a 64-bit build of atcleci.so in place, we can now call on installed LADSPA plugins to apply digital sound processing to TTS output. To experiment with the possibilities, see some of the virtual sound devices defined in servers/linux-outloud/asoundrc. Copy over that file to your ~/.asoundrc after updating it to match your sound setup — you'll likely need to change the default sound-card to match your setup. You can now set environment variable ALSA_DEFAULT to one of the tts_<effect> virtual devices — and have the Outloud server apply the specified LADSPA effect to the generated TTS. Here is an example:

cd servers 
(export ALSA_DEFAULT=tts_reverb; ./outloud)
tts_selftest

The possibilities are endless — ALSA with LADSPA provides a rich suite of audio processing possibilities.

I'd like to acknowledge Gilles Casse for his work over the years on ensuring that Linux users have access to good quality TTS. Outloud would have been dead a long time ago if it weren't for his continued efforts toward keeping the lights on. His newest creation, libvoxin that forms the crux of Voxin-1.6 is an excellent piece of engineering that is likely to help Outloud survive for the future on modern Linux distros. Note that Gilles is also the primary author of the Emacspeak ESpeak server.