Fun With TTS (Voxin) And Ladspa

1 Executive Summary

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.

2 Going 64-Bit: Upgrading To Voxin 1.6

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.

3 Applying LADSPA Effects Processing To TTS

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

4 The Best Is Yet To Come …

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

5 Acknowledgements

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.