One of the biggest problems in the development of speech synthesis, and other areas of speech and language processing systems, is that there are a lot of simple well-known techniques lying around which can help you realise your goal. But in order to improve some part of the whole system it is necessary to have a whole system in which you can test and improve your part. Festival is intended as that whole system in which you may simply work on your small part to improve the whole. Without a system like Festival, before you could even start to test your new module you would need to spend significant effort to build a whole system, or adapt an existing one before you could start working on your improvements.
Festival is specifically designed to allow the addition of new modules, easily and efficiently, so that development need not get bogged down in re-implementing the wheel.
But there is another aspect of Festival which makes it more useful than simply an environment for researching into new synthesis techniques. It is a fully usable text-to-speech system suitable for embedding in other projects that require speech output. The provision of a fully working easy-to-use speech synthesizer in addition to just a testing environment is good for two specific reasons. First, it offers a conduit for our research, in that our experiments can quickly and directly benefit users of our synthesis system. And secondly, in ensuring we have a fully working usable system we can immediately see what problems exist and where our research should be directed rather where our whims take us.
These concepts are not unique to Festival. ATR’s CHATR system (black94) follows very much the same philosophy and Festival benefits from the experiences gained in the development of that system. Festival benefits from various pieces of previous work. As well as CHATR, CSTR’s previous synthesizers, Osprey and the Polyglot projects influenced many design decisions. Also we are influenced by more general programs in considering software engineering issues, especially GNU Octave and Emacs on which the basic script model was based.
Unlike in some other speech and language systems, software engineering is considered very important to the development of Festival. Too often research systems consist of random collections of hacky little scripts and code. No one person can confidently describe the algorithms it performs, as parameters are scattered throughout the system, with tricks and hacks making it impossible to really evaluate why the system is good (or bad). Such systems do not help the advancement of speech technology, except perhaps in pointing at ideas that should be further investigated. If the algorithms and techniques cannot be described externally from the program such that they can reimplemented by others, what is the point of doing the work?
Festival offers a common framework where multiple techniques may be implemented (by the same or different researchers) so that they may be tested more fairly in the same environment.
As a final word, we’d like to make two short statements which both achieve the same end but unfortunately perhaps not for the same reasons:
Good software engineering makes good research easier
But the following seems to be true also
If you spend enough effort on something it can be shown to be better than its competitors.