speech-dispatcher rate and volume settings for espeak 1.25

[Jonathan Duddington]

On 04 Jun, Hynek Hanke <hanke at brailcom.org> wrote:
>
> I´ll change the default espeak-generic.conf parameters for the new
> eSpeak range in the next version of speechd.

For eSpeak, a volume/amplitude value of 100 is "full volume".

However, eSpeak can use greater values than this to increase the
loudness.  If you increase the value above 100, eSpeak will apply audio
compression to prevent waveform clipping.  So the voice sounds louder,
but there will be some slight distortion, although this isn't too bad
at values below 200.

You can try using the command-line espeak command to show this effect,
and hear which is the best value for you.
   espeak -a200 "hello, this is a test"

The SSML speech markup language defines volume of 100 to be both the
maximum and also the default.  This seems strange.

eSpeak allows volume greater than the default.  A human can speak
(shout) at a greater volume than his default, and that may include some
"distortion".