Using speech synthesis in AGI apps

For some of my telephone apps, stringing together pre-recorded messages is a pain, and it’s not even useful for more dynamic content. This is how I got PHP to do sound output via festival whilst using the asterisk AGI.

First, I made a folder called agi in my /var/lib/asterisk/sounds/en/. This is where we will cache sound files.

This shell script makes a sound file with your text, and saves it in that directory:

echo "$1" | text2wave -otype ulaw -o /var/lib/asterisk/sounds/en/agi/$2.ulaw

For the PHP side, we just use MD5 to name the files based on their contents, and only run the shell script if no file has been created with the text we want.

In this project, $agi refers to an instance of PHP AGI. (highly recommended)

function sayNow($string, $escape = "") {
	global $agi;
	$sounds_path	= "/var/lib/asterisk/sounds/en/agi/";
	$agi_path	= "/var/lib/asterisk/agi-bin/"
	$fn = md5($string);
	$string = str_replace(""", "", $string);
	$string = str_replace(";", ",", $string);
	$string = str_replace("'", "", $string);
	$string = str_replace(""", " slash ", $string);
	if(!file_exists("$sounds_path$fn")) {
		system("$agi_path$common/ "$string" "$fn"");
	return $agi -> stream_file("$sounds_path$fn", $escape);

This makes sound output at least a million times easier. We use it like this:

$a = sayNow("Enter the number, then press hash");

That’s all there is to it. I should probably also set up a cron job to clear the sound files at the end of each week.