Should support Flite and PocketSphinx on Asterisk via UniMRCP Server

[benlangfeld]

Motivation

Flite and PocketSphinx are the only TTS and ASR engines available at zero cost for use with Asterisk via MRCP. They are supported via plugins to UniMRCP server and are installed on Telephony Dev Box.

Unfortunately Flite does not support SSML (plain text only) and PocketSphinx supports only JSGF grammars, not SRGS.

Changes required

• Plain text content of an SSML document must be extracted here
• SRGS grammars must be converted to JSGF here

Since Punchblock nor the UniMRCP client do not know what formats an engine supports prior to submitting a request to them, it would seem sensible for these manipulations to be implemented in the UniMRCP Server plugins such that they are transparent to the client side. These manipulations could be implemented using cspeech once it's ready.

Application impact

None.

[benlangfeld]

@bklang Comments appreciated.

[bklang]

Sounds entirely reasonable to me. I don't know how much work the JSGF->SRGS conversion would be, or how perfectly the capabilities overlap. Stripping SSML seems easy enough. I do like that we'll have an entry-level ASR+TTS option on Asterisk.

[benlangfeld]

The SRGS->JSGF conversion is already working in mod_rayo, and has been extracted to cspeech. Just waiting on that library to be completed...