Page 356 - Asterisk™: The Future of Telephony

Speech recognition can actually work very well, but unfortunately this is generally true
only if you provide it with the right conditions—and the right conditions are not those
found on a telephone network. Even a perfect PSTN connection is considered to be at
the lowest acceptable limit for accurate speech recognition. Add in compressed and
lossy VoIP connections, or a cell phone, and you will discover far more limitations than
uses.

Asterisk now has an entire speech API so that outside companies (or even open source
projects) can tie their speech recognition engines into Asterisk. One company that has
done this is LumenVox. By using its speech recognition engine along with Asterisk, you
can make voice-driven menus and IVR systems in record time! For more information,
see http://www.lumenvox.com.

High-Fidelity Voice

As we gain access to more and more bandwidth, it becomes less and less easy to un-
derstand why we still use low-fidelity codecs. Many people do not realize that Skype
uses a higher fidelity than a telephone; it’s a large part of the reason why Skype has a
reputation for sounding so good.

If you were ever to phone CNN, wouldn’t you love to hear James Earl Jones’s mellif-
luous voice saying “This is CNN,” instead of some tinny electronic recording? And if
*
you think Allison Smith sounds good through the phone, you should hear her in per-
son!
In the future, we will expect, and get, high-fidelity voice though our communications
equipment.
Beginning in Asterisk 1.4, there is limited support for the G.722 codec. As more and
more hardware vendors start building support for high-fidelity voice into their VoIP
hardware, you’ll see more support in Asterisk for making better-than PSTN quality
calls.

Video
While most of this book focuses on audio, video is also supported in many ways within
Asterisk. Video support is not complete, however. The problem is not so much one of
functionality as it is one of bandwidth and processing power. More significantly, it is
not yet important enough to the community to merit the attention it needs.

* Allison Smith is The Voice of Asterisk; it is her voice in all of the system prompts. To have Allison produce
your own prompt, simply visit http://thevoice.digium.com.

328 | Chapter 15: Asterisk: The Future of Telephony