speech recognition software

What are amplitude, frequency, wavelength?

admin — Sun, 30 Aug 2009 18:50:14 +0000

I think that 16 kHz / 16 bit recordings should be sufficient for the development of a speech model. But what does that mean? A good article explains the differences between amplitude (16 bit recordings are more precise than 8 bit recordings), and frequency, wavelength (the human ear can distinguish up to 20 kHz; you need the double amount of kHz for recording; 16 kHz means that 8 kHz are distinguished - should be sufficient for speech).

Replacing HTK by Sphinx?

admin — Fri, 28 Aug 2009 22:45:07 +0000

You need to install HTK if you want to run simon with the whole functionality. HTK is not included, it has to be downloaded from a different source (registration required). From my point of view, this information could hint people who are familiar with Sphinx and Qt into the right direction:

“simon uses the NON-FREE HTK for that. Only _one_ class in simon comes into contact with the HTK. The model compilation manager. This class: http://speech2text.svn.sourceforge.net/viewvc/speech2text/trunk/simonlib…. Those 1200 lines (including other, julius related stuff) are everything that links simon to the HTK. The class could very, very easily be replaced with one that uses something else.”

simon should continue to make use of HTK because there are things that you never should do:

“They did it by making the single worst strategic mistake that any software company can make:

They decided to rewrite the code from scratch.”

Well, but maybe there is someone out there who would want to start a fork of simon, and replace HTK by Sphinx? Of course, this would be a completely different project.

I think that Sphinx could use a GUI.

Sound frames - a, e, i, o, u, b(e)

admin — Sat, 18 Jul 2009 10:49:11 +0000

Let’s take a look at a few sound frames (click picture to enlarge):

U+0061 (a), U+02D0
The sounds in this article correspond to the German pronunciation.

U+0065 (e), U+02D0

U+0069 (i), U+02D0

U+006F (o), U+02D0

U+0075 (u), U+02D0

First part: U+0062 (b) - second part: U+0065 (e), U+02D0

Julius package for Ubuntu

admin — Thu, 18 Jun 2009 17:49:13 +0000

Soon, there should be an updated Julius package for Ubuntu (4.0.2 -> 4.1.2).

Characteristics of the sound “a”

admin — Wed, 20 May 2009 01:37:45 +0000

Let’s take a look at the characteristics of the sound “a” (spoken like in father). Here is a screenshot of Audacity which shows the repetitive pattern of the sound “a”:

I have marked the different waves with numbers 1, 2, 3, 4, 5. The waves with the same number are slightly different one from another, but they are similar. It is a repetitive pattern. Let’s extract a complete frame of the sound “a”:

The above picture shows the first frame. Let’s compare the first frame with the second frame:

Take a look at the yellow marked area, and compare it with the corresponding area of the previous picture. It is slightly diffent.

This was a short introduction into signal processing. These sound waves can be analysed by software like the HTK toolkit.

Installing simon-juliusd-0.1-alpha2.exe

admin — Sun, 22 Jun 2008 07:19:33 +0000

I just downloaded the obviously recently released program simon-juliusd-0.1-alpha2.exe. Before running the program, I checked it with ClamWin (I always do that before I install new software). It is OK, so I will install this program on my computer. The program is licensed under the GPL. On my computer, the program simon.exe was installed on the location “H:\Program Files\simon\simon-0.1-alpha-2.”

Here is a screenshot:

But now, it is beginning to get complicated. Take a look at the next screenshot:

So to use this program successfully, there are several additional programs needed. I need the HTK toolkit, and Julius. And there are further components necessary. I think I will stop the installation now. Or should I continue? At the moment, I am not sure. I think, that I will hit the next button.

I won’t publish a screenshot from the next step. But it is about HTK programs HDman, HCopy, and several other programs. I think (but I am not sure) that it is necessary to tell Simon the path on which location those programs are installed. A few months ago, I made some first steps with HTK and Julius, but everything was pretty complicated. At the moment, I am reading a few pages in the HTK book, everything is very abstract. And it takes a lot of time to get involved. But it is possible! You just have to stay focused.

VoxForge dictionary isn’t encoded in UTF-8

admin — Sat, 21 Jun 2008 03:24:41 +0000

I just downloaded the VoxForge dictionary (2.6 MB), and opened it with Notepad++. Obviously, it is encoded in ANSI, not in UTF-8. That’s OK because it does contain just standard characters. I am guessing that this dictionary is compatible with ASCII. But I would suggest that future versions should be published in UTF-8.

Switching from Arpabet to IPA

admin — Sat, 21 Jun 2008 00:27:54 +0000

Obviously, the CMU pronouncing dictionary is using the Arpabet. The Arpabet has the advantage that it is possible

“to represent phonemes with ASCII characters.”

But today, the UTF-8 standard is becoming more and more common. In my opinion, there should be a discussion to switch from Arpabet/ASCII to IPA/UTF-8. The IPA is easier to read than the Arpabet. And UTF-8 should be backwards compatible to ASCII (at least, as far as I know).

RFC 4267: VoiceXML, PLS, SSML, SRGS, CCXML

admin — Thu, 19 Jun 2008 04:30:06 +0000

Recently, I read the document RFC 4267. In my opinion, this framework is something very interesting.

learning sphinx automatic speech recognition

admin — Mon, 24 Mar 2008 06:17:44 +0000

You can learn to use the CMU Sphinx automatic speech recognition system. I followed several steps of this tutorial, but I didn’t succeed. I used Ubuntu Linux. What was the problem? Well, there occurred several smaller problems. I could solve a few of them, but not all. I will try again.

2008-04-01: Doubt about sphinx3 installation