Sevana Oy » codec

AQuA – Audio Quality Analyzer is now available for 64 bit servers!

admin — Mon, 15 Jun 2009 17:34:10 +0000

Hi,

Great news! Now AQuA (Sevana Audio QualityAnalyzer) is available under 32bit and 64bit operating systems!

- test voice and audio files quality

- compare two audio and voice files

- test voice codecs’ quality

- perform voice and audio quality measurement

Now this functionality is available both for Windows and Linux 64 bit and 32 bit systems. Voice quality testing software for Linux servers is provided on request.

How can I test this voice quality measurement software?

admin — Mon, 30 Mar 2009 19:09:20 +0000

Sorry for the pause with our new posts on voice quality! This temporary information gap will be over soon and meanwhile we would like to give an answer to such questions as:

- how can I compare two audio files to test voice quality?

- how can I test my codec for voice quality it provides?

The answer to the questions about is: please use contact information on these matters from here: http://www.sevana.fi/about.php

- is there a demo version I can play with?

Yes, it’s available for download from here: http://www.sevana.fi/audio_speech_codecs_quality_analysis.php

- demo version doesn’t allow comparing files! What can I do?

Please use contact information from here: http://www.sevana.fi/about.php and you may get a fully functioning software for your testing purposes!

- are there any updates to the functionality presented in the demo version?

Yes! There is a new version that actually tells you why there is a quality loss providing quantative feedback! And… you know where to go to inquire that version

Stay tuned!

What is that statistical speech model you are talking about?

admin — Thu, 26 Feb 2009 06:35:19 +0000

Language consists of sounds, right?. Every individual generates a unique set of sounds, correct?. However, one can distinguish standard speakers (SS), generating average kinds of sounds, who are subdivided according to their age, gender, region, social status, education, occupation etc. One should determine sound frequencies, probabilities of sounds following each other, intonation contours, vocabularies, physical properties of individual sounds for every standard speaker. That is not easy, but based on these data one can simulate natural speech flow! System, however, should also include statistic information about the population structure and with its help generate speech flows with those features, which characterize population of some region or the whole country. Frankly speaking, statistical model contains statistics data about the population structure, speech based on standard speakers, speech signal processing facilities (algorithms for synthesis), means of sounds parameters speed determination, algorithms for sounds generation and standard speakers distributions. Confused? Sounds tuff? You can read more and inquire an audio file with a speech model right from here (http://www.sevana.fi/audio_speech_codecs_quality_analysis.php). Next time we discuss what is Signals synchronizer and after that we’ll approach the core of this technology and its major know-how – the analytical module! See you tomorrow!

Confused on how to measure voice quality after all? Here is the answer – signal + noise + speech model + analytics = state-of-the-art approach!

admin — Tue, 24 Feb 2009 06:32:31 +0000

Today we would like to propose a yet another concept for voice quality testing and estimation. We believe that a successor for PESQ and other methods should have a generator of test signals that allows sound signal generation according to one of the sound flow models (we explain them in further posts). It can be either a particularized set of sound signals or a signal, received as an output of statistical speech model. Generator’s signal can either be saved for follow-up usage or be exposed to processing and estimation. Bank of signals stores sound data, received as a result of signals’ generator work or from some external sources (you can ask for sample speech models from http://www.sevana.fi). Accordingly, an input of estimation block is a signal of generator directly or one of the bank of signals. Test signal is the input of the synchronizer or of the device under test, which can be for example, a vocoder, compressed/decompressed audio, just an audio/voice file or a communication channel. The output signal of the device under test is an input of synchronizer as well. The synchronizer matches in time initial signal and a processed signal. The synchronized signals in chunks are input into analytical module, which determines the degree of similarity for signals and issues the quality estimation as the measure of similarity between the initial and the processed signals. Misty? The point is that a successful voice quality testing system should have:

- Test signals generator
- Noise signals generator
- Statistical speech model
- Signals syncronizer
- Analytical module

Stay connected and we describe all of these modules in our upcoming blog posts!

Speech Intelligibility is not enough – let’s go for speech transmission index! The truth is out there…

admin — Sat, 21 Feb 2009 12:44:15 +0000

Today we would like to present two more methods to measure voice quality for example degraded by using a lossy codec or transmitting via mobile or fixed networks. These are methods similar in the approach and differ in implementation scheme, here they are:

STI (Speech Transmission Index). We may approximately consider speech signal as broadband signal modulated by low-frequency signal. Articulation speed determines modulation frequency. When modulation depth decreases, speech signal becomes similar to noise and its intelligibility decreases. Accordingly, intelligibility decrease can be estimated according to modulation depth decrease also. Whole speech range is divided into 7octave bands. An octave noise signal is the input. The test signal intensity distribution agrees with the distribution of speech signal intensities. The modulating signal frequencies vary from 0.5 to 12.5 Hz with one-third-octave interval (14 frequencies in all). The STI measuring method is stated in the International standard IEC 268-16.

RATSI/STIPA (Rapid Speech Transmission Index). The STI method needs a lot of measuring procedures and calculations. A simplified method was developed, which provides for measuring only in 2 bands with 5 modulation frequencies and reduces the number of measuring procedures and calculations. For good intelligibility RASTI values must be not less than 0.6.

As these are analogous methods they have common disadvantages: speech transmission index as well as rapid speech transmission index imitates speech production process by means of noise model, but to take into account the properties of speech production and hearing in such a way is far from optimum.

Anticipating why we are posting short methods description and their disadvantages? That will be discovered in the next post about C50 – factor of clearence method.