Hum...
I guess it would be simpler to create a voice captcha to be used in
websites.
The idea is to use the same thing recaptcha uses (human power).
http://www.google.com/recaptcha/intro/
All you will need is a larger number of samples.
The user would need to identify two random words by audio.
If the user dont write the correct words, or just one of them, you give
another two words to the user.
I really think you dont need a huge number of samples, but to be a
functional captcha it is a good idea to block more than x consecutive
errors from same ip, and at the analysis cut below the 'median' of the data.
This is just an idea... maybe you can contact the recaptcha people to see
if it would be possible to use the audio captcha they already have for this
purpose.
Statistically, the distribution of errors will give you all the levels you
need. :)
[]s, Ricardo Mello (gandhi)
2014-11-29 20:00 GMT-02:00 Kristoff <[email protected]>:
> Hi all,
>
>
>
> In theory, it is simply: errors in the communication path result in
> errors in the codec2 stream, that might or might not get corrected by
> the FEC-system. This may result in impaired speech decoding.
>
> The problem is this:
>
> As codec2 supports more and more different bitrates and different modems
> are getting developed using different bitrates, different FEC scemes and
> differt modulation scemes, the end-result -the demodulated voice audio-
> can differ quite a bit depeding on a lot of different factors,
> especially if the transmission-stream is impacted by interference.
> In addition to this, the subjective perception how good / acceptable /
> bad decodec voice sounds will probably differ from person to person.
>
>
> In the end, the proof of the pudding is in the eating. That is why we
> would like to propose this:
>
> - We are looking for somebody who can set up/create a webbased system to
> allow people (anybody on the web) to "score" audio-samples. These
> samples are the same audio-fragment per test-batch, encoded using
> different codecs, different bitrates or
> formated/modulated/corrupted/demodulated/extracted using different modems.
>
> - A test would be a batch of (say) 10 audio-samples. The user should get
> to hear them one by one and be able to give a score (say between 1 and
> <whatever>) for everyone of them.
>
> - For every tests, different audio-samples and/or in different order
> should be provided.
>
> - The user should not receive any "background" information about the
> audio-sample, this to assure the double-blind characteristic of the test.
>
>
>
> The end is to have a database of subjective scores by as much people as
> possive, of codec2 encoded at different bitrates and the resistance of a
> particual modem to transmission-errors
>
> One of the questions we want to answer is:
> "do we need add FEC to a modem to transmit codec2 over the radio"? Does
> it help? Does it help enough to counter the lower S/N due to the wide
> bandwidht.
> Or perhaps a "halfway" sollution and only protecting part of the voice
> data is better?
>
>
>
>
> As noted above, this is something where -I think- the community can do
> its part. If you have experience with setting up web-based application,
> this is your change to win etteral fame in "the codec wars".
>
> This initiative should really will help codec2 by allowing the
> developers of the codec, the modems and the upper-layer applications to
> mix-and-match the correct combination of all element to provide hams
> worldwide the best possible codec2 DV experience, on HF and on VHF/UHF.
>
>
>
> 73
> Kristoff - ON1ARF
>
>
>
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