Here's another child reference:
http://www.freesound.org/people/uberhuberman/sounds/25721/
44.1khz, 16bit audio sample of a 4 year old girl under a Creative Commons
License. Might make for an interesting test - the girl repeats the same words
three times with different voice inflection and energy.
Anthony
--- On Wed, 8/2/12, Rick van Rein <[email protected]> wrote:
From: Rick van Rein <[email protected]>
Subject: Re: [Freetel-codec2] Wideband Codec2 (sneak preview)
To: [email protected]
Date: Wednesday, 8 February, 2012, 2:36 AM
Hello David,
> Encoding more harmonics takes no extra bits. We simply take the pitch
> frequency, and space out as many harmonics as fit in 4 kHz. The
> amplitude of each harmonic is then set by the LPC spectral envelope.
You seem to be confirming the assumptions in my work. I like that ;-)
> So for a few hundred bit/s more we could probably get a Codec 2 running
> at a 16 kHz sample rate: i.e. an "AM broadcast" audio bandwidth of
> between 50 and 7000 Hz. It wouldn't sound as good as an audio codec
> like Opus (or wideband Speex). But booming bass out of a Ham radio
> might be an interesting.
What is your idea about the 12.8 kHz that I am working on? This was
chosen to exploit the FFT to its fullest, given the current packet
frequency. (With 16 kHz your could also achieve that at one packet per
20 ms, of course.)
I'll admit having a hidden agenda on power-of-two-FFT -- I am trying to
exploit the fact the Codec2 reuses 3/4 of the samples in each run of the
FFT. I've documented the _premature_ ideas here:
http://0cpm.org/codec2/speedup/#future-speedup-quarterback-fft
> I am not sure what's required to make very high pitched voices (such as
> children) more intelligible through codecs. Having said that I know my
> 6 year old can be hard to understand through a mobile.
I would love to compare narrow/wideband on such a voice. Could I have a
small sample to work on? 64 kHz sample rate gives the fairest comparison,
but 48 kHz and 44.1 kHz should work well enough. Let me know if you don't
want me to use it in public demo's though.
Cheers,
-Rick
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