[Speex-dev] Speex Resampler quality

Premkiran Mannava loverays at gmail.com
Mon Feb 18 08:08:02 PST 2008

Thanks for your inputs.

I quickly tested manually using my golden ears and I find the quality of
perception is perfect :)  Though I get a very bad PEAQ test value a manual
test seems to be better.

But I am also looking for any kind of objective measurement to validate my
test appl.  Is it not possible to objectively validate Speex resampler using
any kind of code or tool (may not be a PEAQ based tool)?

I have few more questions....

1.  Is it required for speex resampler input buffer length to be multiple of
SpeexResamplerState's frac_advance value?  I find if above is not the case,
samples are missing in fractional rate conversion.
2. Out of resampler_basic_direct_single and
resampler_basic_interpolation_single, which of them is nore reliable one?
Can I use resampler_basic_direct_single for all purposes as this seems to be
simpler implementation.  Which one would you recommend for?

On Feb 18, 2008 8:54 PM, Keith Kyzivat <kkyzivat at sipez.com> wrote:

> On 2/18/08, Premkiran Mannava <loverays at gmail.com> wrote:
> >
> > Hi,
> >
> > *"That's in general not very reliable. You can get PEAQ to say all sorts
> > of silly things."
> >
> > Can you provide me links for any more effective tools other than PEAQ?
> > Which is more reliable for Speex resampler?*
> I can already tell you what Jean-Marc will say -- use your ears :)
> Manual testing is the best way to go for doing actual quality determining.
> To prevent regressions though, a tool like PEAQ might be useful -- not so
> much the actual quality level it determines, but the value changing a lot
> could then get you to do another manual test.
> *"strongly suspect that it's just not compensating for the delay
> > introduced by the resampler. Because higher quality means higher delay,
> > you'd find that PEAQ doesn't like it when you increase the resampler
> > quality. You can easily remove the delay (well, not remove it but skip
> > the zeros it produces) by calling speex_resampler_skip_zeros() once,
> > before you start the processing."
> > *
> > *When I use speex_resampler_skip_zeros() for 44100 to 48000 conversion,
> > I got a very bad quality value when I used PEAQ.  Do you suggest me not to
> > use this function for fractional rate conversions?*
> Doesn't this tell you that PEAQ doesn't work well with speex?
> --
> Keith Kyzivat
> SIPez LLC.
> SIP VoIP, IM and Presence Consulting
> http://www.SIPez.com
> tel: +1 (617) 273-4000

" Excellence is not an act....but a habit..."
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