[Speex-dev] Delays estimation in Speex algorithms

[Jean-Marc Valin]

Quoting John Ridges <jridges at masque.com>:

> Speex tells me that the decoder is always 5 ms, but it says that the
> encoder is 5 ms for NB, 8.9375 ms for WB, and 10.90625 ms for UWB. Is
> there an extra frame of delay in the encoder that isn't otherwise
> accounted for?

Oh, delay = frame_size + lookahead

If you have a frame size of 20 ms, then there's no choice but to have 20 ms
delay (you can't transmit the first sample until you've received the last).
However, if you have many algorithms that work on the same frame size, you only
pay for that delay once.

    Jean-Marc

> John Ridges
>
> Jean-Marc Valin wrote:
> > Quoting John Ridges <jridges at masque.com>:
> >
> >> I also need to know the precise delays from Speex but I used the
> >> SPEEX_GET_LOOKAHEAD control requests to determine them (plus the
> >> "speex_resampler_get_output_latency" function from the resampler). The
> >> returned values from the Speex lookahead request don't seem to match
> >> with the values you gave Alexander. Am I doing this wrong? Thanks,
> >>
> >
> > What's the difference between what I wrote and what you get from Speex?
> >
> >    Jean-Marc
> >
> >
> >> John Ridges
> >>
> >>
> >> speex-dev-request at xiph.org wrote:
> >>
> >>> Alexander Chemeris a ?crit :
> >>>
> >>>
> >>>> I want to do a careful measure of mic-to-net and net-to-spkr delays
> >>>> in sip media engine and to make it really precise I need to know
> >>>> delays, introduced by Speex algorithms. In particular, I'm interested
> >>>> in delays of:
> >>>> 1) encoder in NB, WB and UWB modes,
> >>>>
> >>>>
> >>> NB: 25 ms, WB: ~28 ms, UWB: ~30 ms
> >>>
> >>>
> >>>
> >>>> 2) decoder (I guess it should be 0?)
> >>>>
> >>>>
> >>> 5 ms
> >>>
> >>>
> >>>
> >>>> 3) resampler. I think it varies depending on input rate to output rate
> >>>> ratio. Any generic formula or at least values for specific ratios
> >>>>
> >> available?
> >>
> >>> The higher the quality, the higher the delay
> >>>
> >>>
> >>>
> >>>> 4) AEC
> >>>>
> >>>>
> >>> 0 ms
> >>>
> >>>
> >>>
> >>>> 5) preprocessor
> >>>>
> >>>>
> >>> 1 frame extra delay (i.e. you get back the last frame you sent the last
> >>> time)
> >>>
> >>> 	Jean-Marc
> >>>
> >>>
> >>> ------------------------------
> >>>
> >>>
> >>>
> >>>
> >>
> >>
> >
> >
> >
> >
> >
>
>
>