[Speex-dev] Delays estimation in Speex algorithms

Alexander Chemeris Alexander.Chemeris at sipez.com
Wed Jul 1 09:02:03 PDT 2009

Thank you for clarification. I attached a patch which (IMHO)
makes it more clear for everyone who just read Doxygen
docs. Resampler latency docs wording was just ambiguous
IMO, so I made it more robust to fast reading.

On Wed, Jul 1, 2009 at 5:16 PM, Jean-Marc
Valin<jean-marc.valin at usherbrooke.ca> wrote:
> Alexander Chemeris a écrit :
>> On Tue, Jun 30, 2009 at 4:38 AM, Jean-Marc
>> Valin<jean-marc.valin at usherbrooke.ca> wrote:
>>> Alexander Chemeris a écrit :
>>>> 2) decoder (I guess it should be 0?)
>>> 5 ms
>> Hum, interesting. So, e.g. for NB mode delay is
>> 20 (packet size) + 5 (encoder lookahead) + 5 (decoder delay) = 30, right?
> Correct
>>>> 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
>> Seems we need to update our Speex sources. Our version has no
>> speex_resampler_get_[out|in]put_latency() functions. Should I
>> sum values of input and output latency to get overall latency?
>> Actually, why do you separate input and output latency? For
>> a user, resampler is a black-box, which logically has a single
>> latency value. Two latencies are confusing.
> You don't sum them, you just get the latency in different units.
> speex_resampler_get_input_latency() will return the latency in input
> samples, while the other will give you the same value, but expressed as
> a number of output samples.
>        Jean-Marc

Alexander Chemeris.

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