[Speex-dev] echo cancellation input/output delay

[danflu at uninet.com.br]

Hi,

I've been reading the speex echo cancellation documentation
and it says :

".... It is important that, at any time, any echo that is
present in the input has already been sent to the echo
canceller as echo_frame. ... ";



All I'm doing in the echo cancellation process is
initializing it once with a call to :

SpeexEchoState* speex_echo_state_init(int frame_size, int
filter_length)

and calling  speex_echo_cancellation(m_echoState, rec, play,
out) to remove the far-end echo from the input signal.


So here is my question:

if the first sample in the rec buffer refers to a guiven
time 't' the first sample in the play buffer is supposed to
refer to a guiven time 't - delta' ???

or in other words:

speex_echo_cancellation(m_echoState, rec(t), play(t-delta),
out) is correct ?

If so... how many millisencons this 'delta' is supposed to
be ?

Thanks in advance,
Daniel