Re: Sample rate conversion of audio input device
Re: Sample rate conversion of audio input device
- Subject: Re: Sample rate conversion of audio input device
- From: Christof Faller <email@hidden>
- Date: Tue, 30 Jul 2002 20:19:14 -0400
>
2
>
>
For the echo cancellation timing is important. Can I obtain any
>
knowledge about the delay introduced by the SRC when using
>
AudioConverterFillBuffer or AudioConverterConvertBuffer?
>
>
>
The converters work in real time.
>
But still I would expect that the down-samplers/up-samplers introduce
delay (because of the causal low-pass filters which are used). In other
words, if for example I downsample 44.1 => 16 and upsample again 16 =>
44.1 I expect that the resulting data is delayed compared to the original.
For most applications this delay is negledable. But for acoustic echo
cancellation it is important to know the delay exactly. Once I get to
the point of inserting my echo canceller I will write a routine which
figures out this delay (e.g. convert a pulse and see where the maximum
is after the various processing steps).
But generally, for applications such as tele-conferencing it would be
useful to be able get get this number from the API.
Also, it may be that because of this effect the time-stamp given by
AudioUnits (when used with SRC) is not sample accurate.
Chris
_______________________________________________
coreaudio-api mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/coreaudio-api
Do not post admin requests to the list. They will be ignored.