Re: [ecasound] Re: Resampling in realtime

On Mon, 24 Jan 2005, Simon Werner wrote:

> Maybe I'm do not understand ALSA and how it interoperates with the Delta
> 1010 properly. I have a couple of basic questions about everything works
> under the hood:
> ecasound -t:3 -f:24,8,44100 -erc:5,1 -o rec1.wav

Ok there's probably a typo there, you need to specify an input,
for example '-i alsa,default'.

> Does this set the sampling rate of the Delta 1010 to 44100 Hz and lets
> the Delta 1010 do all the down-sampling?
> Or does it open the Delta 1010 at it's default sampling rate (96 kHz)
> and then save the audio at 44100 Hz (using some kind of a budget

The normal case is that no resampling happens (most soundcards natively
support common srates). If you use the alsa-lib plugin layer (for example
the 'default' soundcard usually goes through the plugin system), alsa-lib
will try to resample the audio (this is currently not very high quality
due to limitations of alsa-lib's resampler) in the case the rate requested
by ecasound is not supported by the hardware.

Ecasound never implicitly resamples anything. You need to use the
'resample' and 'resample-hq' audio objects if you want ecasound to
perform resampling.

If you want to be sure that alsa-lib does not resample anything, use
direct hw-access (for example '-i alsa,hw:0').

--
 http://www.eca.cx
 Audio software for Linux!
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