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Re: [Discuss-gnuradio] mic audio input

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] mic audio input
Date: Mon, 14 Feb 2005 13:21:19 -0800
User-agent: Mutt/1.5.6i

On Mon, Feb 14, 2005 at 08:19:38PM +0100, Thomas Traber wrote:
> > Gnurus:
> I am not adressed, but answering anyway.
> > Does audio mic input work with audio.source() ?
> Yes, it seems so.

Works for me.  

I have heard of a situation where the alsa library lies about what the
card can do, and then when we request, for example, a single channel,
it fails with "set_channels failed" even though we're requesting a
value that the library says is valid.  The card in question was a SB
Live card.

> When using "from gnuradio import audio" 
> gnuradio tries to load alsa driver. 
> With alsa driver I
> can not change sampling rate. Got the
> following message:
> -----------------------------------
> audio_alsa_source[hw:0,0]: unable to
> support sampling rate 24000
>   card requested 48000 instead.
> -----------------------------------
> Therefore I use:
> " from gnuradio import audio_oss as
> audio"
> The oss driver allows to change sampling
> rate.
> Thomas

When using hw:0,0 as the pcm device the rates GNU Radio can set are
limited to what the card natively provides.  Some cards (including the
Creative Labs Audigy LS I've got) will only do 48000.  If you use
plughw:0,0 the ALSA infrastructure will plug in a sample rate
converter for you.

FWIW, if you compile audio_alsa_{sink,source}.cc with CHATTY_DEBUG set
to true, it will dump all kinds of moderately interesting information
about your card -- including supported data rates and sample sizes.


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