Re: [linux-audio-user] sounblaster live platinum and full-duplex recording (noisy)

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Subject: Re: [linux-audio-user] sounblaster live platinum and full-duplex recording (noisy)
From: Erik Steffl (steffl_AT_bigfoot.com)
Date: Mon Aug 16 2004 - 09:09:46 EEST


Lee Revell wrote:
> On Fri, 2004-08-13 at 23:30, Erik Steffl wrote:
>
>> recording seems to be working OK but:
>>
>> in audacity when I record the track it sounds OK
>>
>> however if I generate click track and record then (the click track is
>>playing while I am recording) the recording is really bad (noisy, low
>>quality).
>>
>> I vaguely remember something about full-duplex on sounblaster not
>>being very good, i.e. there's something wrong when using it but don't
>>remember what (bitrate being forced to be very low or something along
>>those lines).
>>
>> However I can't find any information on that subject now (I tried
>>google and creative site), does anybody know details and/or have some
>>pointers to relevant docs?
>>
>> system: debian unstable, 2.6.5 kenrel (with alsa), sounblaster live
>>platinum (with live drive).
>>
>
>
> The hw:x,0 capture device on the sb live is not very good. For good
> results you have to use the hw:x,0 playback device and the hw:x,2
> capture device. You have to use 48khz.
>
> To record at the lowest latencies you have to record more than 2
> channels. This is because the capture buffer size is fixed in bytes;
> doubling the number of channels halves the amount of time between
> interrupts with a fixed buffer size.
>
> This did not work at all until very recently, I believe you need the
> ALSA 1.0.6-rc1 release candidate.
>
> Search the recent alsa-devel archives for 'emu10k1 low latency capture'
> and 'emu10k1 multichannel' for more info.

   thanks for the info, now I have to figure out how to use it:-) it
looks like audacity uses oss (/dev/dsp) so I guess I could configure
alsa so that /dev/dsp is hw:x,0 and e.g. /dev/dsp1 is hw:x,2

   right now I'm not even at the point of caring for latency, for some
reason the recording is of really bad quality when I use full-duplex
(i.e. playback of click track and record), the quality is OK if I only
record.

        erik


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