[CentOS] Re: recording sound: how 2 control recording level?

Sat Apr 28 17:20:30 UTC 2007
Scott Silva <ssilva at sgvwater.com>

fredex spake the following on 4/28/2007 9:01 AM:
> On Sat, Apr 28, 2007 at 08:40:56AM -0400, Tim Wunder wrote:
>> On Saturday 28 April 2007 6:58:47 am fredex wrote:
>>> Hi gang!
>>>
>>> I'm trying to record (to .wav files) sound coming in on the line input
>>> of my sound card (in this case, output of a tape deck).
>>>
>>> For LISTENING purposes, I can control the level with the Gnome Mixer.
>>>
>>> However, the RECORDING level is not affected by the mixer. As a result,
>>> the recorded audio is badly clipped and horribly distorted.
>>>
>>> I don't understand enough about how this stuff works to have a clue
>>> how to troubleshoot this problem.
>>>
>>> Can someone offer helpful advice?
>>>
>> Dunno about the gnome mixer, but kmix has input and output settings. What are 
>> you using to make the recording? Audacity seems to have a slider for input 
>> volume. 
> 
> I've tried Audacity and rec (from the sox package) and ecasound and 2
> or 3 other things I've run into while Googling.
> 
> I have to admit that yes, Audacity does have a record level slider. And
> it is the single app I've tried in which I CAN control the record level.
> But even then, the recorded sound is slightly clipped sounding (though much
> less bad) when played back. 
> 
> Note that the sound straight from the tape deck, when fed into the computer
> and played through the speakers attached to the sound card, is fine (or as
> close to fine as one can tell given the cheap speakers I have at the moment),
> but when recorded then played back, even the recording from Audacity is
> notably degraded.
> 
> Recording with Audacity seems sluggish--it updates the display (the waveform
> display) in clumps rather than smoothly. When played back, in addition to 
> the muddiness/distortion, there are occasional little defects where it sounds
> as if some samples were lost. I'm guessing that all the graphical stuff
> going on is making the system sufficiently busy that it loses blobs of
> data during recording, which is why I was trying non-GUI recording tools.
> All of them seem to want to record only with the record volume turned all
> the way up. Viewing any of those recordings in Audacity shows that ALL the
> sound is clipped, not just little bits of it, as with Audacity's recordings.
Maybe it is your soundcard. Not all soundcards work 100% with linux. and I
think you would have to have DMA working with it to get good recordings.
Playing directly and recording to storage take different amounts of processor
time. Also, are you recording to a line in port on the card or a mic port.
Line in and mic ports have different attenuation and might need a matching
transformer or some other sort of level control. That is why higher end cards
have both a mic and line in port.

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