Monitoring soundcard line-out level

This is a discussion on Monitoring soundcard line-out level within the C Programming forums, part of the General Programming Boards category; Hello everyone, I'm a hobby programmer, using mostly LCC (a Windows C compiler), and also have C++Builder 5. My question: ...

  1. #1
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    Question Monitoring soundcard line-in or line-out level

    Hello everyone,

    I'm a hobby programmer, using mostly LCC (a Windows C compiler), and also have C++Builder 5.

    My question:

    How can I monitor the actual line-in or line-out signal level on a PC (SoundBlaster) sound card in Windows 9x?

    I don't mean get the volume control settings, but the actual signal level.

    The project:

    I'd like to make a simple gain limiter for use with a TV card (commercials are ridiculously loud). Adjusting volume level is simple enough, I just need a signal reference.

    The TV card plugs into the soundcard externally, so either line-in or line-out monitoring would work.

    Thanks.
    Last edited by moose; 04-10-2009 at 05:31 PM. Reason: forgot something

  2. #2
    ATH0 quzah's Avatar
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    See if your card manufacturer has an SDK you can download.


    Quzah.
    Hope is the first step on the road to disappointment.

  3. #3
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    Thanks, but I've googled myself silly without success.

    All I can find is some really old DOS info, and nothing to monitor line signals.

  4. #4
    Kernel hacker
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    To be able to affect the ACTUAL output level without adjusting the volume control, you need to have access to the raw data prior to it going to the sound-card and analyze it to determine the sound-level. That's far from easy. Once the sound-data has reached the actual sound-card, it's too late to do anything in software.

    --
    Mats
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    Please don't PM me for help - and no, I don't do help over instant messengers.

  5. #5
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    I don't mind adjusting the master volume control (via software), so I don't need to manipulate the raw data output. I just need to access the signal level for a reference.

    I have a freeware app (EchoFilter 2) that does realtime AGC (auto gain control), so I know it can be done. However, that app also does graphs and charts, and the 333MHz computer with the TV card struggles to adjust the volume without lagging.

    Thanks.
    Last edited by moose; 04-10-2009 at 09:04 PM.

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