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Hi, I'm trying to set up a call monitoring system for work (I work for a non-profit, we're broke so a commercial solution is out of the question) We have ...
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  1. #1
    Just Joined! otkaz's Avatar
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    recording from two audio sources simultaneously


    Hi, I'm trying to set up a call monitoring system for work (I work for a non-profit, we're broke so a commercial solution is out of the question) We have two phone lines, so I built two wiretaps with built in amps. I hooked one of them to the mic input on my ubuntu server. I wrote a script that uses rec from sox with a silence filter. It works perfect for that one line. Problem I'm having is I cant figure out how to record from my second tap. In alsamixer I can only set one recording device even after I installed a second sound card. I was originally trying all this with pulseaudio, but was unable to get any of it to work until I removed pulseaudio. Only way I can think to get this to work is to plug both of the taps into linein and have each of them record on one of the stereo channels, but this is not preferable. I would like to be able to record each phone call on either line into its own separate file even if both lines are in use at the same time. It would be very nice if I could do this all on one computer (as again were broke and don't have spare computers laying around). Another thing I would like, but this part isn't as important right now. If my script is running and I try to use "ssh [host] dd if=/dev/dsp | dd of=/dev/dsp" to listen in live it tells me the hardware source is in use. Anyone have any ideas or directions they could point me? And also yes I do understand my local laws regarding recording phone conversations, and I am in compliance.

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    Linux Guru Rubberman's Avatar
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    Good question. Don't know the answer to that, but my brother-in-law is a recording engineer. He prefers Macs for his work, but he has a fair amount of Linux experience as well. If he knows, I'll pass the info back to you.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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    Just Joined! otkaz's Avatar
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    Quote Originally Posted by Rubberman View Post
    Good question. Don't know the answer to that, but my brother-in-law is a recording engineer. He prefers Macs for his work, but he has a fair amount of Linux experience as well. If he knows, I'll pass the info back to you.
    I would really appreciate that. This is the 3rd linux forum I've posted this question in and have spent a ton of time googling for an answer to this to no avail. You would think that with 2 sound cards alsamixer would let you set two capture devices, but it doesn't or at least I can't figure out how to.

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    Linux Guru Rubberman's Avatar
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    I sent him the message just now. I'll let you know what he says as soon as he responds.

    Sorry I didn't send it to him sooner, but I've been busy this week, and today's my b'day...
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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    Linux Guru Rubberman's Avatar
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    Ok. Here is what my brother-in-law sent back:
    well, there are several unanswered questions there.
    how many audio sources
    what quality (bit depth and sample rate)
    general hardware budget

    I see in the list of ALSA project, both RME and Digigram listed as supported, both of these vendors make a variety of multi I/O cards

    Also M-audio, same as well as Echo Digital Audio. these come in USB and Firewire connection as well

    There are a (small) number of linux audio workstions around so there are probably others as well. Hopefully this answers your question.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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    wonder if this would work?

    What if you assign different interupts to each of the two cards- if they arent already like that.
    Then, run two instances of software via script which initializes each setup individually so that each instance believes it is the only instance running?

    something like

    initialize card1
    load software
    named profile 1
    end

    Initialize car2
    load software
    named profile2
    end

    To the computer, the device is just a device- it doesnt care if its audio or com port. But if the cards are the same then you would find it hard to load the driver and access it from two different programs. So, by using say a sound blaster irq9 and a ac'97 comliant onboard or off at irq10 you would get two different drivers to work with.

    Hope this helps, and forgive me if I undestimate your pc knowledge...

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