PC capture of digital audio?

Discussion in 'Playback Devices' started by Will.MA, Jan 23, 2006.

  1. Will.MA

    Will.MA Stunt Coordinator

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    I have a NForce-2 based board [DFI Lanparty NF II Ultra B] with SPDIF coax inputs/outputs on board. I would like to capture audio programming from a HD-compatible cable TV box using a digital coax line to connect the devices via SPDIF.

    The problem is that I don't hear any programming through my PC. The audio program that I use to record audio onto my HDD, Digitope Media Digitizer, doesn't detect any sound info, nor does it record any once the recording is started. I have double-checked that the mute function of the SPDIF input is off in WXP. I am sure that I have a SPDIF input on my board and that the program source is properly connected to the appropriate input jack. If I connect the coax from HDTV box to my digital receiver, I hear audio.

    Is there something that I'm missing? Perhaps a step that I'm not aware of? Any help or insight would be greatly appreciated.
     
  2. ChristopherDAC

    ChristopherDAC Producer

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    Is this a full-duplex card, or no?

    I ask because my audio card is not. If I want to record from the SPDIF input, I have to put it into "Digital In" mode in its device control panel, at which point system sound is disabled and the SPDIF out does nothing but loop through the input. If I try to play a sound file, it "detects an error trying to open the wave output device".
     
  3. Will.MA

    Will.MA Stunt Coordinator

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    Thanks for taking a crack at the problem C-DAC.

    I don't have a outboard sound "card." It has on-board AC3 encoding/decoding. Here are some details about the main board's audio capabilities that I took from the DFI website:

    -AC'97 2.2 S/PDIF extension compliant codec

    -Supports Microsoft® DirectSound/DirectSound 3D

    -AC’97 supported with full duplex, independent sample rate converter for audio recording and playback

    -6 channel audio output

    I think that if it was half-duplex, I would get bouncing program levels on the media recorder's level meters to indicate that sound is indeed being recorded. Therefore it seems the problem must be due to something else.
     
  4. ChristopherDAC

    ChristopherDAC Producer

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    Motherboard sound, eh? OK, I missed that.
    With a half-duplex setup, either the digital input or the system sound output [analog or digital] can be active at one time. If I don't have digital input selected, and I open my sound recorder [NERO Wave Editor in this case], the recording level meters stay bottomed-out unless there is audio present at the analog inputs (or whatever other input source I have selected -- I have a choice of several). It's only when I have digital input selected -- which incurs a popup box telling me that normal audio functions are now disabled -- that the digital input has the power to choose the level meters.

    On the other hand, reading the specifications, it occurs to me that -- just perhaps -- your media software is not prepared to accept the AC-3 stream. You can test this by setting the output audio format of your cable box to "PCM" rather than "Native", I expect.
    If that turns out to be the case, all is not lost. I don't actually know of any sound-recorder programme which recognises an AC-3 stream, but I do know that it's possible to set up an open-source media player programme, VLC Media Player, to record just about any concievable media stream. If you want details, I can furnish them.
     

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