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Re: [linuxham] Trying fldigi 2.04 install

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  • Rick Kunath
    ... It s a supported sample rate issue. Up and down converting for cards that have drivers not properly supporting requested sample rates (or actual hardware
    Message 1 of 43 , Dec 3, 2007
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      Rick wrote:

      > This is EXACTLY what I am experiencing. Also, does it with most other
      > programs.

      It's a supported sample rate issue. Up and down converting for cards
      that have drivers not properly supporting requested sample rates (or
      actual hardware not supporting sample rates) can cause this.

      The Intel HD is one that acts this way.

      It does not support (at least in Linux) any sample rate under 44,100.

      At a forced sample rate of 44,100, or 48,000 where I set my test box
      using the FLdigi setup options on alpha 2.05c, and under Portaudio,
      there are no clicks.

      OSS Free (or alsa-oss emulation) does exhibit the clicks as the card
      and> Hi Tim,
      > the alsa upconverting apparently does not work correctly with this
      Intel HD driver. It's likely an Inter driver issue.

      So the 2.05 release (using the Portaudio API) will likely fix some of
      these issues for folks with cards that don't directly support all of the
      sample rates that they should.

      This is an example of why you need to see what sample rates the
      soundcard driver supports under Linux for any card you are thinking
      about using. Some of the ALSA sample rate conversions work well, some
      drivers are lousy. Better to have a card that properly supports all of
      the rates you'll need, then no conversion is necessary.

      The 2.05 release won't fix other apps that still use alsa-oss emulation
      on these cards.

      I don't use the Intel HD audio chipset for radio applications, having
      Audigy4 cards installed on the devel workstations I do radio on and the
      Intel HD soundcard chipset disabled in BIOS.

      Rick Kunath, k9ao
    • Rick Kunath
      Hi Tim, ... Portaudio is a cross platform API. It sits between your application and the underlying sound system, in most cases folks are using ALSA. In your
      Message 43 of 43 , Dec 7, 2007
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        Hi Tim,

        Tim Gimmel wrote:
        > Rick,
        > The new portaudio stuff in Fldigi 2.05 fixed my problem with the
        > "ticking" sound. Can you tell me how it (portaudio) works, or give me
        > some hints that I can give to the alsa folks? WSJT 6 uses portaudio
        > also and would love to be able to make it work correctly. I have to
        > admit I have been working with Linux for over 10 years and I still just
        > don't understand the audio system. If you know of a site that has a
        > good explanation of Linux audio from oss to alsa to portaudio I would
        > love to read it!

        Portaudio is a cross platform API. It sits between your application and
        the underlying sound system, in most cases folks are using ALSA.

        In your case, you were able to use Portaudio and the FLdigi code to
        force a supported sample rate that your Intel HD sound card could handle
        natively. This is 44,100, 48,000. The card won't support lower sample
        rates, but digital apps want to use them, like 8000, 11,025, etc. There
        are a variety of standard sample rates for sound cards, yours does not
        support all of these (at least in Linux and ALSA.) And that's why the
        ticking. ALSA had to up convert, and the Intel HD driver for ALSA is not
        up to the task right now.

        Portaudio and a forced (in FLDIGI) supported sample rate fixed the
        ticking because no conversion was then needed on the sound stream.

        If WSJT can select a sample rate, you should be able to take care of the
        problem easily. You might want to ask Joe to put that in the code.

        Rick Kunath, k9ao
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