Re: user soundmodem problems on Inspiron 8200 i810 chipset...

From: Tomi Manninen (isgpini@tl.krakow.pl)
Date: Thu Mar 11 2004 - 11:30:03 EET

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    On Thu, 2004-03-11 at 01:41, tus@voyage.fr wrote:

    > So, if someone tells me how to modify the period and buffer sizes in
    > soundmodem, I'll experiment and see if I can make the problem go away.

    It's the ioctl(SNDCTL_DSP_SETFRAGMENT) call in soundcard/audioio.c.
    This is from the OSS Programmers Guide (pp. 97-98):

      int arg = 0xMMMMSSSS;
      ioctl(audio_fd, SNDCTL_DSP_SETFRAGMENT, &arg);

      The argument to this call is an integer encoded as 0xMMMMSSSS
      (in hex). The 16 least significant bits determine the fragment
      size. The size is 2^SSSS. For example SSSS=0008 gives fragment
      size of 256 bytes (2^8). The minimum is 16 bytes (SSSS=4) and
      the maximum is total_buffer_size/2. Some devices or processor
      architectures may require larger fragments - in this case the
      requested fragment size is automatically increased.

      ...

      The 16 most significant bits (MMMM) determine the maximum number
      of fragments. By default, the driver computes this based on
      available buffer space. The minimum value is 2 and the maximum
      depends on the total buffer space available for the device. Set
      MMMM=0x7fff if you don't want to limit the number of fragments.

    I don't think changing the fragment size is a solution though as it
    affects the real-time preformance of soundmodem... 

    -- 
Tomi Manninen / OH2BNS / KP20ME04

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