[GnomeMeeting-list] Re: audio - fragment size mismatch

[Christian Lambert <clambert sgi com>]

Hi,

I investigated more on this issue with the 4front OSS folks, and
they found a programming error for OSS in the pwlib oss.cxx module:
 
The Envy24 card uses fixed fragment size so applications cannot change it.
This may cause problems with applications that try to do something stupid.

The message about "fragment size mismatch" is related with this. However
the main reason is that the application doesn't make certain ioctl() calls
in right order. As documented in our Programmer's Guide the application
should set the number of channels, # of bits and sampling rate before
calling SNDCTL_DSP_GETBLKSIZE or SNDCTL_DSP_GET[IO]SPACE.

The application has two errors (at least):

1) It must in not call SNDCTL_DSP_RESET after opening the device.

2) It calls SNDCTL_DSP_GETOSPACE and SNDCTL_DSP_GETISPACE before setting
the sampling parameters.

Best regards,

Hannu
-----
Hannu Savolainen (hannu opensound com)
http://www.opensound.com (Open Sound System (OSS))
http://www.compusonic.fi (Finnish OSS pages)


On Wed, 19 Jun 2002, Christian Lambert wrote:

| 
| I use gnomemeeting 0.92.1 with the latest libs from mandrake cooker
| RPMS packages.    I'm using Mandrake 8.2.
| 
| I can't get the sound to work on my Envy24 (audiophile 24/96) using
| OSS commercial drivers.   When it tries to output audio, there is
| only garbage coming out on the external DAC I use thru SDPIF and it can't
| get a lock on a frequency.  Normally it works fine even for 8Khz.
| 
| I do get an error message in syslog that says the application is trying
| to do a DMA of 1k which is too small for the hardware.  It needs a minimum
| of 2k to work from what I understand.  This is not your typical soundcard tough,
| it's in the category of pro soundcards used for digital recording and playback.
| 
| It also does not have an OSS mixer, it's got channels for input/output
| and you need to use a mic pre-amp for the line-in.  But I'm planning on getting
| the input from the usbaudio microphone and outputting thru the envy24 dsp0, so
| I'm only interesting in getting the sound output to work, not recording.
| 
| I looked quickly at the pwlib file called oss.cxx, but I didn't find in it
| that it forced a size of 1024, so I'm a bit confused.
| 
| Does anyone know which change I would need to make in order to make it
| work with this soundcard?
| 
| Jun 17 22:14:16 onyx4 kernel: Envy24: Fragment size mismatch: hw=2048, sw=1024
| Jun 17 22:14:16 onyx4 kernel: Envy24: Application bug detected. Fix ioctl()
| calling order
| 
| Let me know
| 
| 

-- 
Christian Lambert               Networking & Communications
clambert csd sgi com            Global Product Support
Mountain View, CA               SGI