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Date: Wed, 23 Jul 1997 23:24:32 -0400
From: Randall Hopper <rhh@ct.picker.com>
To: Luigi Rizzo <luigi@labinfo.iet.unipi.it>
Cc: freebsd-multimedia@FreeBSD.ORG
Subject: Re: dma handling in the sound driver
References: <19970723220732.54270@ct.picker.com> <199707240210.EAA25526@labinfo.iet.unipi.it>
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Luigi Rizzo:
 |Knowing which ioctl's are used by apps (commercial and not) would
 |certainly help to prioritize the work on some rather than others. 

Ok.  Well, the only commercial app I have this info for is the MpegTV's
Linux mtv, since I buzzed it out when debugging the no-audio problem
(before dumping it for the FreeBSD version).  Here's the /dev/dsp ioctls it
uses:

   SETUP:  DSP_SETFMT
           PCM_WRITE_CHANNELS
           PCM_WRITE_RATE
           DSP_SETFMT
           DSP_STEREO
           DSP_SETFRAGMENT (requests 127 buffers, each 1024 bytes each)
                           (driver keeps 1024 buffer size, but adjusts 
                            requested number of buffers down to 64 since
                            64k is all the mem that's available)
           ...

   MAIN PLAY LOOP:
           DSP_GETOSPACE   - reflects free space across 64 bufs, each 1024bytes
           write()         - if space

   ON MUTE OR EXIT:
           DSP_RESET


Randall