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Date: Wed, 03 Dec 1997 01:33:16 -0800
From: Tristan Savatier <tristan@mpegtv.com>
Organization: MpegTV, http://www.mpegtv.com
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To: Hannu Savolainen <hannu@opensound.com>
CC: Luigi Rizzo <luigi@labinfo.iet.unipi.it>, race@exchange.lancs.ac.uk,
        multimedia@freebsd.org
Subject: Re: MpegTV Problems
References: <Pine.LNX.3.95.971203104830.852C-100000@janus.opensound.com>
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Hannu Savolainen wrote:
> 
> Hi,
> 
> The info.ptr value returned by OSS is computed from the DMA residue count.
> However the old VoxWare driver for FreeBSD doesn't work in this way.
> Instead it works just on the fragment boundaries.

Do you mean info.ptr == number of bytes currently in the driver's fifo ?
I thought that was info.bytes ?

In any case, I have had bad experiences with GETOPTR too. There are
many versions of the OSS driver, and it is extremely hard to know
what IOCTL works in what version.  It seems that neither
GETOSPACE nor GETOPTR worked in old versions, as you know.

In the next version, there will be a environment variable
to choose between the GETOSPACE method and the GETOPTR
method. 

The problem is that it is hard for me to decide automatically
which method will work better (if any), and whether
it is necessary to set a small fragsize or not (since
in theory, if GETOPTR works as advertised, I should
not have to set a small fragsize if using the GETOPTR
method.

-t