[Openal] RE: Openal Digest, Vol 6, Issue 4

[Boris Tkatch]

1. My program is using enumareation. It finds two devices: Generic Hardware
and Generic Software. The result is the same for both of them - some creaks.

2. If I switch hardware acceleration off completely, using either the
control panel or dxdiag utility, the quality of sound is perfect. Turning on
even a basic acceleration brings creaks back. According to dxdiag my audio
card SigmaTel doesn't support hardware buffering.

3. There is something strange about device enumeration.

 a) const ALCchar* namesOfDevices = alcGetString(NULL,
ALC_DEVICE_SPECIFIER);

    gives me two devices: "Genric Hardware" and "Generic Software"

 b) const ALCchar* defaultDeviceName = alcGetString(NULL,
ALC_DEFAULT_DEVICE_SPECIFIER);

    says that Generic Hardware is a default device

 c) If I then create device and context selecting one of the names

    ALCdevice* device = alcOpenDevice(copyOfDeviceName);
    ALCcontext* context	= alcCreateContext(device, NULL);
    alcMakeContextCurrent(context);

    and ask for particular device name

    const ALCchar* deviceName	= alcGetString(device, ALC_DEVICE_SPECIFIER);

    it gives me "Generic Software" for both devices.


-----Original Message-----
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Sent: Sunday, September 10, 2006 3:01 PM
To: openal at opensource.creative.com
Subject: Openal Digest, Vol 6, Issue 4


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Today's Topics:

   1. Re: noise playing ogg files using OpenAL (Garin Hiebert)


----------------------------------------------------------------------

Message: 1
Date: Sat, 09 Sep 2006 18:14:18 -0700
From: Garin Hiebert <garinh at cheesetoast.net>
Subject: Re: [Openal] noise playing ogg files using OpenAL
To: Boris Tkatch <BorisTkatch at jvl-ent.com>
Cc: openal at opensource.creative.com
Message-ID: <450366EA.6010903 at cheesetoast.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I'd suggest two steps:

1)  If your program isn't using enumeration, I'd modify it to do so and
see if the results are consistent for multiple output devices.  At
minimum, your system will probably support a "Generic Hardware" and a
"Generic Software" device, which have different mixing code.  If you
have a hardware-accelerated device available, then things are even
better -- you'll have another device which has a _very_ different code path.

If the problem winds up happening for only one device, that's a valuable
hint.

2)  The diagnostic technique I normally use for cases like this is to
isolate a stream of bad output (one OpenAL source, to use OpenAL's
naming conventions), and dump the raw PCM data that is being placed into
the OpenAL buffers (multiple if you are streaming the data) to a file.
Then, bring that data up in Audacity, Cool Edit, or equivalent, and play
it back from there.

Barring a misunderstanding, this should tell you if this is a case of
garbage-in-garbage-out or good-data-in-garbage-out.  If the data in is
bad, then trace backwards, and if the data in is good, then it would be
worth repeating the data-dump process inside a modified version of the
OpenAL library to trace where the problem is occurring.

Garin



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End of Openal Digest, Vol 6, Issue 4
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