[Openal] Lag playing sounds over the "Generic Software" device
Daniel PEACOCK
dpeacock at creativelabs.com
Fri Sep 5 02:41:10 PDT 2008
Vista will certainly introduce more latency because DirectSound itself sits
on top of WASAPI.
Dan
Creative Labs (UK) Ltd.
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09/05/2008 10:28 "Daniel PEACOCK"
AM <dpeacock at creativelabs.com>
Subject
Re: [Openal] Lag playing sounds
over the "Generic Software" device
Hi Dan and (as always) thanks for your valuable feedback.
I'm using an X-Fi Xtrememusic with the very latest drivers along with
Vista64 SP1 on a quadcore rig. The 250ms estimation is completely
subjetive, but I firmly believe that is clearly more lag than the worst
case of 25+15ms = 40ms you are explaining. I have to try on an XP machine
to discard the problem being related with Vista, but right now I don't have
access to a XP machine with the necessary tools to run the same test. Do
you think this could be related to the new audio layer of Vista?
On Fri, Sep 5, 2008 at 11:18 AM, Daniel PEACOCK <dpeacock at creativelabs.com>
wrote:
Hi Sergio,
A native X-Fi device will certainly give the best (lowest) latency when
starting to play a sound (and updating parameters). The "Generic
Software" device will have additional latency (all software mixers will).
The amount of latency will depend on the soundcard (and how accurate the
DirectSound play and write cursors are updated) plus the fact that
updates are done in a timer callback that is called every 25ms (40Hz).
So, starting to play a sound will have a random amount of latency between
0 and 25ms (depending upon when the 'play' call arrives compared to the
25ms timer) plus a small amount of latency used to write ahead of the
DirectSound write cursor (about 15ms) plus what ever latency is
introduced by the soundcard - i.e. time taken to hear what is written in
front of the write cursor.
250ms is higher than expected though. What soundcard do you have?
A few games have chosen to provide an OpenAL output path in addition to
their own software mixer. This can happen when the game already has their
own solution but wants to give users with high-end soundcards a better
sound experience (e.g high quality 3D audio and EAX effects). Other games
have used OpenAL everywhere.
Dan
Creative Labs (UK) Ltd.
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[Openal] Lag playing
sounds over the
"Generic Software"
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Hi,
I've been using OpenAL for a while in and I've found a different
behaviour between accelerated HW devices and the Generic Software
implementation (on top of DirectSound, I suppose).
The problem is that when using with an X-Fi, the sound plays without no
lag: when you call AL_PLAY over a source the sound starts playing
inmediately. But in the same machine, initializing the OpenAL library in
software mode (opening the "Generic Software" device enumerated by the
library) the sounds starts playing with a noticeable lag (I can't measure
it, but I think that about 1/4 second or so).
I have no EAX effect active and the only difference between the two
executions of the program is the opened device: "Default device" -over an
X-Fi- and Generic Software -over the same card-). Is this normal? Could
it be fixed with some code?
BTW, I'm asking myself... for the AAA games that use OpenAL, do you think
they use the library for every soundcard, or these games implement two
audio paths: one over OpenAL for HW accelerated devices (like Audigy and
X-Fi) and other path for SW devices implemented directly over DirectSound
or other audio software library? For example, in Doom3 and Quake IV (if I
remember correctly) the checkbox for activating the OpenAL renderer is
disabled if you don't have an Audigy or X-Fi.
Any help is welcome._______________________________________________
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Sergio Rodríguez García
sergiorg at gmail.com
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