[Openal] 40msec Latency???

[Anders Backman]

I was informed that they were running on a Creative Audigy card, so I was
very suprised to hear about the latency.
After I investigated their hardware, it turned out that the computer was
equipped with some on-chip, Audigy simulating soundcard.

After installing a Creative Audigy 2 SZ with hardware drivers the latency
got down to < 1ms,

We also tried a few other hardware options:

SoundBlaster Audigy ADVANCED MB   40ms (onboard-chip)
Creative X-FI Xtrem Audio                      35ms
Creative X-FI Xtrem Music                       8ms
Audigy2        <0.1ms


So with that setup it seemed that the Audigy2 gave us the best performance.

And yes, we are using the hw accelerated drivers for the sound card.
OpenAL++ uses that whenever it finds it available.

/Anders

On 3/29/07, Daniel PEACOCK <dpeacock at creativelabs.com> wrote:
>
> Hi Anders,
>
> >> Creative Audigy SZ
>
> Do you mean Audigy 2 ZS or Audigy SE perhaps ?
>
> Which OpenAL device are you actually using ?
>
> The "Generic Software" device will have the highest average latency
> because it mixes audio in chunks that are prepared every 40ms. This should
> give a worse case scenario of 40ms latency when you call alSourcePlay *just*
> after a chunk of audio has been mixed. The "Generic Hardware" device should
> give better latency, and the Audigy <native> OpenAL device should give the
> lowest latency.
>
> Dan
>
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> [image: Inactive hide details for "Anders Backman" <andersb at cs.umu.se>]"Anders
> Backman" <andersb at cs.umu.se>
>
>
>
>     *"Anders Backman" <andersb at cs.umu.se>*
>             Sent by: openal-bounces at opensource.creative.com
>
>             03/28/2007 12:07 AM
>
>
> To
>
> openal at opensource.creative.com
> cc
>
>
> Subject
>
> [Openal] 40msec Latency???
> Hi all.
>
> Im using windowsXP.
> Creative Audigy SZ
> OpenAL 1.1 (SDK from CVS, runtime from OpenAL installer)
>
> Some guys at a department here at the University did a funky experiment
> where they need to know when a sound is actually played, relative to some
> visual stimuli.
>
> To measure this, they used a system, where they send a signal over the
> serial port at the same time as they start playing a preloaded ready-to-go
> sound-sample using OpenAL (or OpenAL++ really).
> At the other end of the serial port, there is a computer that measures
> (samples) the signal arriving at the speaker as well as receiving the serial
> port signal.
> I
> t turns out that the speaker signal arrives 40msec (exactly) after the
> serial port signal. We have a 1msec wait buffer on the serial port, so its
> really 41msec.
>
> I cant really find out why there should be a 40msec latency between
> issuing a sound (calling alSourcePlayv(nlinkedsources_,linkedsources_)) and
> actually hearing it playing at the speaker.
> The sample contains information from the very first sample, so there is no
> silence in the beginning of the sample.
>
> The length of the samples are about 0.3-0.5seconds (they are used for
> impact sounds).
>
> Now when working with recording (homestudio) I remember that the
> buffersize is rather important for the ASIO devices and stuff...
> Anything more than 8ms will give you a strange sensations of rubberstrings
> when playing a guitar and listening through the ASIO device.
>
> Is there something similar here? Is there somewhere a buffer that needs to
> be filled before the sound is actually played through the speakers?
> Some global setting for OpenAL? In the drivers for the card?
>
> Is there difference between using HW drivers for OpenAL or not?
> Or is it inside Multimedia stuff in Windows?
>
> /Anders
>
>
>
>
>
>
> --
>
>
> ________________________________________________________________
> Anders Backman Email: *andersb at cs.umu.se* <andersb at cs.umu.se>
>
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-- 


________________________________________________________________
Anders Backman               Email:    andersb at cs.umu.se
HPC2N/VRlab                  Phone:    +46 (0)90-786 9936
Umea university              Cellular: +46 (0)70-392 64 67
S-901 87 UMEA SWEDEN         Fax:      +46 90-786 6126
                               http://www.cs.umu.se/~andersb
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