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Topic: Excessive latency on Windows XP

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  1. #1

    Excessive latency on Windows XP

    V2.50.46 on Windows XP
    Audio: Delta 66
    MIDI: Soundblaster Vibra 128(?)

    I have just installed Gigastudio 160 on Windows XP, and unfortunately the latency is simply too great for me to tolerate. I haven\'t measured it yet, but it feels like it\'s appreciably greater than it is when runnning Windows ME on the same hardware configuration.

    Has anyone else noticed that the latency has increased quite a lot when running on Windows XP? Are there any things I can do to improve it?

    Thanks,
    Greg.

    [This message has been edited by Greg Sullivan (edited 12-26-2001).]

  2. #2

    Re: Excessive latency on Windows XP

    Yes, the latency is greater under XP than 9x. I measured about 20ms for XP vs. 10ms on 9x for an M-Audio Audiophile on a 1GHz PIII. And no, there isn\'t much you can do about it short of getting a much, much faster computer.

  3. #3

    Re: Excessive latency on Windows XP

    The speed of the computer (read: CPU) probably has nothing to do with it. The reason is probably more likely that Win2K/XP doesn\'t allow direct \'hardware hit\' the way 98 does. I am not sure how low WDM can go regarding latency, but below 20ms should surely be possible Maybe it is something that can be improved in a later GS update.

  4. #4

    Re: Excessive latency on Windows XP

    Can you tell me the process you go through to determine your Latency?
    I would also like to test Latency my Win XP/Gigastudio system.
    Thanks , Ken

  5. #5

    Re: Excessive latency on Windows XP

    (Sigh!) The speed of the cpu has a lot to do with the latency. First off, the transitions between kernel mode (ring 0) and user mode (ring 3) are faster with a faster clock speed. This is the biggest speed hit under WDM. Second, a software synthesizer, which is how I assume Gigastudio is implemented under XP, has to go through Kmixer, which a kernel mode software mixer and sample rate converter. A faster cpu means faster routing through Kmixer. Third, DMA buffers can get filled faster with a faster cpu, which means you can use smaller buffers, thus lowering the latency. Does all this mean doubling the cpu speed will cut the latency in half? No! You\'ll get maybe a 3:2 correlation between cpou speed and latency reduction, but it will be reduced.

    For an explanation on how I measured latency on my test machine, see this thread: http://www.northernsounds.com/ubb/NonCGI/Forum1/HTML/000674.html

  6. #6

    Re: Excessive latency on Windows XP



    [This message has been edited by killerbobjr (edited 12-25-2001).]

  7. #7

    Re: Excessive latency on Windows XP

    Gaack!!! I can\'t believe I just triple posted this reply!

    [This message has been edited by killerbobjr (edited 12-25-2001).]

  8. #8

    Re: Excessive latency on Windows XP

    For me latency is better with XP than 98. This has something to do with the drivers for my MOTU2408mkII. They allow a smaller buffer with XP and therefor latency is smaller.

  9. #9

    Re: Excessive latency on Windows XP

    Hello All,

    Interesting thread - first of all, to clear up some perceptions about kernel mode and user mode - GigaStudio is a kernel mode application. The Kmixer in Xp is not used at all by GigaStudio. This is the main reason that the SoundBlaster family is not supported. The kernel mode interface is the GSIF implementation of the supported sound hardware.

    About WDM - again, a sound card driver can be VxD or WDM, but it must have a GSIF implementation to work with GigaStudio. This provides for the lowest latency.

    Apart from this, there are two other factors that contribute to latency:


    1. Buffer settings in the sound hardware driver control panel.

    2. Hard disk streaming effeciency. DMA settings, cache size, cluster size, and fragmentation all contribute to the amount of time it takes to stream samples off the hard disk.

    Hope this helps,

    Kevin

  10. #10

    Re: Excessive latency on Windows XP

    Have you guys made a lot of measurements on the latency of the MIDI input through a hardware port under XP compared to Win9x with various hardware? The tests I\'ve done on the two useful pieces of hardware I have here at the bunker (the MIDI in of a M-Audio Audiophile and an MPU-401) show a significant increase between Win9x and XP. Also, even with every single service stopped and file system cache set to the minimum (I\'m still trying to find a way to turn it completely off), GS under XP requires quite a bit more horsepower to reach the same performance levels that it attains under Win9x.

    The one positive thing I can say about XP is that 99% of GS buyers will be able to have hassle free, out-of-the-box 160 voice performance with no tweaking at all using decent hardware (1GHz min, 256MB ram).

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