USB Latency ?
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Thread: USB Latency ?

  1. #1
    Tech Wizard
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    Default USB Latency ?

    Hi

    Just wondering, heard something about that the USB port, has a minumum latency at 3,6ms, no matter what kind of USB equipment you are using or how low Traktors own latency can go..

    Just an ex here...

    When i hit play on my VCI-100, then it will take 3,6ms to reach Traktor and make a response, then it will send the signal to the USB soundcard, Audio DJ8,
    and then again it will take 3,6ms to reach the speakers..

    so the conclusion is, it will take 7,2 ms from button to speakers, even if Traktor is running at 1ms.. ?
    accually it will be 8,2ms with the Traktors 1ms :-)
    Am I all wrong here???

  2. #2
    Tech Guru charo's Avatar
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    while i don't know if those numbers are correct, you are correct in thinking that the total latency of the system is going to be higher then the latency listed in the tracktor latency. the total latency of the system is going to be a combination of factors, like the computer specs, soundcard specs, midi controller specs in regard to the total picture.

    i do believe a usb soundcard is going to add a little more latency then a firewire card, esp if are also using a usb midi controller.

    But I think a person can get all wrapped up in having the lowest possible latency, when really what is important is a consistency. if one time you hit a button and you get 10ms of latency and the next time you hit a button and you get 15ms of latency then you can't plan for it like you can with a solid consistent latency. Alot of music making devices have some type of latency when you think about it, the musican learns to work with it.

    deeper down on the production side of things, some people can't stand modern computers implementation of midi to the degree that they stick with hardware sequencers and/or still use atari computers, with midi in/outs that are directly attached to the motherboard.


    also i'm not sure on that part where it takes 3.6ms for the sound to go from the soundcard to the speakers.
    We don't believe in the star system. We want the focus to be on the music. If we have to create an image, it must be an artificial image. That combination hides our physicality and also shows our view of the star system. It is not a compromise-daftpunk

  3. #3
    Tech Wizard
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    It will take a bit longer actually because you forgot the digital to analog conversion in your soundcard in your equation witch usualy takes some time ;-)

  4. #4
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    Quote Originally Posted by cuttymello View Post
    It will take a bit longer actually because you forgot the digital to analog conversion in your soundcard in your equation witch usualy takes some time ;-)
    That time is so small that in practice you can simply say it doesn't happen.

    Think of it... in classic DA conversion at 44100 each sample lasted 1/44100 seconds. That's about 40 times less than a millisecond which is 1/1000.

    Nowadays convertors like 1bit Sigma Delta modulation, work well above the Nyquist rate (around 8Mhz or 1/8000000 seconds) and then accumulate the data into 44100, or 96000 or whatever sample frequency you want.

    This is why hardware monitoring in your audio interface has zero latency. It's not zero, but for any human it's too fast to be noticed.

    This is also why you really need an accurate clock to have good AD/DA conversion, and why good clocks cost thousands of dollars.

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