Playing a video using the USB 3.0 port?

Discussion in 'Amateur Video Production' started by Brian, May 29, 2013.

  1. Brian

    Brian Guest

    Now that USB 3.0 claims to be 10 times faster than USB 2.0 then is it
    possible to playback in the video editor a movie on an external hard drive
    such as someone wanting to edit the video from the external hard drive?
    I'm also thinking that the data transfer rate of the external hard drive
    could still limit this if its possible to playback the video.
    The type of video I'm referring to is what is recorded on the internal
    memory of the video camera.

    The reason I'm using is that I'm thinking of getting a USB 3.0 card for my
    computer and the internal hard drive sometimes has less hard drive space.
    Brian, May 29, 2013
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  2. Brian

    Paul Guest

    Yes, using USB3 will remove the bottleneck caused by USB2.

    No question about that.

    You will see some improvement. At least a factor of 3 or so. Maybe more.


    USB2 operates around 30MB/sec in terms of sustained transfer rate.

    The bare hard drive, can do roughly 125MB/sec for a commodity drive
    purchased today. The very best hard drive, can do 180MB/sec
    sustained ( some WD 600GB drive does that ).

    If the hard drive needs to do "random access", moving the head around
    a lot, to get data from several files, then the hard drive performance
    will drop to quite a low level. The only time you get the 125MB/sec
    number, is under ideal conditions, such as playing back a movie
    that you've finished editing. If you're combining several files
    in an editing session, if that requires rapid hard drive head
    movement, you'll won't get even close to 125MB/sec then.

    So the hard drive, has a "seek time". That's the time to move the
    heads around. No data is transferred during the time the heads
    move a significant distance. And that might be 12 milliseconds.

    If you get an SSD drive, which is based on Flash memory, that
    improves the seek time. SSD over USB2, seek is 1 millisecond.
    SSD over SATA (any flavor), is around 0.1 millisecond. The
    difference, is the slowness of polled protocols on USB2.

    I don't have a seek penalty number for USB3, but it should be
    slightly better than the 1 millisecond number, and be sub-millisecond.
    It cannot match the SATA time of 0.1 millisecond though, because
    there are two delays in a row (SATA_Delay + USB3_Delay).

    A decent hard drive enclosure, the USB3 to SATA chip in it, should
    be able to do 200MB/sec (you see that speed, only when a good SSD
    is connected to it). And that means, no existing hard drive
    would be held up, by the USB3 interface. The 200MB/sec enclosure,
    will not be a bottleneck for the 125MB/sec hard drive you bought
    for $100.


    The USB3 plug on your new add-in card, has both USB3 pins and
    USB2 pins. When you plug a USB2 device into the USB3 port, just
    the USB2 pins make contact. If you plug in a USB3 capable device,
    then the USB3 pins are touching, and then the devices can agree
    to use the USB3 speeds. So you can still "use a USB2 device in a
    USB3 hole". And on the vice-versa side, you can plug a USB3 device
    into a USB2 hole, as again, the USB2 pins touch.

    If you run USB2 over USB3 protocol, you can actually get a slight
    bit more performance, even for the USB2 bottleneck. I have a
    USB3 flash stick, and it does around 35MB/sec over USB2. Which
    is better than the 30MB/sec a USB2 flash stick does over USB2.
    And I don't know why it does that :)


    You will need an open PCI Express x1, x4, x8, or x16 slot
    for the new card. The x1 is the "exact fit" for the card,
    while the other slots will still accept the card (left over

    PCI Express motherboard slots, come in 250MB/sec and 500MB/sec
    flavors. That's for the available generations of PCI Express
    lanes. Having the 500MB/sec x1 slot, is more rare than the
    common 250MB/sec slot. The USB3 *could* work a bit faster,
    if the motherboard has 500MB/sec lanes, but it should still
    work well enough for what you want to do. My slots are
    the 250MB/sec kind, for example.

    If you plugged the new add-in card, to a 500MB/sec lane,
    then the max you can reasonably expect from USB3 is around
    336MB/sec. But no enclosure goes that fast yet. The 200MB/sec
    would be a good enclosure, and there are probably a few
    older USB3 enclosures still slower than that. If buying
    an enclosure, it helps to check customer reviews, for
    a benchmark test result.


    One unknown, is the PCI Express bus performance, due to buffer
    size. While the nominal lane speed is 250MB/sec or 500MB/sec,
    that "goodput performance" (your *actual* transfer speed)
    is subject to the size of the packet buffers in the chipset.
    For a badly designed chipset, you can actually chop the
    transfer rate in half. So if you didn't get stellar numbers,
    there is still an explanation for it based on the PCI Express
    implementation of your motherboard chipset.

    For example, if my Intel chipset motherboard uses 64 byte buffers
    for the PCI Express packets, the efficiency is 0.59 to 0.63. See
    page 2, for the graph. Pessimistically, we could guess around
    250MB/sec * 0.63 = 158MB/sec, still faster than the commodity
    hard drive, but not by much.

    It's still a decently matched system, which is why I feel
    you could get 3x more performance, pretty well guaranteed.
    Any more than that, there are a few issues to check out.
    Like, if you're sticking an SSD in your USB3 enclosure,
    then you'd want to pay a lot more attention to those
    tiny details (to get a nice benchmark number). With a
    hard drive, the hard drive is a slouch, and makes the
    other details less significant.

    Paul, May 29, 2013
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  3. If you are saying that you are playing the video directly from the
    camera, you won't see a change unless the camera itself has a USB3

    USB2 and 3 are compatible, but to get USB3 speeds, the port, the device,
    *and the cable* must all be USB3 hardware.

    If instead you are copying the files to a USB3 hard drive before working
    with it, then the speeds will be good *and* I apologize for being
    confused :)
    Gene E. Bloch, May 29, 2013
  4. Brian

    j Guest

    Since no one else has mentioned this, any movies you will be likely
    playing back will be compressed, 3.5MB/sec or less.

    Note that some webcams do move raw video over USB, which can be quite
    taxing. But generally video is stored compressed in some format, not raw.

    Thanks to Paul for all the info...

    j, May 29, 2013
  5. Brian

    Brian Guest

    Hi Gene.

    I just wanted to use the external hard drive instead of the internal hard
    drive when editing a movie. It's good to know that it can be done.
    Brian, May 30, 2013
  6. Brian

    Brian Guest

    matched system, which is why I feel
    Thanks Paul for the useful information.
    Brian, May 30, 2013
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