Video duration inconsistent with Capture duration

Discussion in 'Windows Vista Drivers' started by Mini UVC UAC, Dec 3, 2009.

  1. Mini UVC UAC

    Mini UVC UAC Guest

    Hi, All:
    our device is an USB Video Device compliant with USB Video Class V1.0.
    After loaded the Microsoft InBox UVC driver, the video preview function is OK.
    But when capture video, then playback it, the capture duration is
    inconsisten with video duaration.
    for the UVC descriptor, he uncompressed YUY2 frame type decriptor
    report the each frame interval is 30fps, and our device acturally output

    But When capture the video using AMCAP or Ulead, there are no any
    dropped counts reported by the software/uvc driver. I think it is the main
    reason which lead to inconsistence.
    So whether there are some bugs about MS Inbox UVC 1.0 Driver? Who can
    give me some suggestion about how to compute the dropped counts?

    Thanks in advance.

    attached the UVC descriptor.

    Mini UVC UAC, Dec 3, 2009
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  2. Mini UVC UAC

    Tim Roberts Guest

    That's a problem, don't you think? Do you report actual timestamps in your
    Why do you think there are bugs? No frames were dropped. You are just
    delivering frames late.
    Tim Roberts, Dec 3, 2009
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  3. Mini UVC UAC

    Mini UVC UAC Guest

    Hi, Tim Roberts:

    Thanks very much for your soon reply.

    First, I have reported the actually timestamps(25fps) in the video frame
    header, even though uncompressed YUY2 frame type decriptor defined the each
    frame interval is 30fps.
    Second, we also develop ourself device driver, and report the 5 frame
    drop count per second in the reqeust KSPROPERTY_DROPPEDFRAMES_CURRENT, then
    the same problem is not produced.
    But for MS Windows inbox UVC driver, I can't see any dropped frame
    counts, and the problem happened.
    Does it mean that there are some bugs ?

    in other way, we have do the following experiment:
    if our device output the fixed frame rate 15fps, and also report the actuall
    timestamps(15fps) in the header, MS Windows inbox uvc driver will report the
    correct dropped frame counts(15 frame per second), and of course, the problem
    is also not happned.


    Mini UVC UAC, Dec 3, 2009
  4. Mini UVC UAC

    Tim Roberts Guest

    Why is the actual frame rate different than what you reported in the
    descriptor? When do you know the actual frame rate? Maybe you need to
    report a frame range in the descriptor, then report the actual rate during
    the probe and commit process.
    I doubt it. Technically speaking, no frames are being dropped. The driver
    has delivered every frame that was sent. You hardware is lying: it is
    delivering frames at a rate different from the rate you promised.
    Tim Roberts, Dec 6, 2009
  5. Mini UVC UAC

    Mini UVC UAC Guest

    Hi, Tim:
    The case which actually frame rate is different with the rate reported
    in the descritor table is very polular. and most parts of other usb cameras
    vary the frame rate according to the light exposure, in order to get better
    image quality.
    For describe the question simply and clearly, I just select the fixed
    rate 25fps as the example.
    Mini UVC UAC, Dec 7, 2009
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