Results 1 to 2 of 2

Thread: Irregular DirectShow timestamps from DFG/USB2-lt

  1. #1
    Join Date
    Jan 2013
    Posts
    1

    Irregular DirectShow timestamps from DFG/USB2-lt

    Hello,

    I have a DirectShow capture graph where an analog NTSC video source is streamed to an MPEG2 encoder.

    Using a third party analog capture card, the graph works fine. If I inspect the media samples coming from the capture source, the timestamps are always about 0.0333667 seconds apart, which is expected for 29.97 fps NTSC video.

    When I try the graph with my DFG/USB2-lt capture device, the resulting video seems intermittently jerky. Inspection of the media sample timestamps shows a pattern of 0.0322 seconds between samples, with the occasional 0.046 gap every 10-20 samples.

    My guess would be that this timestamp irregularity is causing the jerkiness in the video. Why are samples being timestamped like this?

    (I thought it might be that frames are being dropped, but I would think that I'd see a multiple of the regular frame duration in that case. The samples aren't being marked as discontinuities, either, and I also tried reducing the resolution to make dropped frames less likely, but that didn't change the timestamp behavior.)

  2. #2
    Join Date
    Jan 2003
    Location
    Bremen, Germany
    Posts
    4,862

    Re: Irregular DirectShow timestamps from DFG/USB2-lt

    Hello

    The gabs are usual, and there was a reason for them. (Sorry, but I forgot the reason.)

    The time stamps are generated in the computer by the driver, when the USB controller notifies the driver, that there is a new image.
    Best regards
    Stefan
    IC Imaging Control Support

Similar Threads

  1. the DFG/USB2-ltpcb and DFG/USB2-lt support for VB6??
    By kayma in forum IC Imaging Control .NET
    Replies: 1
    Last Post: January 3, 2011, 10:57:13
  2. DMK31 USB2 on ICCapture 2.1
    By maxellwill in forum Astronomy Cameras Support Forum
    Replies: 2
    Last Post: October 1, 2010, 17:31:12
  3. Linux driver for DFG/USB2-lt
    By darkwing in forum IC Imaging Control C++ Class Library
    Replies: 1
    Last Post: May 8, 2009, 15:35:05
  4. DFG/USB2-It and colour
    By glennpierce in forum IC Imaging Control C++ Class Library
    Replies: 1
    Last Post: October 17, 2007, 14:31:01
  5. Timestamps - getCurReferenceTime() and tsMediaSampleDesc structure members
    By FSeiler in forum IC Imaging Control C++ Class Library
    Replies: 0
    Last Post: August 9, 2007, 20:03:25

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •