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  1. Path: sparky!uunet!convex!darwin.sura.net!sgiblab!sdd.hp.com!elroy.jpl.nasa.gov!ames!sun-barr!news2me.EBay.Sun.COM!seven-up.East.Sun.COM!sungy!news.Sweden.Sun.COM!swippy!seunet!sunic!dkuug!uts!unilrh
  2. From: unilrh@uts.uni-c.dk (Leif R|dgaard)
  3. Newsgroups: comp.sys.sgi
  4. Subject: synchronization problems using IndigoVideo Board
  5. Message-ID: <UNILRH.92Nov13163133@uts.uni-c.dk>
  6. Date: 13 Nov 92 16:31:33 GMT
  7. Sender: unilrh@uts.uni-c.dk (Leif R|dgaard)
  8. Distribution: comp.sys.sgi
  9. Organization: UNI-C, Danish Computing Centre for Research and Education
  10. Lines: 28
  11.  
  12. We have access to an Indigo with VideoBoard and Svideo-software, 
  13. an with this we want to make a couple of minutes VHS PAL-video.
  14.  
  15. With the equipment is it easy to make live-video-in and live-video-out,
  16. but we are unable to make single-frame output (because we are unable
  17. to control the VCR from the Indigo).
  18.  
  19. So we do 384x288 (1/4 PAL-area) live-video from our own GL-program, and here
  20. we can show 60 frames/sec from data in memory. This limits us to about 
  21. 20 seconds per recording, but we hope to be able to load pictures from
  22. disk fast enough.
  23.  
  24. The program uses double-buffering (GL swapbuffers()), where our problem is
  25. to synchonize the swapping of frames to the PAL-signal. The animation is
  26. fine on Indigo-screen, but the recording on VCR is jagged.
  27.  
  28. How do we swap framebuffers during PAL vertical retrace (preferably controlled
  29. by interrupts instead of polling). ???
  30. -- 
  31. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  32. +    Leif R|dgaard Hansen                                               +
  33. +    UNI-C Lyngby, Danish Computing Center for Research and Education.  +
  34. +    DTH, building 305, DK 2800 Lyngby                                  +
  35. +    Phone: +45-45.93.83.55                                             +
  36. +    Fax:   +45-45.93.02.20                                             +
  37. +                                                                       +
  38. +    E-Mail: unilrh@unisgi.uni-c.dk                                     +
  39. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  40.