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VIDIX - VIDeo Interface for nix
Guest on 9th February 2023 02:13:26 PM


  1.                 VIDIX - VIDeo Interface for *niX
  2.                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  3.  
  4. This interface was designed and introduced as interface to userspace drivers
  5. to provide DGA everywhere where it's possible (unline X11).
  6. I hope that these drivers will be portable same as X11 (not only on *nix).
  7.  
  8. What is it:
  9. - It's portable successor of mga_vid technology which is located in user-space.
  10. - Unlikely X11 it's provides DGA everywhere where it's possible.
  11. - Unlikely v4l it provides interface for video playback
  12. - Unlikely linux's drivers it uses mathematics library.
  13.  
  14. Why it was developed:
  15. As said Vladimir Dergachev
  16. (http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/gatos/km/km.rfc.txt):
  17. "0) Motivation
  18.     v4l, v4l2 and Xv are all suffering from the same problem: attempt to fit
  19.     existing multimedia devices into a fixed scheme."
  20. Well - I tried to implement something similar by motivation.
  21.  
  22. How it works:
  23. ~~~~~~~~~~~~~
  24.  
  25. This interface is almost finished. But I guess it can be expanded by developer's
  26. requests.
  27. So any suggestions, reports, criticism are gladly accepted.
  28.  
  29. 1) APP calls vixGetVersion to check age of driver ;)
  30. 2) APP calls vixProbe. Driver should return 0 if it can handle something in PC.
  31. 3) APP calls vixGetCapability. Driver should return filled
  32.     vidix_capability_t.type field at least.
  33. 4) If above calls were succesful then APP calls vixInit function
  34.    (Driver can have not exported this function in this case call will be
  35.     skiped).
  36. 5) After initializing of driver APP calls vixGetCapability again
  37.    (In this case driver must fill every field of struct)
  38. 6) APP calls vixQueryFourcc. Driver should answer - can it configure
  39.    video memory for given fourcc or not.
  40. 7) APP calls vixConfigPlayback. Driver should prepare BES on this call.
  41.    APP pass to driver following info:
  42.    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  43.    vidix_playback_t.fourcc      - contains fourcc of movie
  44.    vidix_playback_t.capability  - currently contsinas copy of vidix_capability_t.flags
  45.    vidix_playback_t.blend_factor- currently unused
  46.    vidix_playback_t.src         - x,y,w,h fields contain original movie size
  47.                                   (in pixels) x and y often are nulls.
  48.    vidix_playback_t.src.pitch.y   These fields contain source pitches
  49.    vidix_playback_t.src.pitch.u - for each Y,U,V plane in bytes.
  50.    vidix_playback_t.src.pitch.v   (For packed fourcc only Y value is used)
  51.                                   They are hints for driver to use same destinition
  52.                                   pitches as in source memory (to speed up
  53.                                   memcpy process).
  54.                                   Note: when source pitches are unknown or
  55.                                   variable these field will be filled into 0.
  56.    vidix_playback_t.dest        - x,y,w,h fields contains destinition rectange
  57.                                   on the screen in pixels.
  58.    vidix_playback_t.num_frames  - maximal # of frames which can be used by APP.
  59.                                   (Currently 10).
  60.    Driver should fill following fields:
  61.    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  62.    vidix_playback_t.num_frames  - real # of frames which will be used by driver.
  63.                                   (Should be less or equal to app's num_frames).
  64.  
  65.    vidix_playback_t.dest.pitch.y   These fields should contain alignment
  66.    vidix_playback_t.dest.pitch.u - for each Y,U,V plane in bytes.
  67.    vidix_playback_t.dest.pitch.v   (For packed fourcc only Y value is used)
  68.  
  69.    vidix_playback_t.frame_size  - Driver should tell to app which size of
  70.                                       source frame (src.w and src.h) should
  71.                                       use APP (according to pitches and offsets)
  72.  
  73.    vidix_playback_t.offsets     - offsets from begin of BES memory for each frame
  74.  
  75.    vidix_playback_t.offset.y      These field should contain offset
  76.    vidix_playback_t.offset.u    - for each Y,U,V plane within frame.
  77.    vidix_playback_t.offset.v      (For packed fourcc only Y value is used)
  78.  
  79.    vidix_playback_t.dga_addr    - Address of BES memory.
  80.  
  81. Also see this picture:
  82.  
  83. VIDEO MEMORY layout:
  84.  +-----------  It's begin of video memory     End of video memory--------------+
  85.  |                                                                             |
  86.  v                                                                             v
  87.  [      RGB memory                         |         YUV memory    |  UNDEF    ]
  88.                                            ^
  89.                                            |
  90.                                            +---- begin of BES memory
  91.  
  92. BES MEMORY layout:
  93.  +-------- begin of BES memory
  94.  |
  95.  v
  96.  [ | |                      |       |       |
  97.    ^ ^                      ^       ^       ^
  98.    | |                      |       |       + BEGIN of second frame
  99.    | |                      |       + BEGIN of V plane
  100.    | |                      + BEGIN of U plane
  101.    | +------- BEGIN of Y plane
  102.    |
  103.    +--------- BEGIN of first frame
  104.  
  105. This means that in general case:
  106. offset of frame != offset of BES
  107. offset of Y plane != offset of first frame
  108.  
  109. But often: vidix_playback_t.offsets[0] = vidix_playback_t.offset.y = 0;
  110.  
  111. Formula: (For Y plane) copy source to:
  112.                   vidix_playback_t.dga_addr +
  113.                   vidix_playback_t.offsets[i] +
  114.                   vidix_playback_t.offset.y
  115.  
  116. 8) APP calls vixPlaybackOn. Driver should activate BES on this call.
  117. 9) PLAYBACK. Driver should sleep here ;)
  118.    But during playback can be called:
  119.      vixFrameSelect (if this function is exported)
  120.         Driver should prepare and activate corresponded frame.
  121.         This function is used only for double and trilpe buffering and
  122.         never used for single buffering playback.
  123.      vixGet(Set)GrKeys (if this function is exported)
  124.         This interface should be tuned but intriduced for overlapped playback
  125.         and video effects (TYPE_FX)
  126.      vixPlaybackGet(Set)Eq (if this function is exported)
  127.         For color correction.
  128. 10) APP calls vixPlaybackOff. Driver should deactivate BES on this call.
  129. 11) If vixDestroy is defined APP calls this function before unloading driver
  130.     from memory.
  131.  
  132.  
  133. What functions are mandatory:
  134. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  135. vixGetVersion
  136. vixProbe
  137. vixGetCapability
  138. vixQueryFourcc
  139. vixConfigPlayback
  140. vixPlaybackOn
  141. vixPlaybackOff
  142.  
  143. All other functions are optionaly.
  144.  
  145. Useful links:
  146. ~~~~~~~~~~~~~
  147. Guide to DTV            http://www.digitaltelevision.com/dtvbook/toc.shtml
  148. Fourcc                  http://www.webartz.com/fourcc/
  149. MPEG                    http://www.mpeg.org/MPEG/index.html
  150. Analog colors           http://www.miranda.com/en/app_notes/TN/TN-05/TN-05.htm
  151.  
  152. Please send your suggestions, reports, feedback to mplayer-dev-eng@mplayerhq.hu
  153. Best regards! Nick Kurshev.

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