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aspeed-video.rst

aspeed-video.rst 2.1 KB
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  1. .. SPDX-License-Identifier: GPL-2.0
    2. 

  2. 

  3. .. include:: <isonum.txt>
    4. 

  4. 

  5. ASPEED video driver
    6. 

  6. ===================
    7. 

  7. 

  8. ASPEED Video Engine found on AST2400/2500/2600 SoC supports high performance
    9. 

  9. video compressions with a wide range of video quality and compression ratio
    10. 

  10. options. The adopted compressing algorithm is a modified JPEG algorithm.
    11. 

  11. 

  12. There are 2 types of compressions in this IP.
    13. 

  13. 

  14. * JPEG JFIF standard mode: for single frame and management compression
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  15. * ASPEED proprietary mode: for multi-frame and differential compression.
    16. 

  16.   Support 2-pass (high quality) video compression scheme (Patent pending by
    17. 

  17.   ASPEED). Provide visually lossless video compression quality or to reduce
    18. 

  18.   the network average loading under intranet KVM applications.
    19. 

  19. 

  20. VIDIOC_S_FMT can be used to choose which format you want. V4L2_PIX_FMT_JPEG
    21. 

  21. stands for JPEG JFIF standard mode; V4L2_PIX_FMT_AJPG stands for ASPEED
    22. 

  22. proprietary mode.
    23. 

  23. 

  24. More details on the ASPEED video hardware operations can be found in
    25. 

  25. *chapter 6.2.16 KVM Video Driver* of SDK_User_Guide which available on
    26. 

  26. `github <https://github.com/AspeedTech-BMC/openbmc/releases/>`__.
    27. 

  27. 

  28. The ASPEED video driver implements the following driver-specific control:
    29. 

  29. 

  30. ``V4L2_CID_ASPEED_HQ_MODE``
    31. 

  31. ---------------------------
    32. 

  32.     Enable/Disable ASPEED's High quality mode. This is a private control
    33. 

  33.     that can be used to enable high quality for aspeed proprietary mode.
    34. 

  34. 

  35. .. flat-table::
    36. 

  36.     :header-rows:  0
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  37.     :stub-columns: 0
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  38.     :widths:       1 4
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  39. 

  40.     * - ``(0)``
    41. 

  41.       - ASPEED HQ mode is disabled.
    42. 

  42.     * - ``(1)``
    43. 

  43.       - ASPEED HQ mode is enabled.
    44. 

  44. 

  45. ``V4L2_CID_ASPEED_HQ_JPEG_QUALITY``
    46. 

  46. -----------------------------------
    47. 

  47.     Define the quality of ASPEED's High quality mode. This is a private control
    48. 

  48.     that can be used to decide compression quality if High quality mode enabled
    49. 

  49.     . Higher the value, better the quality and bigger the size.
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  50. 

  51. .. flat-table::
    52. 

  52.     :header-rows:  0
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  53.     :stub-columns: 0
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  54.     :widths:       1 4
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  55. 

  56.     * - ``(1)``
    57. 

  57.       - minimum
    58. 

  58.     * - ``(12)``
    59. 

  59.       - maximum
    60. 

  60.     * - ``(1)``
    61. 

  61.       - step
    62. 

  62.     * - ``(1)``
    63. 

  63.       - default
    64. 

  64. 

  65. **Copyright** |copy| 2022 ASPEED Technology Inc.
    66.