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[FAQ]: How to configure DSS for BT656 or BT1120 output format?

Brijesh Jadav
Guru**** 436525 points

Part Number: PROCESSOR-SDK-DRA8X-TDA4X

Many of the LCDs and encoders accept the video over BT656 or BT1120 format. How t0 change PSDKRA to configure DSS for BT656 and BT1120 output format?

  • 0
    TI__Guru**** 436525 points

    PSDKRA by default support discrete sync output for DPI output. But many of the LCDs and encoders supports video over only BT656 or BT1120 input. This require change in PSDKRA to configure DSS for BT mode.
    DSS in DRA8x has Video Port (VP) module, which is used to output over BT or discrete sync interface. This module is configured in the API appDctrlDefaultInit in psdk_rtos_auto_j7_07_00_00_11\vision_apps\utils\dss\src\app_dss_defaults.c file. This API internally calls appDctrlVpParamsInit API to initialize VP parameters to default values. As part of this initialization, it also intializes output format to discrete sync output format. In order to configure DSS for BT output mode, after calling API appDctrlVpParamsInit, add a below line.
    vpParams.dvoFormat = APP_DCTRL_DV_BT656_EMBSYNC; // for BT656 output format
    vpParams.dvoFormat = APP_DCTRL_DV_BT1120_EMBSYNC; // for BT1120 output format

    The use of video parameters sligtly changes for BT output mode. The video timing for the output is specified in appInit API in the file psdk_rtos_auto_j7_07_00_00_11\vision_apps\apps\basic_demos\app_tirtos\common\app_init.c. Please find below meaning of different timing parameter for BT output mode

    • Progressive Output Format for BT656/BT1120
      • hSyncLen: This parameter is used to specify horizontal blanking, ie the number of clock cycles between EAV and SAV codes. The valid range for this parameter is from 1 to 4096 cycles and 0 is invalid. Provide value as actual sync length plus 1.
      • vBackPorch: This parameter is used to specify vertical frame blanking-1 ie blanking at the top of the active video.
      • vFrontPorch: This parameter is used to specify vertical frame blanking-2 ie blanking at the bottom of the active video.
      • hFrontPorch, hBackPorch, vSyncLen: These parameters are not used for this output format.
    • Interlaced Output Format for BT656/BT1120
      • hSyncLen: Same as progressive output, this parameter is used to specify horizontal blanking, ie the number of clock cycles between EAV and SAV codes. The valid range for this parameter is from 1 to 4096 cycles and 0 is invalid. Provide value as actual sync length plus 1.
      • vBackPorch: This parameter is used to specify vertical frame blanking-1 for the odd field ie blanking at the top of the active video for odd field.
      • vFrontPorch: This parameter is used to specify vertical frame blanking-2 for the odd field ie blanking at the bottom of the active video for the odd field.
      • hBackPorch: This parameter is used to specify vertical frame blanking-1 for the even field ie blanking at the top of the active video for odd field.
      • hFrontPorch: This parameter is used to specify vertical frame blanking-2 for the even field ie blanking at the bottom of the active video for the even field.
      • vSyncLen: This parameter is not used for this output format.

    Regards,

    Brijesh