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Display using V4L2 without color conversion

Pierre-Olivier Belzile
Intellectual 375 points

I'm using V4L2 to display a videostream in YUY422 (YUYV) format. The output port is configured for embedded sync and automatically convert the pixel values from the 8-bit 0-255 range to 16-235 range. Is there a way to disable this compression ? According to VPSS user guide, there doesn't seems to be any ioctrl to control that feature... 

Any idea of how to disable this ?

Pierre-Olivier

  • 0
    TI__Mastermind 20245 points

    Hi,

    You can set the HDMI in discrete sync mode, but discrete sync mode wont work with interlaced output, here is the way to change it to discrete sync mode,

    echo 0 > /sys/devices/platform/vpss/display0/enabled

    echo triplediscrete,rgb888,0/0/0/0/ > /sys/devices/platform/vpss/display0/output

    echo 1 > /sys/devices/platform/vpss/display0/enabled

  • 0 in reply to HardikShah
    Intellectual 375 points

    Actually i'm working on a 16-bit bus. Both embedded and discrete sync have the same behavior:

    echo "double,yuv422spuv,0/0/0/0" > /sys/devices/platform/vpss/display1/output

    echo "doublediscrete,yuv422spuv,0/0/0/0" > /sys/devices/platform/vpss/display1/output

    The buffer passed to v4l2 is converted from 0-255  to 16-235 (Y pixel value). 

    In V4L2 I use the following:

    /* Set the image size to 1920x1080 and pixel format to YUV422 */
    fmt.fmt.pix.width = m_Width;
    fmt.fmt.pix.height = m_Height;
    fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
    ret = ioctl(m_display_fd, VIDIOC_S_FMT, &fmt);

    Can I disable that conversion ?