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What does Region of Interest do in the IPNC RDK on the DM8127?

Dave Beal
Intellectual 880 points

I'm using the IPNC RDK 3.5 on a custom DM8127 board.  I've been asked to investigate the Region of Interest feature, but I haven't found any documentation on it.  I've experimented by sending the ENC_LINK_CMD_SET_CODEC_ROI link control to the H.264 encoder; my parameters seem to get sent to the encoder, but nothing appears to change in the encoded stream.

What does the ROI feature do, and how is it used?  Thanks!

  • 0
    TI__Expert 8920 points

    Hi,

    ROI feature encodes ROI with more bits then rest of region.

    Can you pl. reduce the bitrate and observe that ROI to be more clear then rest of region?

    regards,

    Anand

  • 0 in reply to Anand Kulkarni71405
    Intellectual 880 points

    Thank you for your reply, Anand.  I'm encoding a 1920x1080p30 stream at 1.5Mbps, and so far I haven't seen anything happen when I enable a region of interest.  I'm setting the ROI parameters to startX=0, startY=0, width=900, height=500, type=2 (ROI_FOREGROUND_TYPE). I'm assuming that this will make approximately one quadrant of the video frame into an ROI.   I've also tried type=0 (ROI_FACE_TYPE) with no apparent result.

    Which corner of the frame is x=0, y=0?  And what does the type parameter do?  Thanks!

  • 0 in reply to Dave Beal
    TI__Prodigy 560 points

    Dave,

    I think the fast way you understand about how ROI work is to refer to the source code included in the RDK,

    If you could make RDK3.5 work on your board, please go to web GUI/Video/Advanced,

    check the box of 'Enable Region of Interest', and specify the area you want to make as a ROI region,

    clock 'OK' and look what will happen to the stream,

    the related source code is in encLink_h264.c, please search 'ENC_LINK_SETCONFIG_BITMASK_ROI',

    you need to pay attention that:

    1.ROI area will have more obvious good quality compared to the other area

    when you make bitrate quite low, in your case(1080p30), make you stream under 1Mbps,

     you can tell the difference by seeing with your eyes.

    2.you can check with some h.264 stream analyzer like vega or elecard, you'll definitely get a better understanding about

     how much qp will be improved in your specified ROI region. 

  • 0 in reply to Mingda Shen
    Intellectual 880 points

    Thank you, Mingda.  I can now see that the ROI feature does produce a small visible effect, but you have to be looking for it to see it.  For my 1080p30 stream, I can see the effect at bitrates from 200Kbps to about 1.5Mbps.  It shows up mostly as a slight reduction in noise along high-contrast edges in the ROI region.  The type of ROI enabled (face/foreground/background/default) didn't seem to make any difference.