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DM8148 Video Capture Polling Interval

AlexB
Prodigy 50 points

We are using the EZSDK on the 8148 and noticed the video buffers are being returned form the capture driver at multiples of 8 msec.   This results in 60 Hz video being received at intervals of 16, 16, 16, 24, ...    I have seen some other posts suggesting ways to change this but they all seem to be relative to the RDK.   Ideally it would be interrupt driven capture and not polled at all, but if that isn't possible at least reducing the polling interval would make a big difference.   

  • 0
    TI__Guru**** 478335 points

    It is not possible to change from polling based mechanism to interrupt, it is big change..

    what is the problem? is it the timestamp? or something else?

    we can reduce the polling frequency, but again, after every x number of frames, you will see difference of 4ms..

    Another way to solve is to enable slice based processing, in this, you could get the callback as soon as frame is captured, you could use this frame, but you cannot deueue it.

    Regards,

    Brijesh

  • 0 in reply to Brijesh Jadav
    Prodigy 50 points
    The variability on the input timing of video frames makes our whole system more susceptible to other slight differences in timing. In one example we capture video, run some algorithms, and then output the video on HDMI and we are seeing missed and duplicate frames on the HDMI output. The capture variability isn't the only issue but if we can solve that it will make everything else more straight forward.

    It sounds like dropping the polling frequency to 4 and maybe also looking at slice based processing would be a good start. Can you provide information on how to make these changes? The slice based processing I think would be enough in itself, if that allows us to get callbacks as soon as the frame is captured.
  • 0 in reply to AlexB
    TI__Guru**** 478335 points
    Hi,

    For changing polling interval, you would require hdvpss source.. do you have access to the hdvpss source?

    Regards,
    Brijesh
  • 0 in reply to Brijesh Jadav
    Prodigy 50 points
    Hi Brijesh,

    We do have access to the hdvpss source.
  • 0 in reply to AlexB
    TI__Guru**** 478335 points

    ok, in that case, change value of the macro 

    VPS_CAPT_LIST_UPDATE_TIME_IN_TICKS

    from 8 to 4

    in pspdrivers_\packages\ti\psp\vps\drivers\capture\vpsdrv_captureLm.h file.

    and rebuild hdvpss.

    Regards,

    Brijesh

  • 0 in reply to Brijesh Jadav
    Prodigy 50 points
    Thanks - that worked. I may look into changing to slice based in the future but for now reducing the input variability should help a lot.