Question about Jetson NVDEC non-blocking bahavior

[kazunori.kimura]

Hello

I have question about Jetson video decoder with non-blocking mode.
In 00_video_decode example, function decoder_polling_fcn has folloing code.

    while (!ctx->got_error && !ctx->dec->isInError())
    {
        /* wait on polling semaphore */
        sem_wait(&ctx->pollthread_sema);

        if (ctx->got_eos)
        {
            cout << "Decoder got eos, exiting poll thread \n";
            return NULL;
        }

        devicepoll.req_events = POLLIN | POLLOUT | POLLERR | POLLPRI;

        /* This call shall wait in the v4l2 decoder library.
           Refer V4L2_CID_MPEG_VIDEO_DEVICE_POLL */
        ctx->dec->DevicePoll(&devicepoll);

        /* We can check the devicepoll.resp_events bitmask to see
           which events are set. */
        sem_post(&ctx->decoderthread_sema);
    }

And, NvVideoEncoder.hpp::DevicePoll has these document.

   /**
    * Issues Poll on the device which blocks until :
    * a) Either there is something to dequeue from capture or output plane or any events.
    * b) Poll was interrupted by a call to the device using V4L2_CID_SET_POLL_INTERRUPT
    * c) Application has already interrupted polling by V4L2_CID_SET_POLL_INTERRUPT
    */
   int DevicePoll(v4l2_ctrl_video_device_poll *devicepoll);

I think that POLLIN indicates capture plane has something to dequeue. And POLLOUT indicates
output plane has something to dequeue. Is my understanding correct?
And, what is POLLPRI means?

regards.

[DaneLLL]

Hi,
Please refer to the discussion in
linux - difference between POLLIN and POLLPRI in poll() syscall - Stack Overflow

[kazunori.kimura]

Thank you.

I could confirm that POLLPRI event had occurred before V4L2_EVENT_RESOLUTION_CHANGE.