NVENC - timestamps are getting swapped

Hi all,

Recently started working with the NVENC API. I’m successfully decoding N distinct h264 bits streams into NV12, resize and stitch all the frames into a final 1080p or 4K frame, and then pass this final frame to the encoder.

Some background (not really relevant to this issue, but offers some context)
For this purpose, I select one of those N input h264 streams as the “driver”: whenever the final 4K frame gets changed because of that select input stream, I shoot out a request to the NVENC to encode the fat frame (1080p or 4k).

What I do

  • For each NV12 frame about to be encoded, I associate a timestamp with the help of NV_ENC_PIC_PARAMS::inputTimeStamp
  • The encoder is setup in such a way that it does not produce B frames (NV_ENC_CONFIG::frameIntervalP == 1)
  • The timestamps are monotonically increasing in a strict way. In other words, the next-timestamp is strictly bigger (not less or equal) then previous-timestamp.
  • I inspect the return value of nvEncEncodePicture and consider the call successful if the value is either one of NV_ENC_SUCCESS or NV_ENC_ERR_NEED_MORE_INPUT
  • If the value is NV_ENC_SUCCESS, then I consider that I have an output encoded frame. I maintain a queue with what was passed to the encoder, and in what order. It is a FIFO basically. I take the oldest NV_ENC_OUTPUT_PTR, lock it, extract te bits stream and timestamp, unlock it
  • The problem
    All the above works as expected, except on sporadic occasions where I get the timestamps messed up. Here is a real log dump:
    On input I feed in the following timestamps:


    On output I get:

    37037682351 <<<<<BANG!!!!

    Notice how 37037670351 and 37037676351 were skipped.

    Any hints on what might go wrong?

    Best regards,

    Hi Andrei,

    Have you enabled lookahead NV_ENC_RC_PARAMS:: enableLookahead? If yes, can you try disabling lookahead if you see the same problem?

    Secondly, are all NvEncEncodePicture() calls returning NV_ENC_SUCCESS or NV_ENC_ERR_NEED_MORE_INPUT? OR are you getting any other return values from NvEncEncodePicture().

    Ryan Park

    Hi Ryan,

    Thanks for getting into this issue. Will test the disabled LA and come back with the results. As for the return values, no, I do not get any other return values. Only those 2