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H.264 encoder latency questions (catalog implementation)

Tim Sloper
Intellectual 1750 points

Support,

Can you address the following customer question regarding our H.264 encoder (non-proprietary implementation)?

We’re trying to come up with some numbers as to end-to-end latency.  We’ve got a requirement to only have N amount of latency, where N is a number of milliseconds.  Back when you folks demo’d the 8168EVM (I think it was sometime last November, before you were on the account) I had asked what latency (in frames) the H.264 encoder had.  That is to say, once a frame from the camera is sent to the encoder, how long (in frames) does it take to come out the back end of the encoder.  To the best of my recollection the answer given at that time was 2 frames.  Is this still a correct assumption?

 

Also, is it possible to have the H.264 encoder just encode I-frames?  If so then wouldn’t the latency be reduced to just one frame?

Thank you,

Tim

  • 0
    TI__Genius 14000 points

    Hi Tim,
    The latency of the H.264 encoder on DM8168 is one frame (while being operated in FRAME mode). It means that the encoder can provide the stream of frame N, after 1 frame processing time (33 ms for a 1080P frame on a device having 266 MHZ HDVICP2).
    So on DM8168 (HDVICP @ 533 MHz) the latency is 16 ms for a 1920x1080 frame.

    The above explaination is applicable when B frames are not used.
    If B frames are used then it will add additional delay equal to the K frame processing time; where K = Number of B frames in subGOP (IBBPBBPBBP gop structure has number of B frames = 2)

    Please also note that the encoder allows to operate at sub frame level - for that situation 33 ms delay can come down to the range of ~2 ms.

    Encoder also allows only I frame encoding - but it will not help to reduce any delay compared to IPPPPP gop structure.

    Thanks,
    With Regards,
    Pramod