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  • GMP JCs insertion

    From Shishir@21:1/5 to All on Wed Jul 17 07:49:43 2019
    Hi,

    Q: If the JCs(basically Cm(t)) inserted in a OPU4 frame , is for next frame ?

    -If yes then what is the value of JCs , for first frame ?

    -If No, then how synchronization will happen at GMP sink?

    PLease confirm understanding:

    As explained in ITU TG 709 - Annex D:

    "Before GMP Sink synchronization: incoming II/DI values are indication that GMP source may change Cm(t) values in next frame. This seems II/DI field of current frame is telling about Cm(t) of next frame.

    Though after GMP sink synchronization: Spec says to use II/DI along with current Cm(t) to demap payload."

    IS that the case, as if behavior of II/DI changes before(used to decode Cm(t) of next frame) and after(To decode Cm(t) of current frame) synchronization at sink side? if yes, how can this be reflected from source?

    Thanks
    Shishir

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  • From Huub van Helvoort@21:1/5 to You on Sun Aug 4 13:21:13 2019
    Hello Shishir,

    You wrote:

    Q: If the JCs(basically Cm(t)) inserted in a OPU4 frame , is for next frame ?

    -If yes then what is the value of JCs , for first frame ?

    The value does not matter because the first frame transported does not
    contain client data.

    As explained in ITU TG 709 - Annex D:

    "Before GMP Sink synchronization: incoming II/DI values are indication that GMP source may change Cm(t) values in next frame. This seems II/DI field of current frame is telling about Cm(t) of next frame.

    Yes, it is telling that it will change, not what the value will be.

    Though after GMP sink synchronization: Spec says to use II/DI along with current Cm(t) to demap payload."

    Correct.

    IS that the case, as if behavior of II/DI changes before (used to decode Cm(t) of next frame) and after (To decode Cm(t) of current frame) synchronization at sink side?

    If II/DI procedure is followed as described sink side and source side
    are synchronised.

    Kind regards, Huub.


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