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The calculation of BM when using VCP2

Kaiqi Yang
Expert 1015 points

Hi, guys. I know that the BM is calculated by DSP, and I'm wondering that if the BM is calculated in advance before decoding by VCP or the BM can be calculated while do decoding by VCP at the same time?

  • 0
    TI__Mastermind 18146 points

    Hi Yang,

    as the branch metrics are an input to the VCP2 you need to calculate before sending of to the VCP2.

    But since the VCP2 is operating independently from the CPU you can calculate the BM in parallel with the VCP2. This means you can implement a pipelining scheme to continuously feed the VCP2.

    Kind regards,

    one and zero

  • 0 in reply to one and zero
    TI__Mastermind 30405 points

    Hi one and zero,

    Thanks for the response. I believe that while it may be possible to implement a pipeline as you suggested (since VCP2 does not need all the BM data at once before it can start decoding), this can cause a race condition. BM data is transferred to the VCP2 using EDMA which would be a lot faster than the rate at which the DSP (software) can write BM data to the input buffer in which case VCP2 can end up reading junk data from the BM input buffer.

    I believe its a safer strategy to calculate and store the BM data in the input buffer before decoding is started. Kindly comment if I missed something. Thanks.

    Regards

    -Nitin