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VPSS M3 load increases if Video M3 is enabled

ravindra patagar
Prodigy 50 points


Hi,

I am using Netra (TI8168-GP rev 1.1). If i do 2 1080i captures and scale only, the VPSS M3 load is ~15%. If Video M3 used, the VPSS M3 load shoots up to 65% - 70%. Also, the VPSS performance degrades and i observe reduced framerates.

Can you please help me on this?

Thanks and regards,

Ravindra

  • 0
    Guru 31670 points

    Hi Ravindra,

    This behavior is possible because of the higher load on the L3/Memory bus because of which more CPU stall occurs in VPSS-M3 resulting in higher CPU load. You would have observed similar results in A8 load also.

  • 0 in reply to Renjith Thomas
    Prodigy 50 points

    Hi Renjith,

    Thanks for the response.

    Yes, the A8 load also shoots up as you mentioned. But the L3 (DDR-3) usage for this use-case is ~350Mbytes/sec read + 350Mbytes/sec write which is ~700MB/s. Theoretically DDR-3 (@ 800Mhz) can support ~6.4 GB/s of data transfer assuming 50% efficiency.

    Is there any way to confirm whether DDR bus bandwidth is the bottleneck?

    Regards,

    Ravindra

  • 0 in reply to ravindra patagar
    Guru 31670 points

    Hi Ravindra,

    I'm not 100% sure about the exact reason here. But I think that the A8 is trying to lock the L3 bus for long, because of which all the L3 masters are starving. Hence the higher load. As you add more load to DDR by enabling encode, then effect of A8 load is creating a ripple effect which result in higher loads all across the system.

  • 0 in reply to Renjith Thomas
    Prodigy 50 points

    Hi Renjith,

    I do not have any memory intensive operation running on A8. It only does OMX calls to fill and empty the video buffers and sends out encoded frames.

    Can we change the priority of DDR controller and give more priority to VPSS M3. If yes, can you help me do the same.

    Thanks,

    Ravindra

  • 0 in reply to ravindra patagar
    Guru 31670 points

    Ravindra,

    You can refer to this thread where more info is given.

    http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/307887.aspx?pi199607=1