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How to get the correct input frame rate with DM6431?

Eric Fang
Intellectual 485 points

Dear Sir,

When I use 6437EVM board, I can get a 30 frames per second frame rate.

But when I port my project to DM6431, the frame rate becomes 15 f/s.

I know the DSP clock change from 594MHz to 297MHz.

Therefore, I change the "vpss_div" vaviable from 11 to 5 in the gel file.

But I still get the 15 f/s frame rate.

What should I do to get the 30 f/s frame rate?

 

Best Regards,

 

Eric Fang

   

 

  • 0
    Genius 3575 points

    Remember, there are 2 independent plls on the dm643x family.  Even though you are limited to 297 MHz with pll1, I'm pretty sure you can keep your pll2 outputs that control the ddr2 the same.  That being said, the vpss_div variable in the gel file is used for the dac output, which does not exist on the dm6431.  Are you doing any data processing?  Because your DDR2 bandwidth is cut in half when you change from the 6437 (32 bit DDR2) to the 6431 (16 bit DDR2).  So if you were compute bound before, you are now operating at 1/2 the frequency, so you should expect 1/2 the bandwidth.  And if you were data throughput bound, well you now have half the data bandwidth.

  • 0
    TI__Mastermind 41665 points

    I think Matt is on to this one, with the DM6431 if you had any sort of performance saturation (using all the DDR bandwidth or using all the CPU bandwidth) with the DM6437 than you could expect about half of the performance with the DM6431.

    Since the DM6431 is an input only device (just a video capture port) I am curious how you are measuring the frame rate? If you are measuring on the capture interface than are you seeing half the clock rate or half the vertical sync rate? I am trying to understand where you are seeing half the rate if this is not just a performance issue.