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"internal" and "external" frame rate?

Merab Avto
Prodigy 100 points

Which are internal patterns and which are external?

I need to project binary frames as fast as possible, and then the difference between the internal frame rate (4000 Hz) and external  (1440 Hz? (60Hz * 24)) is large.

Is the internal mode only when all of your frames are preloaded into the builtin RAM? If no,how else can I play frames in internal mode? If yes, does that mean even at lowest resolution I can only play few seconds of video at 4000 Hz? (4000 * 1 * 320 * 240 bits for each second)?

Any way some of the old frames can be removed from the RAM and new ones loaded while the animation is playing to not be limited to few seconds, yet still not drop to 1440 Hz (external mode)?

And can the RAM be upgraded by the user?

  • 0
    TI__Genius 11345 points
    Hi Merab,

    Yes, there is a difference between the external and internal pattern rate as you mentioned on the LightCrafter. The internal patterns can be displayed at higher rates, since all of the patterns are pre-loaded in to the rotating buffer that resides in the mDDR.

    For 1-bit patterns, you can store up to 96 patterns and achieve a pattern rate of 4000 Hz. The architecture of the system does not allow for changing the size of the rotating buffer used.

    Could you describe your use case more? What is your application? How many total patterns do you need to display? What is the bit-depth of these patterns? Any other requirements for your use case?

    Thanks,
    Clinton
  • 0 in reply to Clinton Rodgers
    Prodigy 100 points

    Thank you for the response. My project is a volumetric display similar to this one: gl.ict.usc.edu/.../3ddisplay
    This is a 3d display based on high-speed projection of 2d "slices" on a rotating screen. The number of frames each second is equal to slice_count * frame_rate_for_each_slice.
    With the external framerate speed the Lightcrafter allows for example 120 slices at 12 fps. however, I am not sure if that is fast enough for our persistence of vision to still work and also not introduce large amount of flicker, or whether 120 slices vs 180 is enough to produce a uniform 3d volume. At 4000 fps I can get 166 slices at 24 fps per slice which is closer to what others have used.
    Since 3 Lightcrafters is needed to achieve dithered RGB videos, my budget won't allow to get the much expensiver Lightcrafters and I can't find an option (both from Texas Instruments and 3rd parties) to purchase just the control board without the light engine/etc for $700 or less each with faster external refresh rate.

  • 0
    Prodigy 100 points

    Wait, after reading the manual some more, it seems "external mode" means frames preloaded in to the SDRAM? Does that mean I'm limited to 128 MB then?
    This is so misleading. In the GUI program the external pattern settings are under the HDMI menu so I thought I could stream frames via the HDMI in "external pattern mode". Or did I get it wrong?
    It seems via the Ethernet/USB/HDMI I can only do 60 Hz which makes this Lightcrafter no good.

    Is there another product in this price range Texas Instruments or 3rd parties provides for projection >1000 Hz binary frames from a memory card or HDMi/DVI/USB?
    I dont need the light engine or even a DMD. Just a DMD controller board will do. I have only found expensive kits with everything included but beyond my budget.

  • 0 in reply to Merab Avto
    TI__Genius 11345 points
    Hi Merab,

    I believe you are looking at the 'extended' pattern sequences section of the LightCrafter user's guide, which follows the 'external' pattern sequences section. For external sequences, using 1-bit patterns, you can stream in patterns at 1440 Hz using the mini-HDMI port (DVI-D compliant).

    When you say "2d slices" above, do you mean 1-bit patterns?

    Thanks,
    Clinton