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Video card specs for HDMI input

Jian Tay
Intellectual 260 points
Other Parts Discussed in Thread: DLPC300

I'm trying to use the LCr to display several thousand images, as fast as possible. As of the 2.0.1 update, I see that there is an option for using the HDMI input mode to re-interpret a 24-bit HDMI signal as 24 1-bit images, thus improving the frame rate. My current video card (GeForce GT520) only supports 8-, 16-, and 32- bits-per-pixel (bbp) color palette. Does the video card specifically need to support 24-bit color or can I use the 32-bbp mode? Also, how does the output trigger look like when in HDMI mode? Will it give a 60 Hz signal or 24 * 60 Hz?

Thanks!

  • 0 in reply to Jian Tay
    TI__Genius 9935 points

    Jian Tay,

    If you have not already done so, please have a look at this document:

    http://www.ti.com/lit/ug/dlpu004a/dlpu004a.pdf  DLPC300 Programmer’s Guide Section 2.3 and following.

  • 0 in reply to Pascal DLP
    Intellectual 260 points

    Thank you Pascal.

    I have read the document, and yes it answers my question about the trigger. However, it doesn't discuss what happens when greater than 24-bit RGB is used. As mentioned above, the video card only supports a color depth of 8-, 16- and 32-bits-per-pixel. Through my own testing, a 32 bbp setting seems to work like a 24 bbp sequence. Can you confirm that this is correct?

    Thanks

  • 0 in reply to Jian Tay
    TI__Genius 9935 points

    Jian Tay,

    I believe that this is correct, though I am not completely certain. I believe that 32 bit color is 24 bit RGB and 8 bit alpha (opacity or transparency). So, for the LightCrafter, 32 bit color should be identical to 24 bit RGB. It just ignores the upper 8 bit alpha channel.

  • 0 in reply to Pascal DLP
    Intellectual 260 points

    Ok, thanks. So far it seems to work, except that I've noticed a secondary issue. 

    I've been testing the DMD with two graphics cards, on two different computers: the EVGA Geforce 210 and the Gainward GeForce GT 520. With the EVGA 210, we've noticed that when a black pattern (RGB = [0,0,0]) is displayed, the DMD does not go completely dark - the led seems to blink on every refresh for about 600 us. However, when we use the GeForce 520, we don't have this issue and the screen looks completely dark. The settings for the LCr is exactly the same (HDMI input, 1-bit, blue led), and as far as I can tell, the video card settings are also identical except that the EVGA card reports a refresh rate of 59 Hz, while the GeForce shows 60 Hz.

    There seems to be no way to set the EVGA card to 60 Hz. I was wondering whether the refresh rate really matters, and what other settings I should choose to fix this issue?

    Thanks!

    [Edit: Never mind. Updating the drivers for the video card seems to have fixed the problem. Who would've guessed?]