Hello everyone,
A few months ago I asked a lot of questions about how to use the DLP4710EVM-LC as a PC-driven 1440 Hz display. Thanks to the help of Kyle and other TI engineers, and to forum member Guillaume Strub, and after some tinkering around, I'm happy to say that I managed to make it work, at least in some cases. This note is for the benefit of anyone else who might want to do this.
To drive the 1440 Hz 1-bit monochrome mode, you need to compress 24 frames into each image, each frame in one bitplane. (I found the documentation confusing: to display your images in correct temporal sequence, put the first frame into blue bit 0 (least-significant), then blue bit 1, ..., blue bit 7, green bit 0, ..., green bit 7, red bit 0, ..., red bit 7.)
This biggest problem is when video cards try to 'improve' your image and introduce luminance or color corrections: this screws up your bitplanes, which you need to control perfectly. Some cards have drivers that expose this 'feature' and allow you to turn it off, and just display the bits that you set (this is sometimes called "RGB pass-through") -- these are the ones that work. The simplest way to check is to fill the screen with 24 rectangles, each in one of the 24 bitplanes, and put the projector into 1440 Hz mode. If you see uniform luminance, there's a good (but not perfect) chance that your video card is leaving your video signal alone.
I managed to get RGB pass-through on two machines running Windows 7 Pro SP1 (both Dell Precision T1700s), both with NVIDIA cards: one with a Quadro K2000, the other with a Quadro K4200. Note that the driver version is important: didn't work with older 340.66 drivers, but did with 416.78. If the driver detects the projector as a TV, it will automatically compress the output range of each color channel to 16-224 or something, which will of course screw things up. You need to go to Nvidia options/Display/Change resolution and scroll down to see if you find the option "Output dynamic range"; if so, set it to "Full." If you don't see this option, probably everything will work out OK.
I also managed to get RGB pass-through on a ThinkPad X1 Yoga 2nd generation laptop (2017) on Win 10 Pro 64 bit, with a built-in Intel HD 620 graphics card (driver version 21.20.16.4727) and a built-in HDMI output port. Again, I had to update my drivers for them to expose the dynamic range option so that I could set it to "full" as for the Nvidia cards (look for "Quantization range" in driver options, set to "Full range").
I could NOT make it work on:
- a machine with an AMD/ATI card, running Windows 8
- a Dell XPS 13 laptop (model number 9950 from 2016), Win 10 Pro 64 bit, with a built-in Intel HD 520 graphics card
I haven't tested any Macs or Linux machines.
A final note on generating images by compressing frames into bitplanes. This turns out to be easy using old-school fixed-pipeline OpenGL. Here is some Python code:
# to compress the 24 frames, assuming buffer is black glEnable(GL_COLOR_LOGIC_OP) glLogicOp(GL_OR) for i in range(24): col = 3*[0] col[2 - n//8] = 1 << (n%8) glColor3ubv(col) # draw frame, don't touch the color
Thank you again to everyone who helped!
Mark
