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Re: DGA and tearing effects
Out of interest what method are you using to wait for the vblank in DGA? To vsync properly in DGA I have been having to perform a page flip (asking for it to be done next retrace), then waiting for this operation to complete; XDGASetViewport(Xdisplay, Xscreen, 0, Xdga.db * Xdga.height, XDGAFlipRetrace); while (XDGAGetViewportStatus(Xdisplay, Xscreen)); Would like to compare various methods to see if this is the way to go... Note that Xdga.db toggles between "0" and "1" every frame flip, to enable proper page flipping, as we always copy to the hidden page, then use the above code to flip and wait. Thanks, James On Sun, 28 Nov 2004 13:21:18 +0800 "Eugene Farinas" <[EMAIL PROTECTED]> wrote: > Thanks for your help guys! I've managed to remove the tearing on our DGA > program but the consequence is that the rendering speed went from a max of 15 > fps (w/o vsync) to 9 fps (w/ vsync). Initially, the image reading from the > camera and the copying to the framebuffer was in a single thread (w/c was > still displaying tearing artifacts even with vsync), but now I've separated > them into two threads, one thread reads the image from the camera, and the > other writes to the framebuffer. The read thread reads the image from the > camera, does some image manipulation on the image (converts 8-bit image to > 16-bit), and copies the image on a temporary buffer. The write thread copies > the temporary buffer to the framebuffer by using memcpy. My task now is to > move up the fps to a respectable 13 to 14 fps max. > > > Eugene M. Fariñas > Design Engineer, > Eazix, Inc. > B.S. Applied Physics, > UPLB > -Original Message- > From: Mark Vojkovich [mailto:[EMAIL PROTECTED] > Sent: Sunday, November 28, 2004 6:23 AM > To: [EMAIL PROTECTED] > Subject: Re: DGA and tearing effects > > On Sat, 27 Nov 2004, James Wright wrote: > > >My understanding is that flat panels do not "scan" a screen as a CRT > > does, so there is no vertcial blank period to perform a page flip. They do > > have a refresh rate of usually around 60Hz, but his is simply how aften the > > pixels are able to switch states, or how often the display is refreshed > > from the panels backbuffer. In a DGA mode if you try waiting for a vblank > > with a flat panel, then the page flip is performed immediately, instead of > > waiting for anything. The panels own circuits decide when to change the > > display anyway, so anything you try to do yourself is moot. If I am > > incorrect, then I apologise... > > > > > That's sortof the correct idea for when using the panel's VGA > interface. For the VGA interface, the panel is not necessarily > refreshing at the rate coming through the VGA connector. For DVI, > the panel is refreshing at the rate coming through the DVI connector, > but this doesn't necessarily correspond to the timings programmed > in the VGA registers. At least on the hardware I've worked on, > the VGA timing merely correspond to the input to the flat panel > scaler in the graphics chip, not the output going to the panel. > > > Mark. > > > > > > > On Sat, 27 Nov 2004 13:37:01 -0500 > > Michel Dänzer <[EMAIL PROTECTED]> wrote: > > > > > On Sat, 2004-11-27 at 16:40 +, James Wright wrote: > > > >About a year ago I was using DGA for my games graphics library. I > > > > was told by various people that using DGA was not the way to go. At > > > > first I thought this was nonsense, as you can't get vsync using the > > > > more standard XPutImage method (and get tearing). However, all changed > > > > when I bought a laptop with TFT screen. Problem is, there is no vsync > > > > on the new LCD/TFT monitors! > > > > > > There is in my experience, at least if you use the panel's native mode. > > > > > > > > > -- > > > Earthling Michel Dänzer | Debian (powerpc), X and DRI developer > > > Libre software enthusiast| http://svcs.affero.net/rm.php?r=daenzer > > > > > > ___ > > > Devel mailing list > > > [EMAIL PROTECTED] > > > http://XFree86.Org/mailman/listinfo/devel > > > > > > > ___ > > Devel mailing list > > [EMAIL PROTECTED] > > http://XFree86.Org/mailman/listinfo/devel > > > > ___ > Devel mailing list > [EMAIL PROTECTED] > http://XFree86.Org/mailman/listinfo/devel > > --- > Incoming mail is certified Virus Free. > Checked by AVG anti-virus system (http://www.grisoft.com). > Version: 6.0.797 / Virus Database: 541 - Release Date: 11/15/2004 > > > --- > Outgoing mail is certified Virus Free. > Checked by AVG anti-virus system (http://www.grisoft.com). > Version: 6.0.797 / Virus Database: 541 - Release Date: 11/15/2004 > > > ___ > Devel mailing list > [EMAIL PROTECTED] > http://XFree86.Org/mailman/listinfo/devel >
Re: DGA and tearing effects
On Sun, 28 Nov 2004 [EMAIL PROTECTED] wrote: > The problem with this is my project targets older laptops, it's a engine > management system tuning suite and alot of these car guys have junk bin > laptops sitting in their cars (pentium class) with a wide array of graphic > chipsets and displays. I don't think anyone will be using a accelerated > glx system, won't find any nvidia's here. I chose VESA because it seems > to be the easiest way to get higher than vga resolutions reliably on > the target hardware... going this route tosses acceleration capabilities > out the window hence the strive to use direct framebuffer rendering (at > least when linear framebuffer is available). > > It may be passe, but it's the fastest method (and oh so beautiful) I've > managed > to wring out of my p133 development workstation. > > Does this glx method provide great results even on Xvesa non-nvidia > systems? I don't have a good survey of OpenGL implementations. You might ask one of the DRI or Mesa-related lists if vsynced buffers swaps are very common, or still rare. And also, what kind of glDrawPixels performance they get. I would guess not much attention has been paid to old pre-AGP machines such as yours though, so maybe OpenGL is not such a great solution for such old hardware. Mark. > > Also, I was not aware that the flat panels had this vertical retrace > issue... one of my test machines has a 18" flat panel and it was tearing > like crazy when I just did a vga_waitretrace() before doing the page > flip. However it should be noted, that after switching to Abrashes > method of polling the display enable bit before performing the flip and > then waiting for retrace has eliminated all tearing on the flat panel > display... this was tested in 640x480 800x600 1024x768 and 1280x1024 > the native resolution of the panel. It has however, caused some tearing on > my 133 w/matrox on a CRT where before there was none... this I suspect > is a matroxism though. > > Thanks for the replies, this thread has been prettty informative thus > far. > > Cheers. > > On Sat, Nov 27, 2004 at 01:56:44PM -0800, Mark Vojkovich wrote: > >In my opinion, direct framebuffer rendering is passe. My > > recommendation is to render into system memory, use glDrawPixels > > to copy to a GLXDrawable's back buffer and then use glXSwapBuffers > > to display the buffer. At least with NVIDIA's binary drivers > > this should be faster than direct framebuffer rendering because > > rendering to system memory is cached, and glDrawPixels uses DMA, > > and if the __GL_SYNC_TO_VBLANK environment variable is set, > > glXSwapBuffers will sync to vblank regardless of whether you > > are rendering to full screen or a smaller window. > > > >This would be the most portable method, and I would hope > > all OpenGL implementations have a way to do vblank-synced > > swaps by now. > > > > Mark. > > > > On Sat, 27 Nov 2004 [EMAIL PROTECTED] wrote: > > > > > Is XFree86 w/DGA the only way to achieve high performance direct > > > framebuffer rendering (page flipped) without any negative artifacts on > > > linux? > > > > > > I'm using svgalib w/vesa right now for a strictly 8bpp project and the > > > only way I've managed to get fast (full) frame rates without tearing or > > > flickering is page flipping when linear frame buffer is supported. > > > However, it took some vga hacks to reliably sync before the flip (just > > > waiting for retrace doesnt work, I duplicated the Abrash-documented method > > > reading the vga status port and waiting til it is mid-scan (display > > > enable) > > > to set the start address then waiting for retrace to ensure the new offset > > > gets a draw in). > > > > > > It's working fine on all my test machines which it would tear on before I > > > implemented the Abrash method (previously I just waited for vertical > > > retrace then flipped the page), but now it tears on the only box the old > > > approach worked flawlessly on :( It looks like my matrox millenium II > > > notices when you change the display start address mid-scan and > > > demonstrates this with a regular (every frame) tear. My Abrash books say > > > to set the address while the display is enabled as it's supposed to have > > > latched onto the last start address for the duration of the scan... grr. > > > > > > Any suggestions would be much appreciated, I know this is a bit of a > > > thread-hijack but it's somewhat related to Eugene's question. I've been > > > considering going down the DGA route and adding X to the mix due to > > > the problems I've been encountering... I'm just not sure it will solve > > > all the problems, and will probably add new ones. > > > > > > Thanks in advance for any input, I'm sure many of you have had to deal > > > with similar issues. > > > > > > > > > On Thu, Nov 25, 2004 at 11:38:17AM -0800, Mark Vojkovich wrote: > > > >If you want tearless rendering you should be
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