Le 17/07/2012 21:36, Cyrille Henry a écrit : > hello, > > osX synchronize openGL rendering to the screen. i.e if your external > screen is at 59.9 fps, Gem will not be able to render more than 59.9 fps. > since Gem rendering is connected to pd timing, it is connected to > audio processing. i;e : if gem is only able to compute 59.9 fps when > 60 is asked, then pd time will not be synchronize with real world > time. so you have click on the sound. > > (desincronize openGL render to screen is usually not an option, since > result are ugly with fast moving images) > > moreover, Gem rendering are computed during pd data processing, i.e. > between every audio block. by default, pd use 64 sample buffer. so pd > compute audio buffer every 1.5ms. You have to expect a bit of jitter > on the 16.666ms needed between 2 images rendered, accentuating > previous effect. (if gem image is rendered 17ms after the previous, > one have to wait an extra 16 ms...) > > Using faster computer will not solve this problem. using faster screen > will offer a solution, but that's not a good solution for me, and > probably not for you. > > If you really need frame accurate render, easiest solution is to > desynchronizes sound and image processing. pd~ is not an option since > the 2 process will have the same timer. > So, you have to use 2 pd, one for the sound, one for the image, > synchronised using netsend / netreceive (on localhost). The best is > probably to ask 100fps to Gem, so that it will sync to the screen > frequency, whatever the screen is). Then, you should use the screen > frequency as the time base of your performance. Hello Cyrille,
If you have Gem at 100 fps and you screen at 60 fps, you should encounter a problem of sync at a certain moment, no ? If not, can you explain more ? Maybe the best is when you have Gem fps as a multiple of your screen fps ? Thanx for the rest of explanation. ++ Jack > > using this solution is not to hard to have sound synchronize on screen > rendering. > hope that help, don't hesitate to ask more precision if i'm not clear. > > Cyrille > > > > Le 16/07/2012 19:31, Theo Burt a écrit : >> Hi, me and a friend of mine do a lot of live audio-video performance, >> professionally, all using pd/gem as an environment. We both use >> Macbook Pros (different models), and for the last couple of years >> we've been having a serious problem which we now suspect is something >> to do with GEM/PD, rather than, for example, the graphics cards or >> drivers. >> >> The problem occurs when running at higher frame rates - it is highly >> preferable for us to run at 60 frames per second, because (1) it >> syncs with the refresh rates of most projectors and seems to produce >> much smoother/more regular movement, and (2) often we are using very >> precise, high frequency flashing, for optical effects, that we need >> to be able to sync exactly with screen refreshes. We are generally >> running the gem window in a second screen (such as a monitor or >> projector), but it happens when running on one screen too. >> >> As soon as we run at 60 frames per second (or near it), glitching >> starts to occur frequently in the audio, and the audio goes out of >> sync with GEM. While the glitching is occurring, processes in PD and >> GEM jerk along, pausing frequently. To resolve it (temporarily), the >> audio has to be reset in PD (by reselecting the audio device). The >> glitching then goes away and everything runs smoothly, but it returns >> spontaneously after a short time. The glitching is also exacerbated >> by moving windows around on the screen. It might be worth noting that >> the same patch running on the very same machine in Windows XP (using >> bootcamp) does not have this problem. >> >> We have different GPUs, mine is a Nvidia 9600m GT, and his was an ATI >> of some sort. We are using very simple, geometric graphics, and are >> not approaching the processing limits of the GPUs at all (if I do >> push the graphics card very hard, I notice that frames are skipped >> rather than glitching occurring). I also note that it happens equally >> when there is low CPU activity, so it's not related to that. >> >> My friend has just purchased a new Macbook Pro, yesterday with a 60% >> more powerful Nvidia GPU, and unfortunately the glitching is still >> occurring. It occurs in OS X Lion, and also was happening in Snow >> Leopard. We've tried disabling power management on the GPU, and this >> doesn't help either. >> >> I've looked through the gem code in an attempt to try and understand >> what is happening, but I am afraid it is beyond me! >> >> Does anyone have any idea at all what the problem could be? It would >> make such a huge difference to us if we could resolve it. Thanks very >> much for any help in advance (and for developing GEM in the first place) >> >> All the best, Theo >> >> _______________________________________________ >> GEM-dev mailing list >> GEM-dev@iem.at >> http://lists.puredata.info/listinfo/gem-dev >> > > > _______________________________________________ > GEM-dev mailing list > GEM-dev@iem.at > http://lists.puredata.info/listinfo/gem-dev _______________________________________________ GEM-dev mailing list GEM-dev@iem.at http://lists.puredata.info/listinfo/gem-dev