Page 2 of 2 FirstFirst 12
Results 11 to 18 of 18

Thread: Raspberry Pi

  1. #11
    Join Date
    Oct 2009
    Location
    Eindhoven, The Netherlands
    Posts
    921

    Default

    Quote Originally Posted by drlava View Post
    The 'really cool stuff' that you're talking about is already possible inexpensively with LSX laser show software, you should really check it out some time. With this you can use with the Etherdream or any DAC of your choosing. There are advantages to having the processing engine on the computer, that, while at first it may seem like a good idea to have it on the DAC....
    One of the problems with having a 'dumb' DAC (worst case: a sound card) depending on a host system is performance. Especially when your host is running a poorly programmed operating system with a dodgy driver model (e.g. Windows), you may very well run into some timing issues, or even crashes.

    When you have the Raspberry Pi on board the projector, the DAC *is* the host system. Think of it as having multiple computers with their own instance of your favorite laser show package running simultaneously, one in each projector. They're not dependent on each other or on a specific host to get their frame data, only on the network for synchronizing them together and for interfacing with the laserist.

    I'm not saying you should get rid of the host system at the front of house altogether and have some dumb terminal at that end, on the contrary -- I only suggest moving the frame generation logic to where it is needed most (the projectors), freeing up more processing power on your host for things like new user interfaces and really processor intensive stuff that is not timing critical (as opposed to the frame generators, which need to be fairly real-time), like modeling or rendering in 3D, processing video and other complex operations. When that's done, a new bunch of vector data can be streamed to the projectors which can use them on demand.

    The only thing the DACs have to do is crunch a bunch of points (sets of X, Y coordinates), which is an operation that can be done on that ARM 700MHz processor at a rate of millions per second. So I doubt we're going to run out of processing power to do complex frame transforms there in the future.

    Just for the sake of comparison, how much processing power is there on high end boards like the QM2000.NET or Lasergraph? Judging by the specs, the Raspberry Pi could run rings around those boards.

  2. #12
    Join Date
    Apr 2010
    Location
    USA
    Posts
    216

    Default

    The argument for super-intelligent, Linux-based network DACs is well-founded - a Raspberry Pi or Beaglebone is more powerful than the desktop PC that a QM2000 might have been put into around when it was released, which means that math and effects that would have been state of the art back then can run handily on a modern ARM.

    The counterargument, though, is that PCs have sped up an awful lot too. Effects that a Rasperry Pi would have its hands full with are basically epsilon on a modern CPU/GPU combination, and processing things all the way down to a raw point stream on the PC makes engineering the whole system a lot easier. The network protocol is just "here are some points", not "here's a bunch of backing data; now do your translations on it". (GPUs require large amounts of bandwidth to the host memory. If you replace the ultra-low-latency 64 Gbit/sec PCIe link between a modern GPU and its host system with Gigabit Ethernet, it won't work quite so well...)

    There's also an upgradability issue - see the troubles people have had looking for hard-to-find old DIMMs to upgrade the memory on a QM2000. Buying a new, faster PC isn't a big deal - the engineering effort on computers is amortized across basically the entire world, as opposed to our little laser niche. Modern OS kernels are pretty good at real-time handling, and in any case, moving the real-time code to a "big" embedded system doesn't solve all problems magically either. These boards just runs Linux, after all, a grown-up desktop-oriented OS like any other.

  3. #13
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
    Join Date
    May 2007
    Location
    A lab with some dripping water on the floor.
    Posts
    9,890

    Default

    Run rings around a Quad Transputer with Mathcos, maybe not?. (Lasergraph DSP)

    QM2000 is a Coldfire with a novel fast DRAM accessing scheme that was so unique 'Rola let Bill Benner post it as a Motorola applications note world wide. BB has authorship credit on a AP note, and that is a rare thing for a outsider.

    I think Mr Pi only has pure speed over a Coldfire.

    On the other hand, look what some very clever code lets a Coldfire do, pretty much independent of its host.

    QM32 was a 40 Mhz 68040, and my QM32 has continued playing shows when the Host 98 or ME system has crashed BSOD.
    QM32 was famous for doing that, the PC was just a user interface, power supply, and storage.

    Only with " Beyond" has the QM2000 become pretty much a "DAC", before that the 2000 did perhaps 90% of the work if you ask Mr Benner.

    Whats amazing is how little firmware space is used on a Pangolin product. My QM32 has two 64K eproms if I remember correctly, I'm away from home so I cannot go check.

    So what does the 700 Mhz Tiny ARM really have, other then pure speed, gained from Moore's law?

    You could probably almost "emulate" the Coldfire on the Pi. However, the real magic is in the years of time spent writing the code that does a laser show with such precise timing and repeatability, and functionality. Without that code even a state of the art board like Pi is a mere paperweight.

    I have a board that plays laser images on a 4 Mhz Z80, its not the processor, its the man hours of code that is unique. A playback frame dumper is easy, I can do that with simple counters, sram or eprom, and glue logic, the real magic (tm) is in the system code.
    Since the only freeware code is LFI, even if you get a Pi, what are you going to run on it?

    Steve
    Last edited by mixedgas; 12-30-2011 at 22:49.

  4. #14
    Join Date
    Aug 2008
    Location
    UK
    Posts
    5,704

    Default

    Quote Originally Posted by j4cbo View Post
    There's also an upgradability issue - see the troubles people have had looking for hard-to-find old DIMMs to upgrade the memory on a QM2000.
    I believe the hardware has recently been upgraded on the newer QM's to try to alleviate that problem going forward. For existing QM owners, I noticed on their web site that you can buy DIMM's from Pangolin although whether they have any stock I'm not sure.

  5. #15
    Join Date
    Oct 2009
    Location
    Eindhoven, The Netherlands
    Posts
    921

    Default

    Quote Originally Posted by mixedgas View Post
    You could probably almost "emulate" the Coldfire on the Pi. However, the real magic is in the years of time spent writing the code that does a laser show with such precise timing and repeatability, and functionality. Without that code even a state of the art board like Pi is a mere paperweight.
    Oh, I will defnitely have to agree with that! I'm all for developing a completely new platform based on the Pi (or any other ARM board running Linux), together with a desktop host running Linux, since it opens up a lot more possibilities. Sure, you can use the Pi as a 'dumb' DAC if you want and if you don't need anything more, so the integration with existing systems is fairly seamless. But if you want to do additional features on the DAC, that's perfectly possible because you have plenty of processing power left.

    I can also see it moving from the realm of 'players and displayers' into the realm of modular software synthesizers where you can define an arbitrary rendering graph for every projector or even build/change it on demand at show time. So if you have a show that's being played back from a linear time line, it'll just play straightforward, but if you want to intervene by adding live frames, manipulating parameters or adding abstracts, you could add filters for that on the fly.

    The FOSS community needs to get off their bum and start writing software for us laserists.

  6. #16
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
    Join Date
    May 2007
    Location
    A lab with some dripping water on the floor.
    Posts
    9,890

    Default

    The FOSS community needs to get off their bum and start writing software for us laserists. [/QUOTE]

    The guys who have done it have been so abused by needless complaints that they all have quit.
    Laser show software is a demanding real time application. Real time control on a Windows platform requires programmers that know hardware, are demented, dedicated, and special. Thats rare.

    Steve

  7. #17
    Join Date
    Oct 2009
    Location
    Eindhoven, The Netherlands
    Posts
    921

    Default

    Quote Originally Posted by mixedgas View Post
    The guys who have done it have been so abused by needless complaints that they all have quit.
    Laser show software is a demanding real time application. Real time control on a Windows platform requires programmers that know hardware, are demented, dedicated, and special. Thats rare.
    Steve
    The FOSS developers I know don't even worry about complaints from mere users. (We're too busy developing, not tech support), and most of the FOSS stuff that's in the real time realm is in permanent alpha or beta stage until there's enough backup from other developers to provide support to people who need it.

    Most of the building blocks that are needed have already been built. For example, if you use a package like Pureata together with JACK, you can run a live laser show without any additional coding, but there's the drawback of not having an intuitive interface.

    At the very least I'd like to take a top-down look at the laser display infrastructure: What do we as laserists need or want in terms of user interface, creative opportunities and hardware features, instead of developing bottom up through improving on the existing "DAC/tape-player with a projector attached" concept.

  8. #18
    Join Date
    Jul 2010
    Location
    Netherlands
    Posts
    3,314

    Default

    The Raspberry Pi sounds so good
    Especially for development, also in doing some 3D calculations for say safety which might help if your using one of those not good intergrated video card laptops (which are of a low vertex and pixel shader version).

    The only thing i'm wondering is where to attach a DMX in and out and the ilda itself to

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •