[PD] Approaches to "show control" platforms

Antoine Villeret antoine.villeret at gmail.com
Mon Nov 17 10:58:10 CET 2014

regarding benchmarking between Pd and Max, I tried the two to do real time
video mapping and Gem was faster and easier to customized to reach best
for example, with Max and an IIDC camera you can't easily use the
non-standard image format and get more than 60fps. This is easily possible
in Pd.
and concerning the OS, on the same machine (Macpro 2011), the same Pd patch
run approximately 20% faster on Ubuntu than on Mac OS.
also, the screen refresh rate is not easy to tweak and AFAIR you can't
disable vertical sync on OS X.

do it yourself

2014-11-17 10:24 GMT+01:00 Simon Wise <simonzwise at gmail.com>:

> On 17/11/14 17:57, Stephen Lucas wrote:
>> We've been very interested in implementing a custom show runner with a
>> focus on making cues for reliable routing of multichannel audio and
>> multichannel video. I built a player in Max6 to get 3ch video 2ch audio
>> for
>> somebody's show and it ran pretty well. However, when trying to implement
>> the same code for a piece that relied on having very consistent, very
>> smooth HD video, we couldn't maintain a consistent framerate. Ultimately,
>> we used QLab, but we'd prefer to not need their expensive licenses.
>> I'd be interested to know benchmarks for multichannel audio and HD video
>> playback using Pd/GEM. We hadn't investigated it since I assumed Jitter
>> rendering to GPU with HAP should be better than what GEM can do, but I
>> would be ecstatic to go to Pd for this if the playback performance was
>> good.
> Video playback is very hardware dependent, GEM uses openGL so what you can
> output depends on the GPU, the drivers for this, and the speed of your
> media drives and the speed of the available transfer to the GPU.
> Depending on the cueing and sync requirements it can be much easier to run
> 1 smaller computer for each video output, but for very tight sync a single
> computer may be better.
> I have been using Raspberry Pis recently to run multiple projection
> screens, at $40 or so each they can deliver 1 HDMI output with stereo HDMI
> audio, at 1024p resolution and can be be cued via ethernet using a pd
> patch. Some other machine could run as many audio channels as you want, and
> the cues. Audio channels are limited by your audio hardware/budget.
> Raspberries not the easiest path, GEM is not much use (yet?) since they
> use openGL-ES, and really this is about the limit of their capabilities and
> will need careful tuning for good performance. I put together an external
> for pd that will load a media file in a paused state, then play it very
> tightly on a cue using DBUS, I used it last week and I'm in the process of
> cleaning it up to share. I achieved projection mapping and some alpha
> overlays on an earlier version of the show, but ran into the GPU limits as
> far as resolution and such was concerned and fell back on this approach.
> The same idea is much much more easily achieved using more powerful (and
> expensive) devices, and GEM.
> For many years I have been using old mac minis as the playback units,
> using one for master timing and audio playback it is easy to use a metro to
> play each machine frame by frame and keep video-frame-accurate playback and
> cues across as many projectors as you have minis. The first time I did this
> was 8 years ago, with a 5 projector installation making a single very wide
> HD image of a dancer moving across the whole field so frame accuracy and
> audio sync was very critical. All the capabilities in GEM are of course
> available for mapping, effects and such. You will want a dedicated ethernet
> switch for the LAN so nothing interferes with the communications. Even G4
> mac minis can deliver multiple audio channels and multiple video layers,
> this is well within the capabilities of reasonably priced machines today.
> Another approach depends on a single powerful machine. Using technology
> available in 2007 (but not cheaply!) I used a PCI based industrial video
> grabber card which could deliver 4 composite video streams (selected in pd
> from its 16 composite inputs) to the GPU without much CPU use at all, then
> with SATA drives I could add HD media playback ... I gave up testing at 12
> alpha layers with mapping (some HD, some camera, some generated scrolling
> text etc with fades and playback all completely smooth). It was all
> achieved in pd with the user interface entirely via a midi fader board. I
> had set this linux box up because I was projecting live camera images
> behind the actors speaking and needed close to lip-sync with the performer
> ... the only possible way was a PCI frame grabber like this, the cameras
> were old and not gen-locked but the delay was always between 1/2 and 1 1/2
> frames so it worked out fine. Firewire or any other transport was useless
> since there was too much buffering hence unusable latency.
> Graphics cards are much more powerful now, though getting that kind of
> connection into a machine and directly to the GPU will take a careful
> selection of motherboards. The machine was also used at other times to run
> 4 DVI outputs (it had 2 linked Nvidia cards) from this vision mixer, it
> toured through many venues in the hands of a non-computer, very much
> analogue video guy without any need for my intervention ... it was all
> extremely stable and comfortable for traditionally trained theatre techs to
> handle.
> Simon
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