On 07/08/2017 06:51 PM, Harry van Haaren wrote:
3. The programming language. It is a lot easier to find someone who
knows JavaScript, or at least kinda knows JavaScript enough to get
by for a small project, than it is to find someone who knows C. For
people with minimal or no prior programming experience, higher level
languages are much easier to learn.
Surely anybody somewhat proficient in JS can figure out what this (link
below) does?? Programming is programming - logical thinking. I don't
think that the C code there is "harder" than achieving the same in JS.
Keep in mind we're not asking people to do pointer-magic here - its
basic arithmetic, and calling a functions.
https://github.com/openAVproductions/openAV-Ctlra/blob/master/examples/vegas_mode/z1.c#L45
C is more difficult to learn than JavaScript. There are a lot of details
in that code that you simply don't have to think or know about with
JavaScript. To a novice developer who knows nothing about C, they'd have
to answer these questions:
> if(e->slider.id == NI_KONTROL_Z1_SLIDER_LEFT_FADER) {
What is the difference between "->" and "."?
> uint32_t iter = (int)((d->volume+0.05) * 7.f);
1. What is a uint32_t? Why should I use that instead of a different
number type?
2. What is that "(int)" doing?
3. Why is there a ".f" after the "7"?
That's just the tip of the iceberg of understanding a few lines of code.
Fully mapping controllers requires considerably more complex logic than
that.
So, I think it would make more sense to expose Ctlra to Mixxx's
existing JavaScript environment for controller mapping. There would
only need to be two capabilities added for this to work:
1. Scripts would be able to register JavaScript callback functions
that would be called when particular Ctlra events are passed to Mixxx.
2. Scripts would need to have a way to send output messages to
Ctlra. There should be a way to freeze/unfreeze the sending of
output messages so many outputs could be updated simultaneously in a
single HID packet.
I have written a proposal for how to do this with MIDI:
https://mixxx.org/wiki/doku.php/registering_midi_input_handlers_from_javascript
<https://mixxx.org/wiki/doku.php/registering_midi_input_handlers_from_javascript>
It would be great if we could create JS APIs that are almost
identical for MIDI and Ctlra.
I'm still not sold on the idea of wrapping all of Ctlra up in JS
callbacks and then exposing it to Mixxx. Its possible, but I fail to see
why this should be the holy-grail of how mappings should work. I should
probably do up a design-doc or video on how I think *eventually* the
Ctlra / Mixxx UX for mapping a controller would look: and if I can
figure out the technical parts, it will be pretty revolutionary in how
it enables novice users to create unique mappings. Punch line is to
present the functionality (multi-layered bindings) in a way that is
easily consumed by "ordinary" humans, and provide a doc + video
explaining it. Give me a few weeks - some POC Ctlra + Mixxx code first,
then onwards to the exact mapping UX.
I'm still not convinced it is possible for any point-and-click system to
fully map most controllers *in a maintainable way*. Years ago, device
specific hacks were added to Mixxx in C++ to make the XML system work
with MIDI signals for jog wheels. Someone please correct me if I am
wrong, but my understanding is that the JS engine was added to avoid the
need for such compiled-in device specific hacks. Almost all mappings
submitted for inclusion in Mixxx recently have been done mostly or
entirely in JS. Traktor has an elaborate point-and-click mapping system
and users complain how awful it is to work with (refer to
https://djworx.com/what-do-you-want-from-traktor-pro/ for example).
I have previously thought about designing a GUI that used tabs to
organize different layers of functionality. But this would break down
quickly for handling the interaction of multiple layers and create a
mess even worse than Traktor's mapping GUI. For example, consider a cue
button that uses the cue_default ControlObject normally but start_stop
while a shift button is held. You could define a layer that the
unshifted button belongs to and another layer that the shifted button
belongs to. Okay, easy enough. Now you want to make that side of the
controller able to be toggled between deck 1 & deck 3. How would you
accomplish this? With a simple layering system, you could create 4
different layers:
Deck 1 unshifted
Deck 1 shifted
Deck 3 unshifted
Deck 3 shifted
Then you'd need to copy & paste all those 4 layers for the other side of
the controller with decks 2 & 4! It would be possible to hack support
for toggling decks into Mixxx so the mapping could deal with a virtual
deck and Mixxx would maintain the state of which deck is active, but
that would only handle this specific use case. And you'd still need to
copy & paste for the left & right sides of the controller.
What if I want pushing a button to use the beatloop_activate
ControlObject when no loop is active but use reloop_toggle when a loop
is active? I'd need to create a layer for a loop being enabled and a
layer for no loop enabled, then somehow tell Mixxx to switch between
them when that state changes. Then I'd have to duplicate both those
layers for deck 1 & deck 3. Now I want pressing that button to act
differently when shift is pressed -- and act differently depending on
whether a loop is active. When shift is pressed, I want to use
reloop_toggle with no loop active and reloop_andstop with a loop active.
With a GUI layering system, I'd need layers for:
Deck 1, loop disabled, no shift
Deck 1, loop disabled, shift
Deck 1, loop enabled, no shift
Deck 1, loop enabled, shift
Deck 3, loop disabled, no shift
Deck 3, loop disabled, shift
Deck 3, loop enabled, no shift
Deck 3, loop enabled, shift
And again copy and paste for decks 2 & 4. Now there are 16 layers for
pushing this button! What if you wanted to remap it? Maintaining even
this example would be a pain, and that's just one component of the
controller. Programming an entire mapping this would would be awful.
Also consider how you could implement
https://mixxx.org/wiki/doku.php/standard_effects_mapping
for the Kontrol X1, S2, S4, and S5 with such a system. Again, you could
hack all that logic into the C++ side of Mixxx like the deck toggling
case, but then what would you do to implement something like the effects
mapping for the Pioneer DDJ-SB2:
https://mixxx.org/wiki/doku.php/pioneer_ddj-sb2#effects (particularly
the Mixxx 2.1 mapping).
This video talks about the uselessness of visual diagramming languages
like UML, and I think much of what is said about visual diagramming
languages in this applies to programming with a GUI as well:
https://www.youtube.com/watch?v=4_SvuUYQ5Fo
That said, if you have revolutionary ideas for how to design a GUI for
mapping controllers that could actually handle all the complexity above
and not be a huge pain to work with, please share. I'd love to be proven
wrong... but I think it's more likely that you'd waste time that could
be better spent making Mixxx do other cool things or writing a new
OpenAV application.
Thanks for your input again - good points raised. -Harry
On 07/06/2017 04:57 PM, Harry van Haaren wrote:
Hi All,
First of all - this is my first post to the Mixxx-devel list, so
a brief intro is in order;
I'm Harry van Haaren, developer of the OpenAV audio software,
bit of a music/tech/linux head :)
I've recently been working on improving controller support in
Linux audio land, in particular
what I call "modern USB HID" controller devices (think DJ
controllers like Akai/NI/Abletons range).
I've developed the Ctlra library as OpenAV, which provides
access to these hardware devices
on Linux. The library allows hotplug and various other
"advanced" features like accessing
screens on devices.
I'd like to integrate Ctlra into Mixxx - to provide access to
hardware currently not available
to Linux users, and also to provide hotplug support to those
controllers. I've created a blueprint
on Launchpad[1], and written an introduction on Ctlra and how I
propose to integrate it in Mixxx[2].
Finally, there is a documentation page on what Ctlra itself
achieves here[3], and the source is here[4].
If you have an interest in hotplug of controllers, controller
support or hardware on Linux,
do have a read of the wiki page and others, and I'd appreciate
your input on the ideas!
Thanks for all your efforts on Mixxx so far, onwards and upwards!
-Harry of OpenAV
[1]
https://blueprints.launchpad.net/mixxx/+spec/ctlra-controller-support
<https://blueprints.launchpad.net/mixxx/+spec/ctlra-controller-support>
[2] https://www.mixxx.org/wiki/doku.php/ctlra_support
<https://www.mixxx.org/wiki/doku.php/ctlra_support>
[3] http://openavproductions.com/doc/ctlra.html
<http://openavproductions.com/doc/ctlra.html>
[4] https://github.com/openAVproductions/openAV-ctlra
<https://github.com/openAVproductions/openAV-ctlra>
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