On Sun, Jul 9, 2017 at 1:23 PM, Daniel Schürmann <dasch...@mixxx.org
<mailto:dasch...@mixxx.org>> wrote:
Hi Harry,
> At no point to I think Ctlra will *require* also using TCC. It
just so happens that they complement each other well for my use-cases.
That seams to be a good approach. If the architecture allows to put
Ctlra drivers into runtime loaded object files, it does not matter
which compiler is used and if it turns out that TCC is the best for
our needs on a platform, fine.
> That proposal looks really good. It basically means, from a Ctlra POV,
that Ctlra is plain old C code, and exposes
generic events.
No, not generic events. The Ctlra using apllications should receive
a specific event.
By "generic event", what I mean is a specific event type, with a
specific event ID. These two combined identify one specific control item
on a physical controller device. For example, a specific button (eg
Play) sends a button event when pressed / released, using this struct
for metadata:
https://github.com/openAVproductions/openAV-Ctlra/blob/master/ctlra/event.h#L63
Note that the name of the control is *not* included here for performance
reasons. Passing strings around just isn't a good idea for performance.
Ctlra provides functions to lookup the name of each event based on
type/ID. I have "generic" applications (don't care about which HW
controller is used) that provide fully labelled UIs showing all control
names - so your use-case is covered here. (If there is an issue, we can
resolve it at the Ctlra API layer, but AFAIK the API caters for the
application's requirements).
If you turn the gain Knob on a controller, the application should be
able to now that this is the Knob labeled with "Gain" grouped for
Deck A.
See above paragraph - names of events are provided, based on the labels
physically printed on the hardware.
This might be done by a generic event + a link into a manifest file,
which may also include a photo of the controller. This metada of
each event should be optimized to be translated into a OSC address,
this should be a mandatory part of Crtra. So we need a document like
this:
https://github.com/fabb/SynOSCopy/wiki
<https://github.com/fabb/SynOSCopy/wiki>
I see no value in *demanding* that Ctlra supports OSC, in the same way
that Ctlra will not demand the use of TCC. Ctlra must be a standalone
library (with only *essential* dependencies like libUSB). Any metadata
should be directly related to the physical device capabilities. Mapping
and adding semantic meaning to the controls is up to the application.
I do not wish to include images in Ctlra - it complicates things, and is
generally just un-conventional. That said, I so see value in "visually
showing" users what controls are available, and what thier labels are.
This has already been discussed, and a POC implemented:
https://github.com/openAVproductions/openAV-Ctlra/issues/7 (note to
self, I still need to cleanup and publish the branch with the POC).
I feel the scope of Ctlra should not include the "semantic meaning" of
controllers. This was discussed previously (there's one question at the
end of the LAC talk asking exactly this), and it doesn't scale well, and
only complicates things. So Ctlra will provide an Event per button
press/release, with type/ID to identify the exact physical change.
Interpreting the meaning of that event, and mapping it to application
functionality is *not* in the scope of Ctlra.
> The application can interpret those in whatever way it wants -
OSC, JS/Mixxx, or however OpenAV stuff will end up doing this. It
keeps Ctlra just generic events, and allows the application to solve
the mapping problem in its own way. That sounds logical and a good
abstraction, which is exactly what Ctlra aims for.
Yes, that is right. Today in case of midi, the user has to figure
out which midi key is doing what. With a Ctlra enabled controller
this issue should be gone. The mapping solution can for example show
the photo of the controller, and highlight the place of action.
But even without the photo, the user knows exactly how to enable a
knob LED, using the OSC name-space as address.
The human-readable string that is provided by Ctlra library API enables
the user to understand the event. For an example of the name lookup,
please see here:
https://github.com/openAVproductions/openAV-Ctlra/blob/master/examples/simple/simple.c#L51
> In order to progress this idea, I'll post code up ASAP, which makes the
generic Ctlra events available in a callback as
part of the CtlraController class. After that, the Mixxx/JS
components must be designed / worked on to fully enable Ctlra in Mixxx.
Thank you :-)
I think for the OCS Plug and Play stuff we just need to rethink the
API a bit.
I would like to do something like this
https://github.com/mixxxdj/mixxx/blob/lv2_support2/src/effects/lv2/lv2manifest.cpp
<https://github.com/mixxxdj/mixxx/blob/lv2_support2/src/effects/lv2/lv2manifest.cpp>
in Ctlra as well.
(Sorry, I am not completely though the API so this might be wrong)
As above, I'm not liking the OSC semantic meaning side of things - Ctlra
is a C library and provides events. Mapping (to OSC, or whatever) is up
to the application. Or if there is value, somebody could create a
OscApiForCtlra library - but personally I don't see that as having value
at the moment.
We need a kind of generic data point enumerator expression for every
event, which is able to discover all controller features.
Ctlra API enables this already. The ctlra_dev_info_t struct has all
names of all events, and the counts of each. In the POC implementation,
the size of the controller, and control position / size are available as
integer values in millimeters. This enables a GUI application to "mock
up" the controller, no photos / pictures involved.
Every data point should have a function for examine like
ctlra_dev_get_osc_namespace() and ctlra_dev_get_picture_location()
Will this work? Does this fit to the ctlra goals?
I feel the Ctlra API enables the events + physical device info already.
Adding OSC namespaces etc above it is not it the scope of Ctlra, nor
should it be in my opinion. (Due to not *demanding* applications use any
particular form of mapping / interpreting events). Visually enabling
controllers is achieved by providing physical layout info of the device,
instead of using a photo - a much better solution IMO.
Thoughts / opinions? -Harry
Am 09.07.2017 um 13:18 schrieb Harry van Haaren:
On Sun, Jul 9, 2017 at 11:21 AM, Daniel Schürmann
<dasch...@mixxx.org <mailto:dasch...@mixxx.org>> wrote:
Hi Harry, Hi Be,
here some comments:
IMHO arguing about If C or JS is easier will not lead us ahead
in this discussion.
Good point - apologies for the rat-hole.
> As noted above, we can take TCC off the table for Mixxx's
use case. Personally I still love it - and it has radically
changed how I think about programming in C - but perhaps its
just not a good fit for Mixxx. I can work with that.
I am afraid a mandatory TCC based Ctlra solution will prevent
it from being successful.
At no point to I think Ctlra will *require* also using TCC. It
just so happens that they complement each other well for my use-cases.
Only a solution that works nice Windows as well as on non X86
based architectures will be accepted as a new standard.
TCC supports a variety of targets; and despite no official
releases, the git repo is pretty active:
http://repo.or.cz/w/tinycc.git
For me, the key is here to be modular. Similar to LV2 each
driver Ctlra driver can be shipped with a source file and a
meta-data file which should contain a recipe to turn the
source file into a *.so or a dll. In a future advanced step,
the hosts Ctlra library code should be responsible to read the
recipe and do what it should be done to turn it into a binary.
I'm not sure what the benefit is here - i see a pretty complex
workflow, but no ultimate gain that TCC doesn't already provide.
But I said I'd drop the TCC idea and discuss other options.
> Lets find a better solution for novice / casual users who
don't want to compile anything.
The compile step itself is not the issue. If we look for
example to OpenGL Shading Language, where we also have a
compiler step no one noticed.
Good point.
>> Even if we have a ctlra controller in Mixxx, we need to
adapt the signals to Mixxx Control Objects using xml or js files.
> Why XML or JS? I see many more options, and just because we
have existing infrastructure for a similar case doesn't mean
its always the correct solution.
Just because Mixxx is using it right now. It is IMHO not in
the responds of Ctlra to convert controller events into
application commands.
OK - then lets investigate this option more. Keep in mind that my
JS experience is limited, and that I'm not particularly familiar
with QT/Mixxx's JS engine capabilities.
I'll post a PR asap that exposes Ctlra events to Mixxx, and then
see what kind of JS magic is required on top to expose that to the
JS mapping scripts.
> I'm still not convinced it is possible for any
point-and-click system to fully map most controllers **in a
maintainable way**. ...
This is should be out of scope of Ctlra.
Absolutely yes - this is outside the scope of Ctlra - at this
point we are talking about the integration of Ctlra + Mixxx in
particular. This was noted by a few developers at the LAC too,
that device access is only a part of the problem. Providing a good
mapping mechanism is the harder part. But we need step 1 (Ctlra
device access) before step 2 (easy/powerful mappings).
IDEA:
Thinking of all of this again, I think this Ctlra project is a
great chance to fix some issues, existing standards have.
* Midi: Midi is that successfully, because it is defined up to
the Application layer for a Midi-Keyboard. Reusing this for
other types of controllers works, but pushes it down to the
Presentation Layer.
* OSC: OSC fails to define the Application layer. It is
promoted to be a Midi successor, but it even has no standard
way to even transport good old midi messages. There are
approaches to fix this in some OSC namespaces, but this is
somehow stucked.
It would be grate If we could get back to the state of
original Midi Plug-And-Play behaviour for Midi-Keyboard for
all type of controllers using Ctlra. If we do this along with
a OSC namespace for Ctlra, this will be a great benefit and
probably a very successfully.
Lets see!
On a Midi-Keyborad you know exactly which phsical key is
pressed an how just looking to the midi Message.
This can be done for Ctlra as well, I we define a message like
"Gain Knob Deck A 56 %" So a new controller will be instantly
usable for Mixxx with a basic default mapping. This is
probably not sufficient, but putting a new function on "Gain
Knob Deck A" can be done by existing mapping solutions.
Yes, simple "static" mapping schemes can be easily handled by
mapping event IDs to ControlProxy objects. As Be pointed out, the
difficult point is layering multiple functionalities over each
other in a user-workable way.
I have these Architectures in mind:
OpenAV setup:
HID-Controller
V
Ctlra Driver
V
Cltra Lib
V
C Mapping
V
OpenAV App
Mixxx setup:
HID-Controller
V
Ctlra Driver
V
Cltra Lib
V
Controller Proxy
V
XML / *js mapping
V
Mixxx engine
Gnereic OSC setup:
HID-Controller
V
Ctlra Driver
V
Cltra Lib
V
OSC Wrapper (process)
V
UDP/TCP
V
OSC to OSC mapper
V
UDP/TCP
V
OSC enabled DAW
What do you think?
That proposal looks really good. It basically means, from a Ctlra
POV, that Ctlra is plain old C code, and exposes generic events.
The application can interpret those in whatever way it wants -
OSC, JS/Mixxx, or however OpenAV stuff will end up doing this. It
keeps Ctlra just generic events, and allows the application to
solve the mapping problem in its own way. That sounds logical and
a good abstraction, which is exactly what Ctlra aims for.
In order to progress this idea, I'll post code up ASAP, which
makes the generic Ctlra events available in a callback as part of
the CtlraController class. After that, the Mixxx/JS components
must be designed / worked on to fully enable Ctlra in Mixxx.
Thanks for all the input - we seem to be converging on a solution,
great! -Harry
Am 09.07.2017 um 06:52 schrieb Be:
Hi Harry,
I read the paper for the presentation at LAC 2017 that you
linked on IRC:
http://musinf.univ-st-etienne.fr/lac2017/pdfs/01_C_E_137795.pdf
<http://musinf.univ-st-etienne.fr/lac2017/pdfs/01_C_E_137795.pdf>
Going along with what I mentioned in my previous post, I do
not think Ctlra should be aware of the "userdata". IMO that
should be left to the application and its scripting environment.
On 07/08/2017 08:36 PM, Be wrote:
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
<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 <http://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>
<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/
<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
<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
<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
<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>
<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>
<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>
<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>
<https://github.com/openAVproductions/openAV-ctlra>
<https://github.com/openAVproductions/openAV-ctlra>
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