====== DVswitch remote control ======
~~DRAFT~~

[[http://dvswitch.alioth.debian.org/|DVswitch]] is an application that allows interactive live-mixing of DV-sources with emphasis on streaming and archiving conference presentations. 

This article describes a method that was [[http://lists.alioth.debian.org/pipermail/dvswitch-devel/2012-February/000548.html|outlined on the dvswitch mailing-list]] to allow interacting with dvswitch using external control mechanisms, such as physical buttons, sliders or apps running on a tablet or phone. To that end dvswitch has been extended to send and react on [[http://opensoundcontrol.org|OSC]] messages.

Before delving into the details here's a quick demo-video:

<flashplayer width=640 height=504 position=1>file=/_media/pub/av/dvosc2.flv&autostart=false&icons=false</flashplayer>

===== Architecture =====

The concept is to create a generic interface that allows to remote-control dvswitch and specific applications for various setups and use-cases that use this control-interface. The general idea is that one can use an interface appropriate for the job at hand. OSC is easily accessible: Commandline-tools, OSC controller-apps for touch-screen phones and OSC-sequencing software are available.
 
A first specific application used for prototyping is a MIDI -> OSC translator called 'dvmctrl'.

<ditaa name=dvmctrl1>

/------\          +-----------+          +----------+
|      |          |cYEL       |          |cYEL      |
| Midi |  Midi    |           |   OSC    |          |
|      +--------->|  dvmctrl  +--------->| dvswitch |
| Desk |          |           |          |          |
|      |          |           |          |          |
\------/          +-----------+          +----------+

</ditaa>

In its current development state dvmctrl binds MIDI control-commands (from a BCF2000 MIDI-Desk) to dvswitch actions. It is intended to be used with three DV-source (two camera, one projector input), as demoed in the video above. 

===== OSC control messages =====

The patched dvswitch interprets the following OSC messages:

^  osc-msg  ^  type  ^ ^
|/dvswitch/src/pri     |  i  |select primary video-input [0..] |
|/dvswitch/src/sec     |  i  |select secondary video-input [0..] |
|/dvswitch/src/snd     |  i  |select audio-input [0..] |
|/dvswitch/rec/start   |     |send record-start command. |
|/dvswitch/rec/stop    |     |send record-stop command. |
|/dvswitch/rec/cut     |     |send record-cut command. |
|/dvswitch/fx/overlay  |  i  |set A/B overlay [0..255]; 0: source A, 255: source B |
|/dvswitch/fx/fade     |  i  |switch to A->A' fade-effect [50..15000]ms; 0:cancel-effect|
|/dvswitch/fx/pip      |  i  |//experimental// picture-in-picture [0..4]; 0: cancel-effect, 1-4 pip-position presets |
|/dvswitch/fx/pip      |  fff  |//experimental// picture-in-picture effect - params: x-pos, y-pos, size; all [0..1]. any value <0 will cancel the effect. |


===== Source Code =====

There are a couple of build-prerequisites to compile this beast: in particular development packages for ffmpeg (libavformat-dev, libavcodec-dev,..), cairo and cairomm, freetype, pango, jack, cmake, etc. for dvswitch; liblo-dev, alsa-dev and gnu-make for dvmctrl.

The source code of the patched dvswitch((the patch include a jack-audio-input, video-overlay/fade and OSC control)) and dvmctrl is kept in git repositories
  * http://rg42.org/gitweb/?p=dvswitch.git
  * http://rg42.org/gitweb/?p=dvmctrl.git

  git clone git://rg42.org/dvswitch  ## this checks out the "0.9-osc" branch by default
  cd dvswitch
  mkdir build; cd build
  cmake ..
  make
  ./src/dvswitch -o 5675 ## works IFF dvswitch is avail on the system (/usr/share/dvswitch/*png)
                         ## otherwise you will need to install the built


  git clone git://rg42.org/dvmctrl
  cd dvmctrl
  make
  ./dvmctrl # -m BCF2000 -o 5675 (these are defaults)

Now add three sources in order: cam-1, cam-2, slides/projector using dvsource-*.

===== Known Problems =====

The setup has been tested successfully for >24 hours of continuous operation - although the settings were rather static for most of the time. 

A potential problem is that the the input sources must to be in fixed order for the duration of a session (particularly the video-projector - here #3 which is mapped to the fader). When a source is disconnected or dropped from dvswitch and re-connected the ordering is not necessarily identical.

This can be worked-around in 'dvmctrl' (re-map the sources) but should rather be fixed in dvsource and dvswitch itself.

===== TODO =====

  * optimize the interaction design (midi-button mapping - possibly midi learn; dynamic maps)
  * fix or work-around the mixer::source_id sort ordering (see known problems)
  * add midi-map for record, and stop.
  * make dvswitch send status information via OSC (code is prepared but no hooks are yet defined)
    * send info about currently active sources (tally lights)
    * send notifications about new sources or sources going away.
    * transmit updates done via mouse or keyboard.
  * ...
  * clean up the patches for upstream inclusion


{{tag>floss video}}