More about channels.

[nageru-docs] / gettingstarted.rst

Getting started
===============

Welcome to Nageru! For simple use, you can jump right in and make yourself
comfortable (at least if you have the :doc:`hardware requirements <hardware>`
in place), but if you prefer a gentler introduction, this is the place.


Introduction to the M/E workflow
--------------------------------

Nageru, like most hardware video mixers, is based on the **mixer/effects**
workflow, or just M/E for short. (Don't ask why “mixer” or “effects”;
the name is confusing and mostly historical.)

The basic idea of M/E is that you have two main displays, *preview* and *live*.
Every time you want to change what's shown to the viewer, you first bring it
up on the preview display, verify that it indeed contains something you'd like
to show to your viewers, and only then start a transition to move the preview
display onto the live display (which mirrors exactly what the viewers see).
After the transition is done, the preview and live displays switch, allowing
the operator to either switch back or to pull a new source onto the preview
display.

In Nageru, the available transitions at any time are governed by the
:doc:`theme </theme>`. However, generally a simple cut (moving immediately
from live to preview) will nearly always be an option. Other effects include
fades and zooms, but availability will depend on what sources are involved in the
transition.


A brief tour of the Nageru UI
-----------------------------

The basic Nageru UI with the default theme looks like this:

.. image:: images/basic-ui.png

First a word about user input: Nageru can be controlled by the mouse or
keyboard, but most operators will prefer using both hands on the keyboard.
Like on a real mixing console, you use your left hand to select sources for
preview (using the 1–9 keys) and the right hand to choose a transition
(using J, K or L). In addition, audio can be controlled using a MIDI controller
if you want to; see the :doc:`audio <audio>` page for more information.


Channels
''''''''

The preview and live displays are the most important part of the UI,
and thus take up the bulk of the space. In addition, we have the list
of channels and scenes (the side-by-side view and the static image)
along the bottom. As you can see, we have only
one (rather boring) input connected, and it is live. The other input is
disconnected and thus shows only a test color. These correspond to pressing
the 1 and 2 keys on the keyboard to activate preview, respectively—or you can
left-click on them do achieve the same effect. (Right-clicking will bring up
:ref:`the video card context menu <context-menu>`; see below.)

Similarly, we have a side-by-side view; it is composed of a big image of
input 1 and a smaller one of input 2. (If you are unhappy which is which,
you can switch the two inputs; again, see below.)

Finally, we have a static image. The one included with Nageru is rather
bland and generic, but it works as a generic pause image when you don't
really want anything on the screen.

For any given channel, you can see that it is active in the live or preview
by looking at its border. If it's got a red border, as in the leftmost
input, it's live (either on its own, or as part of the side-by-side view).
Similarly, if it's got a green border, as in the second input (you can
see it if you look closely; it's a somewhat lighter shade of green),
it will be marked with green. On conflict, red (live) wins, since it is
the most important piece of information.


Transitions
'''''''''''

Whenever you have a different channel pulled up on the preview from
on the live display, you will see that the three buttons in the middle
offer you various **transitions**. Selecting any of them (either by
the displayed hotkey, or using the mouse) will *swap* the preview and
live inputs, effectively making the preview live. If you use “cut”,
this will happen nearly instantly; the two other options, zoom
(only available with the side-by-side view) and fade (*not* available
with the side-by-side view) take some time, as you can see in the live view.

A good operator knows to use the right transition at the right time,
so that the end result does not distract from the actual message
of the video. In particular, too frequent switching between sources
will probably be perceived as disturbing.


The audio strip
'''''''''''''''

The look of the audio strip will vary significantly with what audio
mode you are in; the default is the simple mode, but multichannel
is much more powerful. Both modes, as well as the level meters on
the right, are explained in detail in the section about :doc:`audio <audio>`.


The menu bar
''''''''''''

The menu bar does not contain a lot of interesting information,
but it does have a few elements that are useful for configuration.
The video menu contains the following elements:

  * **Begin new video segment:** Nageru is constantly recording
    your stream to disk in a near-lossless H.264 stream
    (you cannot turn it off, because experience shows you'd probably
    forget to turn it back on again in time for actual use);
    see :doc:`streaming` for more information. This option allows
    you to end the current file and begin a new one—the two files
    can be spliced back later for a 100% seamless result if you wish,
    so this is a lossless operation. It is typically useful
    to do this right before and after the event itself starts,
    so as to facilitate easier editing later.

    You can achieve the same effect as this option by sending
    SIGHUP to the Nageru process.

  * **Change x264 bitrate:** See :doc:`streaming` for more information.

  * **Exit:** Exits Nageru, obviously.

The audio menu is explained in the section on :doc:`audio <audio>`.

Finally, the menu bar also hosts the disk space meter. This shows
how much disk you have left before Nageru will error out and die;
it also tries to estimate how much real time this corresponds to,
based on the last 30 seconds of recording. 


.. _context-menu:

The video card context menu
'''''''''''''''''''''''''''

If you right-click on a channel that corresponds to a video input
(ie., not the side-by-side view or static image), a simple context menu
pops up:

.. image:: images/context-menu.png

The options presented are as follows:

 * **Input source:** Connect this video input to a different physical card,
   taking effect immediately. The theme supports only two inputs
   at a time (you can :doc:`write your own <theme>` that support many
   more if you wish), but if you start Nageru with a higher value
   for the “--num-cards” option (aka -c), you can choose any of the
   available ones here. This option is also useful if you want to
   switch the two cards, since input 1 is bigger in side-by-side mode.
   (See also the “--map-signal” option, aka -m.)

 * **Video input:** If a card supports multiple kinds of inputs
   (e.g. has both HDMI and analog inputs), you can select which one here.

 * **Audio input:** Similar, just for audio. “Embedded” means
   an audio stream that is included in the HDMI or SDI signal.

 * **Input mode:** Choose the video input mode to use. Note that the USB
   cards autodetect the mode, and you cannot override it even if you wanted to.
   For PCI cards, autodetection is not supported (even for the select few
   cards that can handle it in hardware), but a simple option (“Scan”)
   is available to try all modes in turn until a signal is received.

 * **Use as audio source:** See the :doc:`audio <audio>` page for more
   information. For simple audio only; unavailable in multichannel mode.

 * **Use as master clock:** The output stream needs exactly one stream
   as master clock. The frame rate and clocked will be locked exactly
   to it, so use the most important input here. A signal that keeps getting
   unplugged and replugged might not be the best candidate, although the
   PCI cards have fallback internal clocking when the signal is lost
   (the USB cards fall back to a strange mode of about 30.13 Hz).