[ardour.git] / manual / xml / jack.xml

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<section id="sn-configuring-jack">
        <title>Getting Audio In, Out and Around Your Computer</title>
        <para>
                Before you can begin to use Ardour, you will need to get the audio
                input/output capabilities of your system working and properly configured.
                There are two aspects to this process: getting your audio interface
                (soundcard) working, and configuring it to work with the Jack Audio
                Connection Kit (<ulink url="http://jackaudio.org/">JACK</ulink>).
        </para>

        <section id="sn-jack">
                <title>JACK</title>
                <para>
                        It is extremely important to understand that Ardour does not interact
                        directly with your audio interface when it is running. Instead, all of the
                        audio data signals that Ardour receives and generates are sent to and from
                        JACK, a piece of software that routes audio data between an audio interface
                        and audio applications, in real time.
                </para>

                <para>
                        Traditionally, most of the audio sources that you would want to record, as
                        well as a lot of the more significant effects processing, existed outside
                        the computer. Consequently one of the biggest issues in integrating a
                        computer into the operation of the studio is how to move audio data in and
                        out of the computer.
                </para>

                <para>
                        However, it is becoming increasingly common for studios to use audio
                        sources and effects processing that are comprised completely of software,
                        quite often running on the same machine as an audio sequencer or digital
                        audio workstation (DAW). A new problem arises in such situations, because
                        moving audio in and out of the DAW no longer involves your hardware audio
                        interface. Instead, data has to be moved from one piece of software to
                        another, preferably with the same kind of sample synchronisation you’d
                        have in a properly configured digital hardware system. This is a problem
                        that has been solved at least a couple of times (ReWire from PropellerHeads
                        and DirectConnect from Digidesign are the two most common examples), but
                        JACK is a new design developed as an open source software project, and is
                        thusly available for anyone to use, learn from, extend, *fix or modify.
                </para>

                <para>
                        New users may not initially realize that by using Jack, their computer
                        becomes an extremely flexible and powerful audio tool - especially with
                        Ardour acting as the ’heart’ of the system.
                </para>
        </section>

        <section id="getting-audio-working">
                <title>Getting Your Audio Interface Working</title>
                <note>
                        <para>
                                Although Ardour runs on OS X as well as Linux, this documentation
                                describes only a Linux (ALSA) system. The issues faced on OS X tend to be
                                entirely different, and are centered mostly on JACK. There are also
                                alternative audio device driver families for Linux but they are also not
                                discussed here.
                        </para>
                </note>

                <para>
                        Getting your audio interface working can be the hardest part of setting
                        your computer up to run Ardour, or it could be one of the easiest. The
                        level of difficulty you will face depends on the type of audio interface
                        ("soundcard") you are using, the operating system version you are using,
                        and your own understanding of how it all works.
                </para>

                <para>
                        In an ideal world, your computer already has a working audio interface, and
                        all you need do is to start up qjackctl and run JACK. You can determine if
                        you face this ideal situation by doing a few simple tests on your machine.
                        The most obvious test is whether you’ve already heard audio coming out of
                        your computer. If you are in this situation, you can skip ahead to
                        <xref linkend="selecting-capture-source"/>.
                </para>
        </section>

        <section id="checking-for-an-audio-interface">
                <title>Checking For an Audio Interface</title>
                <para>
                        If you’ve never tried to play audio on your computer before, you should
                        use a basic playback program such as play, aplay or possibly xmms. Find an
                        audio file on your machine (<command>locate .wav</command> may help here),
                        and try to play it. There are several possibilities:
                </para>

                <itemizedlist>
                        <listitem>
                                <para>
                                        You may get an error from the program
                                </para>
                        </listitem>
                        <listitem>
                                <para>
                                        You may hear nothing
                                </para>
                        </listitem>
                        <listitem>
                                <para>
                                        You may hear something, but its too quiet
                                </para>
                        </listitem>
                        <listitem>
                                <para>
                                        you may hear something from the wrong loudspeakers.
                                </para>
                        </listitem>
                </itemizedlist>
        </section>

        <section id="selecting-capture-source">
                <title>Selecting Capture Source</title>
                <para>
                        Many audio interfaces, particularly the cheaper varieties that are often
                        found built into computers, have ways to plug in both microphones and
                        instruments or other audio equipment to be recorded. This immediately poses
                        a question: how does Ardour (or any software) know which signal to record,
                        the one coming into the microphone input, or the one arriving at the "line
                        in" socket? The same question arises also for "high-end" audio interfaces,
                        though in different ways.
                </para>

                <para>
                        The short answer is: Ardour doesn’t. Instead, this is a choice you have
                        to make using a program a program that understands how to control the
                        mixing hardware on the audio interface. Linux/ALSA has a number of such
                        programs: alsamixer, gamix, aumix, kmix are just a few of them. Each of
                        them offers you a way to select which of the possible recordable signals
                        will be used for as the "capture source". How you select the preferred
                        signal varies from program to program, so you will have to consult the help
                        documentation for whichever program you choose to use.
                </para>

                <para>
                        There are also a few programs that offer ways to control just one
                        particular kind of audio interface. For example, the
                        <application>hdspmixer</application> program offers control over the very
                        powerful matrix mixer present on several RME audio interface.
                        <application>envy24ctrl</application> does the same for a number of
                        interfaces built around the common ice1712/envy24 chipset, found in devices
                        from M-Audio, Terratec and others. Please note that this quite similar to
                        the situation for Windows and MacOS users, where each audio interface often
                        comes with its own control program that allows certain critical
                        configuration choices to be made.
                </para>

                <section id="problems-with-input-signal">
                        <title>"I don’t get any signal when I record …"</title>
                        <para>
                                The most common problem for first-time audio users on Linux is to try to
                                record something and get no signal at all, or alternatively, a very low
                                signal. The low signal problem typically arises from one or more of the
                                following issues:
                        </para>

                        <itemizedlist>
                                <listitem>
                                        <para>
                                                a microphone input plugged into the "line in" socket of the interface.
                                                The signal levels delivered by microphones are very small, and require
                                                amplification before they can be used by most audio circuitry. In
                                                professional recording studios, this is done using a dedicated box
                                                called a "pre-amplifier". If your audio interface has a "mic input"
                                                socket, then it has its own pre-amplifier built in, although its
                                                probably not a very good one. If you make the mistake of plugging a
                                                microphone into the "line in" socket, you will get either an inaudible
                                                or very quiet signal.
                                        </para>
                                </listitem>
                                <listitem>
                                        <para>
                                                the wrong capture source selected in the audio interface’s hardware
                                                mixer (see above)
                                        </para>
                                </listitem>
                                <listitem>
                                        <para>
                                                the "capture" gain level in the audio interface’s hardware mixer is
                                                turned down too low. You will need to use a hardware mixer application
                                                (as described above) to increase this.
                                        </para>
                                </listitem>
                        </itemizedlist>

                        <note>
                                <para>
                                        You will notice in the mixer strip for each track in ardour that you can
                                        change the selection of the monitoring source between input/pre/post.
                                        Adjusting the fader while watching the ’input’ levels will NOT have
                                        any affect on the levels. As mentioned above, ardour is dependent on
                                        external mixer settings for a source level.
                                </para>
                        </note>
                </section>
        </section>

        <section id="monitoring-choices">
                <title>Monitoring Choices</title>
                <para>
                        Its unfortunate that we have to raise this issue at a point in the manual
                        where you, the reader, may not even knoiw what "monitoring" means. However,
                        it is such an absolutely critical aspect of using any digital audio
                        workstation that we need to at least cover the basics here. The only people
                        who don’t need to care about monitoring are those who will never use
                        ardour to record a live performance (even on performed using a software
                        synthesizer).
                </para>

                <para>
                        Monitoring is the term we use to describe listening to what ardour is
                        recording. If you are playing a guitar and recording it with ardour, you
                        can probably hear the guitar’s own sound, but there are many situations
                        where relying on the sound of the instrument is completely inadequate. For
                        example, with an electronic instrument, there is no sound until the
                        electrical signal that it generates has been processed by an amplifier and
                        fed to a loudspeaker. But if Ardour is recording the instrument’s signal,
                        what is responsible for sending it to the amp+loudspeakers? It can get a
                        lot more complex than that: if you are recording multiple performers at the
                        same time, each performer needs to hear their own playing/singing, but they
                        also probably need to hear some of their colleagues’ sound as well. You
                        might be overdubbing yourself - playing a new line on an instrument while
                        listening to tracks you’ve already recorded - how do you hear the new
                        material as well as the existing stuff?
                </para>

                <para>
                        Well, hopefully, you’re convinced that there are some questions to be
                        dealt with surrounding monitoring, see <xref linkend="sn-monitoring"/> for
                        more in depth information.
                </para>
        </section>

        <section id="using-multiple-soundcards">
                <title>Can I use multiple soundcards</title>
                <para>
                        There are really lots of great reasons why you should not even attempt to
                        do this. But seriously, save your money for a while and buy yourself a
                        properly designed multichannel soundcard.
                </para>
        </section>

        <section id="qjackctl">
                <title>Qjackctl</title>
                <para>
                        JACK itself does not come with graphical user interface - to start JACK and
                        control it you need to have access to a command line and a basic knowledge
                        of Unix-like operating systems. However,
                        <ulink url="http://qjackctl.sourceforge.net/">qjackctl</ulink> is a
                        wonderful application that wraps JACK up with a graphical interface that is
                        both nice to look at and useful at same time. qjackctl is the recommended
                        way of using JACK.
                </para>
                <mediaobject>
                        <imageobject>
                                <imagedata fileref="images/qjackctl.png"/>
                        </imageobject>
                </mediaobject>
                <para>
                        You should be able to start qjackctl from the “application menu” of
                        your system, typically found on the panel/appbar/dock or whatever its
                        called that lives at the top/bottom/left/right of your screen.
                </para>

                <para>
                        [ need screenshot of GNOME/KDE/OSX menus here ]
                </para>
        </section>
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