livetrax/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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