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7 <section id="sn-monitoring">
8 <title>Monitoring</title>
10 If you are recording an acoustic instrument or voice with no
11 pre-existing recorded material as an accompaniment, then you probably
12 don't need to worry about monitoring. Just make sure you've made the
13 right <link linkend="sn-jack">connections</link> and you should be ready
14 to record without reading this section.
18 However, if a musician is playing an instrument (it doesn't matter what
19 kind) while listening to some pre-existing material, then it is
20 important that some mechanism exists to allow her to hear both her own
21 playing and the accompaniment. The same is true in a slightly different
22 way if the instrument makes no sound until the electrical signal it
23 creates has been amplified and fed to some loudspeakers. Listening to
24 the performance in this way is called monitoring.
28 So, if you are recording an electrical or software instrument/signal,
29 and/or the musician wants to listen to existing material while
30 performing, then you need to ensure that signal routing is setup to
31 allow monitoring. You have 2 basic choices:
34 <section id="hardware-monitoring">
35 <title>Hardware Monitoring</title>
37 Hardware monitoring uses the capabilities of your audio interface to
38 route an incoming signal (e.g. someone playing a guitar into a
39 microphone) to an output connection (for example, the speaker outputs,
40 or a dedicated analog monitoring stereo pair). Most audio interfaces
41 can do this, but how you get them to do so, and what else they can do
42 varies greatly. We can divide audio interfaces into 3 general
49 relatively simple, typically stereo, devices that allow the signal
50 being recorded to be routed back to the main outputs (most
51 "consumer" audio interfaces fit this description, along with
52 anything that provides an "AC97-compliant CODEC")
58 multichannel devices that allow a given input channel to be routed
59 back to its corresponding output channel (the main example is the
66 multichannel devices that allow any input channel, along with any
67 playback channel, to be routed to any output channel (the RME HDSP
68 and various interfaces based on the envy24/ice1712 chipsets, such
69 as the M-Audio Delta 1010, EZ-8 and various Terratec cards)
74 <section id="monitoring-consumer-audio-interfaces">
75 <title>"Consumer" audio interfaces and monitoring</title>
77 For interfaces in the first category, there is no standard method of
78 getting the signal routing correct. The variations in the wiring of
79 hardware mixing chips, and the capabilities of those chips, means
80 that you will have to get familiar with a hardware mixer control
81 program and the details of your audio interface. In the simple
82 cases, simply increasing the level named "Line In" or "Mic" in the
83 hardware mixer control program will suffice. But this is not a
84 general rule, because there is no general rule.
88 The following diagram shows a fairly typical AC97-based audio
93 <imagedata fileref="images/simplemixer.png"/>
103 there are multiple input connections, but only one can be used
104 as the capture source
110 it is (normally) possible to route the input signals back to the
111 outputs, and independently control the gain for this "monitored"
118 it may or may not be possible to choose the playback stream as
125 <section id="monitoring-prosumer-audio-interfaces">
126 <title>High end "prosumer" interfaces and monitoring</title>
128 For the only interface in the second category, the RME Digi9652
129 ("Hammerfall"), the direct monitoring facilities are simplistic but
130 useful in some circumstances. They are best controlled using
131 <emphasis>JACK hardware monitoring</emphasis>.
135 When using one of the interfaces in the third category, most people
136 find it useful to use hardware monitoring, but prefer to control it
137 using a dedicated hardware mixer control program. If you have an RME
138 HDSP system, then <command>hdspmixer</command> is the relevant
139 program. For interfaces based on the envy24/ice1712/ice1724
140 chipsets, such as the Delta1010, Terratecs and others,
141 <command>envy24ctl</command> is the right choice. Both programs
142 offer access to very powerful matrix mixers that permit many
143 different variations on signal routing, for both incoming signals
144 and the signals being played back by the computer. You will need to
145 spend some time working with these programs to grasp their potential
146 and their usage in different situations.
150 The following diagram gives a partial view of the monitoring
151 schemantics for this class of audio interface. Each input can be
152 routed back to any output, and each such routing has its own gain
153 control. The diagram only shows the routings for "in1" to avoid
154 becoming completely incomprehensible.
158 <imagedata fileref="images/matrixmixer.png"/>
164 <section id="jack-hardware-monitoring">
165 <title>JACK hardware monitoring</title>
169 <section id="software-monitoring">
170 <title>Software monitoring</title>
172 Much simpler than hardware monitoring is "software monitoring". This
173 means that any incoming signal (say, through a Line In connector) is
174 delivered to software (such as Ardour) which can then deliver it back
175 to any output it chooses, possibly having subjected it to various
176 processing beforehand. The software can also mix signals together
177 before delivering them back to the output. The fact that software
178 monitoring can blend together incoming audio with pre-recorded
179 material while adjusting for latency and other factors is the big plus
180 for this method. The major downside is latency. There will always be a
181 delay between the signal arriving at your audio interface inputs and
182 it re-emerging from the outputs, and if this delay is too long, it can
183 cause problems for the performer who is listening. They will sense a
184 delay between pressing a key/pulling the bow/hitting the drum etc. and
185 hearing the sound it produces.
189 However, if your system is capable of low latency audio, its likely
190 that you can use software monitoring effectively if it suits your
195 <section id="controlling-monitoring-within-ardour">
196 <title>Controlling monitoring choices within Ardour</title>
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