Using Csound
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## Using Csound

Csound can be operated in a variety of modes and configurations. The original method for running Csound was as a console program (DOS prompt for Windows, Terminal for Mac OS X). This, of course, still works. Running csound without any arguments prints out a list of command-line options, which are more fully explained in the Command Line Flags (by Category) section. Normally, the user executes something like:

    csound myfile.csd

or separate orchestra (orc) and score (sco) files can be used:

    csound myorchestra.orc myscore.sco

You can find many .csd files in the examples folder. Most opcode entries in this manual also include simple .csd files showing the usage of the opcode.

There are also many Front-Ends which can be used to run csound. A Front-End is a graphical program that eases the process of running csound, and sometimes provides editing and composing functions.

Csound also has several ways of producing output. It can:

- Read and write soundfiles (off-line rendering) - Using the -o and -i flags specifying an output filename.
- Read and write digital audio using a sound card (real-time rendering) - Using the -odac and -iadc flags
- Read and write MIDI files (non-realtime) - Using the -F and --midioutfile flags.
- Read and write MIDI using a MIDI interface and controller (real-time control) - Using the -M and -Q flags.

## Csound's Console Output

When Csound runs, it prints a text output to the console, which shows data about the Csound run. A Console output looks something like this:

    time resolution is 0.455 ns
    PortMIDI real time MIDI plugin for Csound
    virtual_keyboard real time MIDI plugin for Csound
    PortAudio real-time audio module for Csound
    0dBFS level = 32768.0
    Csound version 5.10 beta (float samples) Apr 19 2009
    libsndfile-1.0.17
    Reading options from $HOME/.csoundrc
    UnifiedCSD:  oscil.csd
    STARTING FILE
    Creating options
    Creating orchestra
    Creating score
    orchname:  /tmp/csound-XYACV6.orc
    scorename: /tmp/csound-IYtLAJ.sco
    rtaudio: ALSA module enabled
    rtmidi: PortMIDI module enabled
    orch compiler:
    17 lines read
            instr   1
    Elapsed time at end of orchestra compile: real: 0.129s, CPU: 0.020s
    sorting score ...
            ... done
    Elapsed time at end of score sort: real: 0.130s, CPU: 0.020s
    Csound version 5.10 beta (float samples) Apr 19 2009
    displays suppressed
    0dBFS level = 32768.0
    orch now loaded
    audio buffered in 256 sample-frame blocks
    ALSA input: total buffer size: 1024, period size: 256
    reading 1024-byte blks of shorts from adc (RAW)
    ALSA output: total buffer size: 1024, period size: 256
    writing 1024-byte blks of shorts to dac
    SECTION 1:
    ftable 1:
    new alloc for instr 1:
    B  0.000 ..  2.000 T  2.000 TT  2.000 M:  10000.0  10000.0
    Score finished in csoundPerform().
    inactive allocs returned to freespace
    end of score.              overall amps:  10000.0  10000.0
               overall samples out of range:        0        0
    0 errors in performance
    Elapsed time at end of performance: real: 2.341s, CPU: 0.050s
    345 1024-byte soundblks of shorts written to dac
    Removing temporary file /tmp/csound-CoVcrm.srt ...
    Removing temporary file /tmp/csound-IYtLAJ.sco ...
    Removing temporary file /tmp/csound-XYACV6.orc ...

The console output of Csound is quite verbose, particularly before the actual performance (like version, plugins loaded, etc.). Performance actually started when the console printed:

    SECTION 1:

In this particular run, the lines:

    new alloc for instr 1:
    B  0.000 ..  2.000 T  2.000 TT  2.000 M:  10000.0  10000.0

Show that a single note for instrument 1, that lasted 2 seconds starting at time 0.000, was produced with an amplitude of 10000 for both channel 1 and 2. An important section of the console output is:

    end of score.              overall amps:  10000.0  10000.0
               overall samples out of range:        0        0

Which shows the overall amplitude and the number of samples which were clipped because they were out of range.

The line:

    Elapsed time at end of performance: real: 2.341s, CPU: 0.050s

Shows the clock time and the CPU time it takes for the processor to complete the task. If CPU time is lower than clock time it means the csd can run in realtime (unless it has some sections which are extremely CPU intensive). The "real time" figure is the total running time and it is larger because it acounts for disk access. module loading, etc. (CPU time is strictly number-crunching time). If you have a sound that lasts for 100s and it takes 5s to generate it offline, it means that you are taking around 5% of CPU, and that it runs on 0.05 of realtime.

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