Linux Certif

Toute la documentation sur la certification Linux LPI

tones

NAME

tones - a sequential tone generator program

SYNOPSIS

tones [options] [waveform] T freq(s)|notes(s)|command_file(s)

DESCRIPTION

tones generates one or more tones of various types (waveforms) and duration (T millisecs) of the specified frequencies or notes, or mixtures of frequencies or notes. See tones -h for a list of possible waveforms. The waveforms should include sine, cosine (90 degrees out of phase to sine), square (50% mark/space ratio), sawtooth (a ramp waveform), triangle and noise. Sine is the default. Besides the inbuilt waveforms, waveforms can be loaded from suitable WAV files - see below LOADABLE WAVEFORMS.

T is the default number of millisecs that each tone is to be played. Frequencies (freq(s)) are specified in Hertz as integers. A frequency of 0 causes T millisecs of silence to be played. Notes are specified as the musical note letter with an optional '#' to sharpen the note, then an octave number. Octaves run from C to C. Middle C is C3, the immediately preceding note is B2! The first Octave is from C0 to C1.

Several frequencies/notes can be played at once, by specifying the frequencies/notes required joined by a ',' character (but no spaces!).

e.g. 1000,1500,2000 specifies that the three frequencies are played together, all at the same relative level. See AMPLITUDES sections below for a discussion of how to set absolute amplitude levels or differing relative amplitudes for notes played together or serially.

Each freq specification can optionally contain a duration, by appending ':T', where 'T' is the duration in millisecs. This duration overrides the default. Also the default duration can be changed by using a the ':T' format on it's own - not appended to a freq spec.

e.g. 1200,600:1000 play the two freqs for 1 sec

e.g. c3,e3,g3 play the C major chord

e.g. :250 set the default tone duration to 250ms

Waveforms can be specified/altered at anytime. A single waveform name specifies that waveform to be used for all channels. Alternatively a comma (',') seperated list of waveforms can be given to specify or alter the waveform to use for a given channel. Ommitting a waveform in a list, means that the previous waveform is left unchanged.

e.g. square,,triangle specifies using square waves for chan 1, chan 2 is left unchanged, and triangular waves are used for channel 3.

The digital samples (either 8 or 16 bits) are played by default to the Linux /dev/dsp device at a samplerate of 22050 samples per second, in mono mode. (see CONFIGURATION FILES section below)

Fractional Hertz frequencies are not supported. Of course, only frequencies less than half the samplerate (number of samples/sec) can be accurately generated; but the program doesn't check this.

Instead of playing the output to /dev/dsp the samples can be written to a file as raw samples (-o file) or written in WAV format (-w wavfile). These data files can then be played back quickly with a raw data or WAV file player (e.g. wavplay) without the overhead of actually generating the samples.

There are some special 'commands' that can be specified, that may be useful in input files.

:N

Set default tone duration to N millisecs

@N

Set base amplitude level of tones when in absolute amplitude mode

absolute

Set absolute amplitude mode (see below)

echo

The rest of the line of the input file, or the rest of the command line parameter (NB to use quotes where necessary) is output to stdout.

relative

Set relative amplitude mode (see below)

reset|resync

All generator points are reset to the start of the waveform buffers. This forces subsequant generation of multiple frequencies/waveforms to be in phase.

Further, if the word is not one of the above, then tones checks to see if a file of that name exists, and if it does then the file is assumed to be a file of tones commands which are executed.

e.g. tones -v :100 tune1 tune2     will interpret and play the tones commands in files tune1 and tune2. This file processing is recursive. Files of commands can execute other files of commands etc. As usual, '-' can be used to specify stdin.

RELATIVE AMPLITUDES

tones by default works in a 'relative' amplitude mode, where the output level and sample range are maximally maintained. This ensures the best signal accuracy.

When specifying multiple frequencies/notes to be played together, then the relative amplitudes can be specified in deciBells by appending "@db" to the note.

e.g. 440,880@-12,1760@-30 specifies a mixture with 880Hz -12dB down, and 1760Hz -30dB down relative to the level of 440Hz. The mixed signal samples will span the full 16 or 8 bit range permitted for maximal signal accuracy.

The dB levels indicate the relative power levels. -3dB being at a relative power level of 0.5, -20dB being at a relative power level of 0.01 . However power levels are proportional to the square of the signal amplitude. So a signal at -6dB (quarter power) will only have its amplitude down by half. To reduce a signal amplitude by 1/10 then specify -20dB, i.e. a power level down by a factor of a hundredth.

dB levels can be specified as decimal values.

ABSOLUTE AMPLITUDES

tones can work in an absolute amplitude mode, where signal power levels are specified in deciBells (dB) relative to a 0dB level that indicates a peak value of +32767/-32768 for 16 bit signed samples, and 255/0 for 8 bit unsigned values. Hence any signal at a positive dB level will be clipped. Signals at a negative dB level will attentuated. If no level is specified then 0dB is assumed.

e.g. 500@-20,750@-6,1000,-12 gives 500Hz at -20db (amplitude 0.1), 750Hz at -6db (amplitude 0.5), and 1000Hz at -12dB (amplitude 0.25). The final mixed signal will have an amplitude of 0.1 + 0.5 + 0.25 = 0.85 or -1.4dB.

As can be seen, there is no "hands-free" in absolute mode. You have to work out the dB levels yourself and ensure that the resultant mixed signal does not go above 0dB and get clipped. Remember also that a sine wave at -80dB down (amplitude 1/10000th) only has 6 digital levels and is a pretty poor representation of a sine wave, not suitable for post amplification and use!

In absolute mode the base 'zero' level can be altered at any time by use of the @dB command. All subsequent dB levels specified will have this base level added to them.

e.g. @-20 1000,1200@+6,1400@-6 is the same as 1000Hz at -20dB, 1200Hz at -14dB and 1400Hz at -26dB.

LOADABLE WAVEFORMS

Given that the generation method used by tones to generate a waveform of FHz is simply to sequentially select every Fth sample from a buffer containing S samples of one complete waveform at a frequency of 1Hz (treating the buffer as circular, the beginning conceptually joined to the end), where S is the number of samples per second, it is possible to load a customised waveform from a WAV file containing the S samples of a 1Hz waveform. See the -load WavFile and -lw N options below. The name of the waveform is taken as the basename of the WavFile, i.e. with any trailing '.suffix' and leading path removed. Each loaded waveform should hence have this name unique, and different from the inbuilt waveform names.

The samples in WavFile should be 16 bit, mono, of the same number of samples as tones' playing samplerate, e.g. if tones is playing at 32000 samples per sec then the WavFile should contain 32000 16 bit samples. 16 bit samples are needed, because tones works internally with 16 bit samples, even if it is feeding 8 bit samples to the sound card or output file. Ideally the samples should span one complete wavelength, i.e. represent 1 second of a 1Hz signal. However this can be varied if used with some intelligence. If, say, 1 seconds worth of 5Hz of the waveform is used, then the output frequency will be 5 times higher than specified. If you have a mixture of 3Hz and 5Hz samples, then the frequencies generated will be a mixture of 3 and 5 times the frequency specified. I hope that is all understandable!

See the tones.eg directory for some examples of loadable modules and how tones itself can be used to generate the loadable waveforms.

OPTIONS

-8 | -b 8

set 8 bit unsigned data samples

-16 | -b 16

set 16 bit signed little-endian data samples.

-abs|-absolute

set absolute amplitude mode

-a

when used in conjunction with the -o option, data is appended to the file.

-C file

use "file" as the local configuration file (see below).

-c CHANNELS

set the maximum number of channels (concurrent played frequencies) to CHANNELS. The default number is 4. There is some virtue in keeping the number of channels to a minimum.

-f

when used in conjunction with the -o or -w options, any existing file is silently overwritten.

-h

display usage and help info

-i file

read frequencies/waveforms to generate from file 'file'. Reads from standard input if filename is '-'. Any command line specifications are actioned before the input file is read.

-l

play the tone sequence repetitively. Forced off if writing samples to a file with the -o or -w options.

-loop N

play the tone sequence N times.

-o file

write out samples to a raw data file. You will have to remember the data format, e.g. samplerate and 8/16 bit.

-rel|-relative

set relative amplitude mode

-s samplerate

set the number of samples per second to samplerate. For many simple uses a samplerate of 8000 is sufficient, making any saved data files smaller.

-w wavfile

write samples out in WAV format to wavfile. The WAV header contains details of whether the data is 8 or 16 bits and the sampling rate. You cannot use the append (-a) option with WAV files.

-v

be verbose

-lw N

Specify the number of loadable waveforms allowed, the default is 4

-load WavFile

Load the waveform from the WavFile.

EXAMPLES

tones 50 1000 700,1200 800,1100,1300

generates 3 50 millisecs sine tones, the first consisting of only 1000Hz, the second of 700Hz and 1200Hz and the third of 800Hz, 1100Hz and 1300Hz

tones -loop square 200 700 900 400 500

generates a sequence of 4 200 millisecs square wave tones which is repeated until the program is interupted.

tones -w seq.wav 70 1016 1200 1080 1150 1016

generates a sequence of 5 70 millisecs sine tones, and instead of playing them the samples are stored in WAV format in seq.wav which can be played by any WAV file player.

tones -w trap.wav :1000 triangle absolute 1@6

Generates a WAV file trap.wav consisting of a trapezoid waveform where the rise and fall slopes take up half the wavelength. A sawtooth is generated with a maximum that has twice the amplitude of the maximum sample sizes allowed, hence it is clipped flat for half the waveform period making a trapezoid shape.

tones -load trap.wav :1000 triangle 1000 trap 500 triangle,trap 1000,500

Will load the trapezoid waveform generated above as a new waveform called trap and then plays 1 seconds each of first a 1000Hz triangle wave, then a 500Hz trap waveform and finally both waveforms played together.

See also the tones.eg directory in the siggen distribution.

CONFIGURATION FILES

Three possible configuration files can be used: a LOCAL config file (usually in current directory), a HOME config file in user's $HOME directory and a GLOBAL config file.

All the siggen suite of programs are compiled with the names of the config files built in. By default the configuration files are:

./.siggen.conf

is the LOCAL config file.

$HOME/.siggen.conf

is the HOME config file.

/etc/siggen.conf

is the GLOBAL config file.

tones -h

will indicate which config files will be searched for.

The config files do not have to exist. If they exist and are readable by the program they are used, otherwise they are simply ignored.

The config files are always searched for configuration values in the order LOCAL, HOME, GLOBAL. This allows a scheme where the sysadmin sets up default config values in the GLOBAL config file, but allows a user to set some or all different values in their own HOME config file, and to set yet more specific values when run from a particular directory.

If no configuration files exist, the program provides builtin default values, and most of these values can be set by appropriate command line switches and flags.

See siggen.conf(5) for details of the configuration files.

tones looks for configuration values CHANNELS, DACFILE, SAMPLERATE, SAMPLESIZE, VERBOSE, LOADABLE_WAVEFORMS.

CHANNELS

sets the number of channels, see '-c' option.

DACFILE

allows the name of the DAC/DSP/PCM device to be changed from /dev/dsp

LOADABLE_WAVEFORMS

specifies the allowable number of loadable waveforms

SAMPLERATE

sets the number of samples/sec for the DAC device

SAMPLESIZE

sets whether 8 or 16 bit samples to be generated

VERBOSE

sets whether or not to run in verbose mode.

SEE ALSO

siggen.conf(5), signalgen(1), swgen(1)

 

BUGS

 

COPYING Copyright 1995-2008 Jim Jackson

The software described by this manual is covered by the GNU General Public License, Version 2, June 1991, issued by :

Free Software Foundation, Inc.,
675 Mass Ave,
Cambridge, MA 02139, USA

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be included in translation instead of in the original English.

AUTHOR

Jim Jackson

Email: jj@franjam.org.uk