man siggen.conf (5): the siggen configuration files

SYNOPSIS

siggen.conf

DESCRIPTION

As from siggen version 2.3 onwards a versatile configuration file scheme has been introduced. It allows parameters for the siggen programs to be specified either across the board, or specifically for particular programs.

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 programs are compiled with the names of the config files built in. The filenames are set in the config.h header file and can be changed. The LOCAL and GLOBAL config files are specified by the settings of:

LOCAL: #define DEF_CONF_FILENAME ".siggen.conf"
GLOBAL: #define DEF_GLOBAL_CONF_FILE "/etc/siggen.conf"

And can be set to any file name or to NULL to disable the file. The HOME config filename is created using the $HOME environment variable and the DEF_CONF_FILENAME together, i.e. using the above, the HOME config file for a user whose home directory is at /home/jj, would be

HOME: /home/jj/.siggen.conf

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 programs themselves provide builtin default values (see config.h etc), and most of these values can be set by appropriate command line switches and flags.

CONFIGURATION VALUES

A configuration value has a name and a value, and values for all programs are set by simply entering a line in the appropriate config file where the first word is the name, followed by arbitrary spaces/tabs, followed by the value. The value is all the rest of that line. e.g. to set the global default samplerate of 44100 samples per sec, the following line would be entered in the GLOBAL config file:

SAMPLERATE 44100

Config value names are case insensitive.

A config value can be set for a specific program, by prefixing the config value name with the program name and a ':'. e.g. to specify a samplerate of only 8000 samples per sec for the tones program enter

TONES:SAMPLERATE 8000

in the relevant config file. If both lines above were in the config file, all programs except tones would use a samplerate of 44100, and tones would use 8000.

You do not have to specify all configuration values in the config files. If a particular value is missing, the programs will simply use their builtin defaults (see config.h etc).

Configuration values set by command line switches or flags take precedence over values in any of the config files.

Beware

the programs do not have their 'name' built-in, but use the name they were invoked by. So if you change the name of a program, remember to change the config file entries. However this does means that by using links to a program, it can be made to pick up a different set of configuration values, depending on the name it is invoked by.

EXAMPLE CONFIGURATION FILE

A sample config file is provided in ".siggen.conf" in the distribution. This may also be at /etc/siggen.conf . Any line whose first non-whitespace character is a '#', is a comment line and is ignored.

WHAT CONFIGURATION VALUES ARE THERE?

Not all of the siggen programs use all the values described here. See the relevant man page for which values are used by which programs.

CHANNELS

In all programs except tones and fsynth, channels specifies the number of output channels to use, i.e. 1 for Mono and 2 for Stereo.

For tones, channels specifies the number of 'voices' on which tones can generate different waveforms before mixing them into the one output channel.

For fsynth, channels specifies the numbers of separately configurable oscillators used to mix the single output channel.

DACFILE

The Digital to Analogue Converter (or PCM or DSP) device on which to output the generated samples. This must be a real OSS PCM device, otherwise the ioctls used will fail.

FRAGMENTS

The number of Audio Buffer fragments to configure in the driver. The interactive programs respond to changes made to parameters from the keyboard immediately, but data will be buffered in the driver in the buffer fragments. If the amount of data buffered is too much then there will very noticeable delays before the output sound is altered. Against that, insufficient buffering may mean that there is not enough data buffered for output to cover the time when other processes are being run by the scheduler. The programs set the buffer size to the nearest power of 2 to give aprox. 100millisecs of sound. Hence if FRAGMENTS is set to 3, there will be aprox. 0.3 secs worth of sound buffered for output. On a lightly loaded fast machine this, or 2, should be sufficient. To cover periods of heavy load or on a less powerful machine use 4 or 5. But remember the interactive programs will appear sluggish in responding to the keyboard.
SAMPLERATE

The number of samples per second to use. If output is to the DAC then the DAC device is set to output samples at this rate.
BEWARE: not all cards can support all samplerates. SoundBlasters are fairly flexible in this respect. Other cheaper cards are not. Indeed some cards can only handle a very restricted set of related samplerates e.g. 11025, 22050, 44100 & 8000, 16000, 32000, 48000. When writing to DACFILE all programs will attempt to set the samplerate given, but use the actual samplerate the device used. Use the verbose command line flag to check actual samplerates used.

Some common samplerates used are:

8000

is the samplerate used in the phone system with 8 bit samples, and is adequate for voice range frequencies.     44100

is the samplerate used in audio CDs     48000

is the samplerate used in DAT systems, I think, and for much professional kit.     32000

is also used, but I forget where, minidisc?.

In general, the higher the samplerate the larger the memory and processing requirement, but the higher the frequency range and the more accurate the signals generated.

SAMPLESIZE

Number of bits per sample. Only two values are allowed currently, 8 or 16. 8

bit samples are unsigned, with decimal value 128 being the 'zero' level. 16

bit samples are signed little endian values, i.e. the least significant byte comes before the most significant byte either in a file, or in the byte stream to an output device.

If samplesize if left completely unspecified, then all programs will attempt to do 16 bit samples to DACFILE, and if that isn't possible will do 8 bit samples. Or if writing to a file, 16 bit samples will be written.

VERBOSE

sets verbosity level.     0

is quiet     1

is be a bit verbose (equiv. to -v switch)     2

is be very verbose (equiv. to -vv switch)

VI_KEYS

if set to a non-zero value, then the VI cursor moving keys "HJKL" are enabled.

BUGS

COPYING

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: [email protected]