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mpg123
!!!mpg123
NAME
SYNOPSIS
DESCRIPTION
OPTIONS
OPERANDS
HTTP SUPPORT
INTERRUPT
SEE ALSO
NOTES
BUGS
AUTHORS
----
!!NAME


mpg123 - play audio MPEG 1.0/2.0 file (layers 1, 2 and 3)
!!SYNOPSIS


__mpg123__ [[ __-tscvqy01m24wEC__ ] [[ __-b__
''size'' ] [[ __-k__ ''num'' ] [[ __-n__
''num'' ] [[ __-f__ ''factor'' ] [[ __-r__
''rate'' ] [[ __-g__ ''gain'' ] [[ __-a__
''dev'' ] [[ __-o s__ | __-o h__ | __-o l__ ] [[
__-d__ ''n'' ] [[ __-h__ ''n'' ] [[ __-w__
''file'' ] [[ __-p__ ''proxy'' ] [[ __-@__
''file'' ] ''file'' ... | ''URL'' ... |
__-__
!!DESCRIPTION


__mpg123__ reads one or more ''file''s (or standard
input if ``-'' is specified) or ''URL''s and plays them
on the audio device (default) or outputs them to stdout.
''file''/''URL'' is assumed to be an MPEG-1/2 audio
bit stream.
!!OPTIONS


__mpg123__ options may be either the traditional POSIX
one letter options, or the GNU style long options. POSIX
style options start with a single ``-'', while GNU long
options start with ``--''.


__-t__, __--test__


Test mode. The audio stream is decoded, but no output
occurs.


__-s__, __--stdout__


The decoded audio samples are written to standard output,
instead of playing them through the audio device. This
option must be used if your audio hardware is not supported
by __mpg123__. The output format is raw (headerless)
linear PCM audio data, 16 bit, stereo, host byte
order.


__-c__, __--check__


Check for filter range violations, and report them for each
frame if any occur. __-C__, __--control__ Enable
control keys. By default use 's' to stop, 'p' to pause, 'f'
to jump forward to the next song, 'b' to jump back to the
beginning of the song, ',' to rewind, '.' to fast forward,
and 'q' to quit.


__-v__, __--verbose__


Increase the verbosity level. For example, displays the
frame numbers during decoding.


__-q__, __--quiet__


Quiet. Suppress diagnostic messages.


__-y__, __--resync__


Try to resync and continue decoding if an error occurs in
the input file. Also try to recover from certain broken
headers. Useful if you have a broken MPEG file, on which
__mpg123__ normally gives up saying `Illegal header'. Be
careful: Broken locations in MPEG files might cause sharp,
loud pops or clicks, which might damage your speakers if
played too loud.


__-0__, __--single0__; __-1__,
__--single1__


Decode only channel 0 (left) or channel 1 (right),
respectively. These options are available for stereo MPEG
streams only.


__-m__, __--singlemix__


Mix both channels. This option is available for stereo MPEG
layer-3 streams only. It takes less CPU time than full
stereo decoding.


__-2__, __--2to1__; __-4__,
__--4to1__


Performs a downsampling of ratio 2:1 (22 kHz) or 4:1 (11
kHz) on the output stream, respectively. Saves some CPU
cycles, but at least the 4:1 ratio sounds ugly.


__-b__ ''size'', __--buffer__
''size''


Use an audio output buffer of ''size'' Kbytes. This is
useful to bypass short periods of heavy system activity,
which would normally cause the audio output to be
interrupted. You should specify a buffer size of at least
1024 (i.e. 1 Mb, which equals about 6 seconds of audio data)
or more; less than about 300 does not make much sense. The
default is 0, which turns buffering off.


__-k__ ''num'', __--skip__ ''num''


Skip first ''num'' frames. By default the decoding starts
at the first frame.


__-n__ ''num'', __--frames__
''num''


Decode only ''num'' frames. By default the complete
stream is decoded.


__-f__ ''factor'', __--scale__
''factor''


Change scale factor (default: 32768).


__-r__ ''rate'', __--rate__
''rate''


Set sample rate (default: automatic). You may want to change
this if you need a constant bitrate independed of the mpeg
stream rate. mpg123 automagically converts the rate. You
should then combine this with --stereo or
--mono.


__-g__ ''gain'', __--gain__
''gain''


Set audio hardware output gain (default: don't
change).


__-a__ ''dev'', __--audiodevice__
''dev''


Specify the audio device to use. The default is
system-dependent (usually /dev/audio or /dev/dsp). Use this
option if you have multiple audio devices and the default is
not what you want.


__-o s__, __--speaker__


Direct audio output to the speaker.


__-o h__, __--headphones__


Direct audio output to the headphone connector.


__-o l__, __--lineout__


Direct audio output to the line-out connector.


__-d__ ''n'', __--doublespeed__
''n''


Only play every ''n'''th frame. This will cause the MPEG
stream to be played ''n'' times faster, which can be used
for special effects. Can also be combined with the
__--halfspeed__ option to play 3 out of 4 frames etc.
Don't expect great sound quality when using this
option.


__-h__ ''n'', __--halfspeed__ ''n''


Play each frame ''n'' times. This will cause the MPEG
stream to be played at ''1''/''n'''th speed (n times
slower), which can be used for special effects. Can also be
combined with the __--doublespeed__ option to double
every third frame or things like that. Don't expect great
sound quality when using this option.


__-w__ ''file'', __--wav__


Write output as WAV file. This will cause the MPEG stream to
be decoded and saved as file ''file'' , or standard
output if ''-'' is used as file name. You can also use
''--au'' and ''--cdr'' for AU and CDR format,
respectively.


__-p__ ''URL'' | __none__, __--proxy__
''URL'' | __none__


The specified ''proxy'' will be used for HTTP requests.
It should be specified as full URL
(``http://host.domain:port/''), but the ``http://'' prefix,
the port number and the trailing slash are optional (the
default port is 80). Specifying __none__ means not to use
any proxy, and to retrieve files directly from the
respective servers. See also the ``HTTP SUPPORT''
section.


__-u__ ''auth'', __--auth__
''auth''


HTTP authentication to use when recieving files via HTTP.
The format used is user:password.


__-@__ ''file'', __--list__
''file''


Read filenames and/or URLs of MPEG audio streams from the
specified ''file'' in addition to the ones specified on
the command line (if any). Note that ''file'' can be
either an ordinary file, a dash ``-'' to indicate that a
list of filenames/URLs is to be read from the standard
input, or an URL pointing to a an appropriate list file.
Note: only one __-@__ option can be used (if more than
one is specified, only the last one will be
recognized).


__--au__ ''file''


Does not play the MPEG file but writes it to ''file'' in
SUN audio format. If - is used as the filename, the AU file
is written to stdout.


__--cdr__ ''file''


Does not play the MPEG file but writes it to ''file'' as
a CDR file. If - is used as the filename, the CDR file is
written to stdout.


__-z__, __--shuffle__


Shuffle play. Randomly shuffles the order of files specified
on the command line, or in the list file.


__-Z__, __--random__


Continuous random play. Keeps picking a random file from the
command line or the play list. Unlike shuffle play above,
random play never ends, and plays individual songs more than
once.


__--stereo__


Force stereo output


__--reopen__


Forces reopen of the audiodevice after ever
song


__--8bit__


Forces 8bit output


__-E__ ''file'', __--equalizer__


Enables equalization, taken from ''file''


__-T__, __--realtime__


Tries to gain realtime priority. This option usually
requires root privileges to have any effect.


__--aggressive__


Tries to get higher priority


__--title__


In an xterm, or rxvt, change the window's title to the name
of song currently playing.


__--help, --longhelp__


Shows usage instructions
!!OPERANDS
The following operands are supported:


''file''(s)


The path name(s) of one or more input files. They must be
valid MPEG-1/2 audio layer-1, -2 or -3 bit streams. If a
dash ``-'' is specified, MPEG data will be read from the
standard input. Furthermore, any name starting with
``http://'' is recognized as ''URL'' (see next
section).
!!HTTP SUPPORT


In addition to reading MPEG audio streams from ordinary
files and from the standard input, __mpg123__ supports
retrieval of MPEG audio files via the HTTP protocol, which
is used in the World Wide Web (WWW). Such files are
specified using a so-called URL (universal resource
location), which starts with ``http://''. When a file with
that prefix is encountered, __mpg123__ attempts to open
an HTTP connection to the server in order to retrieve that
file to decode and play it.


It is often useful to retrieve files through a WWW cache or
so-called proxy. To accomplish this, __mpg123__ examines
the environment for variables named __MP3_HTTP_PROXY__,
__http_proxy__ and __HTTP_PROXY__, in this order. The
value of the first one that is set will be used as proxy
specification. To override this, you can use the __-p__
command line option (see the ``OPTIONS'' section).
Specifying __-p none__ will enforce contacting the server
directly without using any proxy, even if one of the above
environment variables is set.


Note that, in order to play MPEG audio files from a WWW
server, it is necessary that the connection to that server
is fast enough. For example, a 128 kbit/s MPEG file requires
the network connection to be at least 128 kbit/s (16
kbyte/s) plus protocol overhead. If you suffer from short
network outages, you should try the __-b__ option
(buffer) to bypass such outages. If your network connection
is generally not fast enough to retrieve MPEG audio files in
realtime, you can first download the files to your local
harddisk (e.g. using lynx(1)) and then play them from
there.


If authentication is needed to access the file it can be
specified with the __-u user:pass__.
!!INTERRUPT


You can abort __mpg123__ at any time by pressing Ctrl-C.
If you are playing multiple files, this will stop the
current file and begin playing the next one. If you want to
abort playing immediately instead of skipping to the next
file, press Ctrl-C twice in short succession (within about
one second).


Note that the result of pressing Ctrl-C might not be audible
immediately, due to audio data buffering in the audio
device. This delay is system dependent, but it is usually
not more than one or two seconds.
!!SEE ALSO


lynx(1), sox(1), intro(1)
!!NOTES


MPEG audio decoding requires a good deal of CPU performance,
especially layer-3. To decode it in realtime, you should
have at least a Pentium, Alpha, SuperSparc or equivalent
processor. You can also use the __-singlemix__ option to
decode mono only, which reduces the CPU load somewhat for
layer-3 streams. See also the __-2__ and __-4__
options.


If everything else fails, use the __-s__ option to decode
to standard output, direct it into a file and then use an
appropriate utility to play that file. You might have to use
a tool such as sox(1) to convert the output to an
audio format suitable for your audio player.


Also note that __mpg123__ always generates 16 bit stereo
data (if one of the __-single__* options is used, two
identical stereo channels are generated). If your hardware
requires some other format, for example 8 bit mono, you also
have to use a converter such as sox(1).


If your system is generally fast enough to decode in
realtime, but there are sometimes periods of heavy system
load (such as cronjobs, users logging in remotely, starting
of ``big'' programs etc.) causing the audio output to be
interrupted, then you should use the __-b__ option to use
a buffer of at least 1000 Kbytes.
!!BUGS


Known bugs and limitations:


MPEG-2, Layer 1 and 2 not tested. May not work. (Layer 3
should work.)
Free format streams are not supported.
Layer-1 support is not heavily tested.
No CRC error checking is performed.
There is currently no support for audio hardware on DEC
Digital Unix, Ultrix and IBM AIX, therefore the __-s__
option has to be used on those platforms.
!!AUTHORS


Main author:


Michael Hipp


Uses code (or at least ideas) from:


MPEG Software Simulation Group (Base package)
Philipp Knirsch
Tobias Bading
Jeff Tsay
Thomas Woerner (SGI Audio)
Damien Clermonte
Oliver Fromme


Internet references:


http://www.mpg123.org
----
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