mpg123(1)

NAME

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

SYNOPSIS

mpg123 [ -tscCvqy01m24 ] [ -b size ] [ -k num ] [ -n num ]
[ -f factor ] [ -r rate ] [ -g gain ] [ -a dev ] [ -o s
-o h | -o l ] [ -d n ] [ -h n ] [ -p proxy ] [ -u u ] [ -@
file ] file ... | URL ... |

DESCRIPTION

mpg123 reads one or more files (or standard input if ``-'' is specified) or URLs 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, dis
plays 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 bro
ken MPEG file, on which mpg123 normally gives up saying `Illegal header'. Be careful: Broken loca
tions 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. Please note, that does not change
speed of the song. Ie the --2to1 option is the same
like forcing the sampling output rate to -r 22050
on a 44.1 kHz song.
-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 out
put 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 output rate
independed of the mpeg stream rate. mpg123 automag
ically converts the rate (down/up sampling) . 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.
-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).
-z, --shuffle: Shuffle play. Randomly shuffles the files speci
fied on the command line and in the list file.
--stereo: Force stereo output
--reopen: Forces reopen of the audiodevice after ever song
--8bit Forces 8bit output
-w, --wav file: Write the song using the WAV format to the speci
fied file Instead of a real filename you can use a
dash ``-'' to indicate that the data is to be writ
ten to standard out.
-Z, --random: Full random play

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. Further
more, any name starting with ``http://'' is recog
nized 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 spec
ified using a so-called URL (universal resource location),
which starts with ``http://''. When a file with that pre
fix is encountered, mpg123 attempts to open an HTTP con
nection 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 specifica
tion. 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 connec
tion 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 audi
ble 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.

NOTES

MPEG audio decoding requires a good deal of CPU perfor
mance, 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 real
time, 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 <hippm@informatik.uni-tuebingen.de>
Uses code (or at least ideas) from:: MPEG Software Simulation Group (Base package)
Philipp Knirsch <phil@mpik-tueb.mpg.de> (DCT36/man
ual unroll)
Tobias Bading <bading@cs.tu-berlin.de> (subband
synthesis)
Jeff Tsay <ctsay@pasteur.eecs.berkeley.edu> (DCT36)
Thomas Woerner (SGI Audio)
Damien Clermonte <clermond@esiee.fr> (HP-UX audio
fixes)
Oliver Fromme <oliver.fromme@heim3.tu-clausthal.de>
Internet references: http://www.mpg123.de/ http://www.heim3.tu-clausthal.de/~olli/mpg123/ (includes information about the mpg123 mailing list)
The latest version is also available from here: ftp.tu-clausthal.de:/pub/unix/audio/mpg123 http://ftp.tu-clausthal.de/pub/unix/audio/mpg123

docs.sk

comprehensive documentation repository

See also