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.\" @(#)mpg123.1 0.01 21-Apr-1997 OF; from mpg123 archive

.TH mpg123 1 "21 Apr 1997"

.SH NAME

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

.SH SYNOPSIS

.B mpg123

[

.B \-tscvqy01m24

]

[

.BI \-b " size"

]

[

.BI \-k " num"

]

[

.BI \-n " num"

]

[

.BI \-f " factor"

]

[

.BI \-r " rate"

]

[

.BI \-g " gain"

]

[

.BI \-a " dev"

]

[

.BR "\-o s" " | " "\-o h" " | " "\-o l"

]

[

.BI \-d " n"

]

[

.BI \-h " n"

]

[

.BI \-p " proxy"

]

[

.BI \-@ " file"

]

.IR file " ... | " URL " ... | "

.B \-

.SH DESCRIPTION

.B mpg123

reads one or more

.IR file\^ s

(or standard input if ``\-'' is specified) or

.IR URL\^ s

and plays them on the audio device (default) or

outputs them to stdout.

.IR file\^ / URL

is assumed to be an MPEG-1/2 audio bit stream.

.SH OPTIONS

.B 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 ``\-\^\-''.

.TP

.BR \-t ", " \-\^\-test

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

.TP

.BR \-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

.BR mpg123 .

The output format is raw (headerless) linear PCM audio data,

16 bit, stereo, host byte order.

.TP

.BR \-c ", " \-\^\-check

Check for filter range violations, and report them for each frame

if any occur.

.TP

.BR \-v ", " \-\^\-verbose

Increase the verbosity level.  For example, displays the frame

numbers during decoding.

.TP

.BR \-q ", " \-\^\-quiet

Quiet.  Suppress diagnostic messages.

.TP

.BR \-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

.B 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.

.TP

.BR \-0 ", " \-\^\-single0 "; " \-1 ", " \-\^\-single1

Decode only channel 0 (left) or channel 1 (right),

respectively.  These options are available for

stereo MPEG streams only.

.TP

.BR \-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.

.TP

.BR \-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.

.TP

\fB\-b \fIsize\fR, \fB\-\^\-buffer \fIsize

Use an audio output buffer of

.I 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.

.TP

\fB\-k \fInum\fR, \fB\-\^\-skip \fInum

Skip first

.I num

frames.  By default the decoding starts at the first frame.

.TP

\fB\-n \fInum\fR, \fB\-\^\-frames \fInum

Decode only

.I num

frames.  By default the complete stream is decoded.

.TP

\fB\-f \fIfactor\fR, \fB\-\^\-scale \fIfactor

Change scale factor (default: 32768).

.TP

\fB\-r \fIrate\fR, \fB\-\^\-rate \fIrate

Set sample rate (default: automatic).  You don't want to

change this.

.TP

\fB\-g \fIgain\fR, \fB\-\^\-gain \fIgain

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

.TP

\fB\-a \fIdev\fR, \fB\-\^\-audiodevice \fIdev

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.

.TP

.BR "\-o s" ", " \-\^\-speaker

Direct audio output to the speaker.

.TP

.BR "\-o h" ", " \-\^\-headphones

Direct audio output to the headphone connector.

.TP

.BR "\-o l" ", " \-\^\-lineout

Direct audio output to the line-out connector.

.TP

\fB\-d \fIn\fR, \fB\-\^\-doublespeed \fIn

Only play every

.IR n 'th

frame.  This will cause the MPEG stream

to be played

.I n

times faster, which can be used for special

effects.  Can also be combined with the

.B \-\^\-halfspeed

option to play 3 out of 4 frames etc.  Don't expect great

sound quality when using this option.

.TP

\fB\-h \fIn\fR, \fB\-\^\-halfspeed \fIn

Play each frame

.I n

times.  This will cause the MPEG stream

to be played at

.RI 1 / n 'th

speed (n times slower), which can be

used for special effects. Can also be combined with the

.B \-\^\-doublespeed

option to double every third frame or things like that.

Don't expect great sound quality when using this option.

.TP

\fB\-p \fIURL \fR| \fBnone\fR, \fB\-\^\-proxy \fIURL \fR| \fBnone

The specified

.I 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

.B none

means not to use any proxy, and to retrieve files directly

from the respective servers.  See also the

``HTTP SUPPORT'' section.

.TP

\fB\-@ \fIfile\fR, \fB\-\^\-list \fIfile

Read filenames and/or URLs of MPEG audio streams from the specified

.I file

in addition to the ones specified on the command line (if any).

Note that

.I 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

.B \-@

option can be used (if more than one is specified, only the

last one will be recognized).

.SH OPERANDS

The following operands are supported:

.TP 8

.IR 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

.I URL

(see next section).

.SH HTTP SUPPORT

In addition to reading MPEG audio streams from ordinary

files and from the standard input,

.B 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,

.B mpg123

attempts to open an HTTP connection to the server in order to

retrieve that file to decode and play it.

.P

It is often useful to retrieve files through a WWW cache or

so-called proxy.  To accomplish this,

.B mpg123

examines the environment for variables named

.BR 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

.B \-p

command line option (see the ``OPTIONS'' section).  Specifying

.B "\-p none"

will enforce contacting the server directly without using

any proxy, even if one of the above environment variables

is set.

.P

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 \-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

.BR lynx (1))

and then play them from there.

.SH INTERRUPT

You can abort

.B 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).

.P

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.

.SH "SEE ALSO"

.BR lynx (1),

.BR sox (1),

.BR intro (1)

.SH 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

.B -singlemix

option to decode mono only, which reduces the CPU load

somewhat for layer-3 streams.  See also the

.BR \-2 " and " \-4

options.

.P

If everything else fails, use the

.B \-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

.BR sox (1)

to convert the output to an audio format suitable for

your audio player.

.P

Also note that

.B mpg123

always generates 16 bit stereo data (if one of the

.BR \-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

.BR sox (1).

.P

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 \-b

option to use a buffer of at least 1000 Kbytes.

.SH BUGS

.TP

Known bugs and limitations:

.br

MPEG-2, Layer 1 and 2 not tested. May not work. (Layer 3 should work.)

.br

Free format streams are not supported.

.br

Layer-1 support is not heavily tested.

.br

No CRC error checking is performed.

.br

There is currently no support for audio hardware on

DEC Digital Unix, Ultrix and IBM AIX, therefore the

.B \-s

option has to be used on those platforms.

.SH AUTHORS

.TP

Main author:

.br

Michael Hipp <Michael.Hipp@student.uni-tuebingen.de>

.TP

Uses code (or at least ideas) from:

.br

MPEG Software Simulation Group (Base package)

.br

Philipp Knirsch <phil@mpik-tueb.mpg.de> (DCT36/manual unroll)

.br

Tobias Bading <bading@cs.tu-berlin.de> (subband synthesis)

.br

Jeff Tsay <ctsay@pasteur.eecs.berkeley.edu> (DCT36)

.br

Thomas Woerner (SGI Audio)

.br

Damien Clermonte <clermond@esiee.fr> (HP-UX audio fixes)

.br

Oliver Fromme <oliver.fromme@heim3.tu-clausthal.de>

.P

Internet references:

.br

http://www.sfs.nphil.uni-tuebingen.de/~hipp/mpg123.html

.br

http://www.heim3.tu-clausthal.de/~olli/mpg123/

.br

(includes information about the mpg123 mailing list)

.P

The latest version is also available from here:

.br

ftp.tu-clausthal.de:/pub/unix/audio/mpg123

.br

http://ftp.tu-clausthal.de/pub/unix/audio/mpg123