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NAME
mpg123 - play audio MPEG 1.0/2.0 file (layers 1, 2 and 3)
SYNOPSIS
mpg123 [ -tscvqy01m24 ] [ -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 ] [ -@ 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 out-
put, 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 (header-
less) 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.
-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,
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,
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 buffer-
ing 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 com-
bined 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 stan-
dard 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 recog-
nized).
-z, --shuffle
Shuffle play. Randomly shuffles the files specified 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
-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. 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 encoun-
tered, 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 over-
ride this, you can use the -p command line option (see the
``OPTIONS'' section). Specifying -p none will enforce con-
tacting 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 gen-
erally 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 play-
ing 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 dev-
ice. 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 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 inter-
rupted, 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/manual
unroll)
Tobias Bading <bading@cs.tu-berlin.de> (subband syn-
thesis)
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.sfs.nphil.uni-tuebingen.de/~hipp/mpg123.html
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
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