mpg123(1)mpg123(1)NAMEmpg123 - play audio MPEG 1.0/2.0 file (layers 1, 2 and 3)
SYNOPSISmpg123 [ -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 ... | -
DESCRIPTIONmpg123 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.
OPTIONSmpg123 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.
-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.
21 Apr 1997 1
mpg123(1)mpg123(1)-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 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 bitrate inde
pended of the mpeg stream rate. mpg123 automagi
cally 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.
21 Apr 1997 2
mpg123(1)mpg123(1)-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.
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mpg123(1)mpg123(1)--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. 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.
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mpg123(1)mpg123(1)
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.
SEE ALSOlynx(1), sox(1), intro(1)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.
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mpg123(1)mpg123(1)
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.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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