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, 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. 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 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 output rate independed of
the mpeg stream rate. mpg123 automagically 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 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
-w, --wavfile
Write the song using the WAV format to the specified
file
Instead of a real filename you can use a dash ``-'' to indicate that
the data is to be written 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. 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.
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.
