Manual Reference Pages  - mpg123 (1)


mpg123 - play audio MPEG 1.0/2.0/2.5 stream (layers 1, 2 and 3)


Input Options
Misc Options
Http Support


mpg123 [ options ] file ... | URL ... | -


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 audio bit stream.


The following operands are supported:
file(s) The path name(s) of one or more input files. They must be valid MPEG-1.0/2.0/2.5 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).


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 ‘‘--’’. Option arguments (if needed) follow separated by whitespace (not ‘‘=’’). Note that some options can be absent from your installation when disabled in the build process.


-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.
--fuzzy Enable fuzzy seeks (guessing byte offsets or using approximate seek points from Xing TOC). Without that, seeks need a first scan through the file before they can jump at positions. You can decide here: sample-accurate operation with gapless features or faster (fuzzy) seeking.
-y, --no-resync
  Do NOT try to resync and continue decoding if an error occurs in the input file. Normally, mpg123 tries to keep the playback alive at all costs, including skipping invalid material and searching new header when something goes wrong. With this switch you can make it bail out on data errors (and perhaps spare your ears a bad time). Note that this switch has been renamed from --resync. The old name still works, but is not advertised or recommened to use (subject to removal in future).
--resync-limit bytes
  Set number of bytes to search for valid MPEG data; <0 means search whole stream. If you know there are huge chunks of invalid data in your files... here is your hammer.
-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).
-l n, --listentry n
  Of the playlist, play specified entry only. n is the number of entry starting at 1. A value of 0 is the default and means playling the whole list, a negative value means showing of the list of titles with their numbers...
--loop times
  for looping track(s) a certain number of times, < 0 means infinite loop (not with --random!).
--keep-open For remote control mode: Keep loaded file open after reaching end.
--timeout seconds
  Timeout in (integer) seconds before declaring a stream dead (if <= 0, wait forever).
-z, --shuffle
  Shuffle play. Randomly shuffles the order of files specified on the command line, or in the list file.
-Z, --random
  Continuous random play. Keeps picking a random file from the command line or the play list. Unlike shuffle play above, random play never ends, and plays individual songs more than once.
--no-icy-meta Do not accept ICY meta data.
-i, --\index Index / scan through the track before playback. This fills the index table for seeking (if enabled in libmpg123) and may make the operating system cache the file contents for smoother operating on playback.
--index-size size
  Set the number of entries in the seek frame index table.
--preframes num
  Set the number of frames to be read as lead-in before a seeked-to position. This serves to fill the layer 3 bit reservoir, which is needed to faithfully reproduce a certain sample at a certain position. Note that for layer 3, a minimum of 1 is enforced (because of frame overlap), and for layer 1 and 2, this is limited to 2 (no bit reservoir in that case, but engine spin-up anyway).


-o module, --output module
  Select audio output module. You can provide a comma-separated list to use the first one that works.
  List the available modules.
-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.
-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 per default is raw (headerless) linear PCM audio data, 16 bit, stereo, host byte order (you can force mono or 8bit).
-O file, --outfile
  Write raw output into a file (instead of simply redirecting standard output to a file with the shell).
-w file, --wav
  Write output as WAV file. This will cause the MPEG stream to be decoded and saved as file file , or standard output if - is used as file name. You can also use --au and --cdr for AU and CDR format, respectively.
--au file Does not play the MPEG file but writes it to file in SUN audio format. If - is used as the filename, the AU file is written to stdout.
--cdr file Does not play the MPEG file but writes it to file as a CDR file. If - is used as the filename, the CDR file is written to stdout.
--reopen Forces reopen of the audiodevice after ever song
--cpu decoder-type
  Selects a certain decoder (optimized for specific CPU), for example i586 or MMX. The list of available decoders can vary; depending on the build and what your CPU supports. This options is only availabe when the build actually includes several optimized decoders.
--test-cpu Tests your CPU and prints a list of possible choices for --cpu.
--list-cpu Lists all available decoder choices, regardless of support by your CPU.
-g gain, --gain gain
  [DEPRECATED] Set audio hardware output gain (default: don’t change). The unit of the gain value is hardware and output module dependent. (This parameter is only provided for backwards compatibility and may be removed in the future without prior notice. Use the audio player for playing and a mixer app for mixing, UNIX style!)
-f factor, --scale factor
  Change scale factor (default: 32768).
--rva-mix, --rva-radio
  Enable RVA (relative volume adjustment) using the values stored for ReplayGain radio mode / mix mode with all tracks roughly equal loudness. The first valid information found in ID3V2 Tags (Comment named RVA or the RVA2 frame) or ReplayGain header in Lame/Info Tag is used.
--rva-album, --rva-audiophile
  Enable RVA (relative volume adjustment) using the values stored for ReplayGain audiophile mode / album mode with usually the effect of adjusting album loudness but keeping relative loudness inside album. The first valid information found in ID3V2 Tags (Comment named RVA_ALBUM or the RVA2 frame) or ReplayGain header in Lame/Info Tag is used.
-0, --single0; -1, --single1
  Decode only channel 0 (left) or channel 1 (right), respectively. These options are available for stereo MPEG streams only.
-m, --mono, --mix, --singlemix
  Mix both channels / decode mono. It takes less CPU time than full stereo decoding.
--stereo Force stereo output
-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.
-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.
--pitch value
  Set hardware pitch (speedup/down, 0 is neutral; 0.05 is 5%). This changes the output sampling rate, so it only works in the range your audio system/hardware supports.
--8bit Forces 8bit output
-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.
-E file, --equalizer
  Enables equalization, taken from file. The file needs to contain 32 lines of data, additional comment lines may be prefixed with #. Each data line consists of two floating-point entries, separated by whitespace. They specify the multipliers for left and right channel of a certain frequency band, respectively. The first line corresponds to the lowest, the 32nd to the highest frequency band. Note that you can control the equalizer interactively with the generic control interface.
--gapless Enable code that cuts (junk) samples at beginning and end of tracks, enabling gapless transitions between MPEG files when encoder padding and codec delays would prevent it. This is enabled per default beginning with mpg123 version 1.0.0 .
--no-gapless Disable the gapless code. That gives you MP3 decodings that include encoder delay and padding plus mpg123’s decoder delay.
-D n, --delay n
  Insert a delay of n seconds before each track.
-o h, --headphones
  Direct audio output to the headphone connector (some hardware only; AIX, HP, SUN).
-o s, --speaker
  Direct audio output to the speaker (some hardware only; AIX, HP, SUN).
-o l, --lineout
  Direct audio output to the line-out connector (some hardware only; AIX, HP, SUN).
-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.
--preload fraction
  Wait for the buffer to be filled to fraction before starting playback (fraction between 0 and 1). You can tune this prebuffering to either get faster sound to your ears or safer uninterrupted web radio. Default is 1 (wait for full buffer before playback).
--smooth Keep buffer over track boundaries -- meaning, do not empty the buffer between tracks for possibly some added smoothness.


-t, --test Test mode. The audio stream is decoded, but no output occurs.
-c, --check Check for filter range violations (clipping), 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.
-C, --control
  Enable terminal control keys. By default use ’s’ or the space bar to stop/restart (pause, unpause) playback, ’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. Type ’h’ for a full list of available controls.
--title In an xterm, or rxvt (compatible, TERM environment variable is examined), change the window’s title to the name of song currently playing.
--long-tag Display ID3 tag info always in long format with one line per item (artist, title, ...)
--utf8 Regardless of environment, print metadata in UTF-8 (otherwise, when not using UTF-8 locale, you’ll get ASCII stripdown).
-R, --remote
  Activate generic control interface. mpg123 will then read and execute commands from stdin. Basic usage is ‘‘load <filename> ’’ to play some file and the obvious ‘‘pause’’, ‘‘command. ‘‘jump <frame>’’ will jump/seek to a given point (MPEG frame number). Issue ‘‘help’’ to get a full list of commands and syntax.
--remote-err Print responses for generic control mode to standard error, not standard out. This is automatically triggered when using -s .
--fifo path
  Create a fifo / named pipe on the given path and use that for reading commands instead of standard input.
  Tries to get higher priority
-T, --realtime
  Tries to gain realtime priority. This option usually requires root privileges to have any effect.
-?, --help Shows short usage instructions.
--longhelp Shows long usage instructions.
--version Print the version string.


In addition to reading MPEG audio streams from ordinary files and from the standard input, mpg123 supports retrieval of MPEG audio files or playlists via the HTTP protocol, which is used in the World Wide Web (WWW). Such files are specified using a so-called URL, 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 wget(1)) and then play them from there.

If authentication is needed to access the file it can be specified with the -u user:pass.


When in terminal control mode, you can quit via pressing the q key, while any time you can abort mpg123 by pressing Ctrl-C. If not in terminal control mode, this will skip to the next file (if any). If you want to abort playing immediately in that case, press Ctrl-C twice in short succession (within about one second).

Note that the result of quitting mpg123 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.


wget(1), sox(1),


MPEG audio decoding requires a good deal of CPU performance, especially layer-3. To decode it in realtime, you should have at least an i486DX4, Pentium, Alpha, SuperSparc or equivalent processor. You can also use the -m 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.

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 reasonable size (at least 1000 Kbytes).


Mostly MPEG-1 layer 2 and 3 are tested in real life. Please report any issues and provide test files to help fixing them.

Free format streams are not supported, but they could be (there is some code).

No CRC error checking is performed.

Some platforms lack audio hardware support; you may be able to use the -s switch to feed the decoded data to a program that can play it on your audio device. Notably, this includes Tru64 with MME, but you should be able to install and use OSS there (it perhaps will perform better as MME would anyway).


  Thomas Orgis <>, <>
Nicholas J. Humfrey
  Michael Hipp
Uses code or ideas from various people, see the AUTHORS file accompanying the source code.


mpg123 is licensed under the GNU Lesser/Library General Public License, LGPL, version 2.1 .


mpg123 (1) 31 Jan 2008
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