.\"
.\" madplay - MPEG audio decoder and player
.\" Copyright (C) 2000-2004 Robert Leslie
.\"
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.\" GNU General Public License for more details.
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.\" Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
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.\" $Id$
.\"
.TH MADPLAY 1 "22 February 2004" "MAD" "MPEG Audio Decoder"
.SH NAME
madplay \- decode and play MPEG audio stream(s)
.SH SYNOPSIS
.B madplay
.RI [ options ]
.I file
\&...
.br
.B madplay
.RI [ options ]
\fB\-o\fR [\fItype\fB:\fR]\fIpath\fR
.I file
\&...
.SH DESCRIPTION
.B madplay
is a command-line MPEG audio decoder and player based on the MAD library
.RI ( libmad ).
.PP
MAD is a high-quality MPEG audio decoder. It currently supports MPEG-1 and the
MPEG-2 extension to Lower Sampling Frequencies, as well as the so-called
MPEG\ 2.5 format. All three audio layers (Layer\ I, Layer\ II, and Layer\ III
a.k.a. MP3) are fully implemented.
.PP
Among the special features of MAD are 24-bit PCM resolution and 100%
fixed-point (integer) computation. Since MAD is implemented entirely without
the use of floating point arithmetic, it performs especially well on
architectures without an FPU.
.PP
MAD does not yet support MPEG-2 multichannel audio (although it should be
backward compatible with such streams) nor does it currently support AAC.
.PP
By default
.B madplay
reads and decodes one or more input
.IR file s
containing MPEG audio data and plays them on the native audio device. If the
input file is a single dash (\-), data is read from standard input.
.PP
Decoded output may optionally be redirected to a file instead of being played
on the audio device by using the
.B \-o
.RB ( \-\-output )
option.
.PP
For each
.IR file ,
.B madplay
will also attempt to read and display ID3 tag information. The supported tag
versions are ID3v1, ID3v1.1, ID3v2.2, ID3v2.3, and ID3v2.4. If a tag contains
relative volume adjustment information (RVA2),
.B madplay
will use the information to adjust the master volume for output. This behavior
can be changed with the
.B \-A
.RB ( \-\-adjust\-volume )
and
.B \-G
.RB ( \-\-replay\-gain )
options.
.PP
If the
.B \-T
.RB ( \-\-show\-tags\-only )
option is used, decoding is not performed but tag information is still
displayed. When used in conjunction with
.B \-v
.RB ( \-\-verbose ),
encoder as well as ID3 tags are shown.
.SH OPTIONS
.SS Verbosity
.TP
.BR \-v " or " \-\-verbose
Generally show more information than the default. During decoding, show
information about the stream including playing time, audio layer, bit rate,
sampling frequency, and stereo mode.
.TP
.BR \-q " or " \-\-quiet
Generally show less information than the default. Do not show any information
during decoding except warnings.
.TP
.BR \-Q " or " \-\-very\-quiet
Generally show no information except severe errors. Do not show any
information or warnings during decoding.
.TP
.BI \-\-display\-time= mode
Set the default verbose time display mode to
.IR mode ,
which must be one of
.BR remaining ,
.BR current ,
or
.BR overall .
This is only relevant with
.B -v
.RB ( \-\-verbose ).
See
.B \-\-tty\-control
below for details on changing the time display mode during playback.
.SS Decoding
.TP
.B \-\-downsample
Reduce the decoded sampling frequency 2:1. This also reduces the computational
overhead of the decoder.
.TP
.BR \-i " or " \-\-ignore\-crc
Ignore CRC information in the audio stream. This causes frames with CRC errors
to be decoded and played anyway. This option is not recommended, but since
some encoders have been known to generate bad CRC information, this option is
a work-around to play streams from such encoders.
.TP
\fB\-\-ancillary\-output=\fIpath\fR
Write ancillary data from the MPEG audio stream to
.IR path .
If
.I path
is a single dash (\-), the data will be written to standard output.
Bits from the ancillary data stream are packed into octets; if any bits
remain, the final octet will be padded with zero bits. See the
.B NOTES
section below for further information about this option.
.SS Audio Output
.TP
\fB\-o\fR or \fB\-\-output=\fR[\fItype\fB:\fR]\fIpath\fR
Direct output to
.IR path ,
rather than playing audio on the native audio device. The format of the output
is specified by
.I type
which can be any of the supported output formats (see
.B Output Formats
below.) If a format is not specified, one will be inferred from
.IR path .
If
.I path
is a single dash (\-), the output will be written to standard output.
.TP
\fB\-b\fR or \fB\-\-bit\-depth=\fIdepth\fR
Request an output precision of
.I depth
bits per sample. Higher bit depths yield higher quality sound. Typical bit
depths are 8, 16, 24, and 32, however other depths may also be possible.
Whether the request can be honored depends on the capabilities of the audio
device or output format.
See the
.B NOTES
section below for further details about this option.
.TP
\fB\-R\fR or \fB\-\-sample\-rate=\fIhertz\fR
Request an output sampling frequency of
.I hertz
samples per second (Hz).
The sample rate must be in the range 1000 to 65535\ Hz.
Whether the request can be honored depends on the capabilities of the audio
device or output format.
If the effective rate is not the same as the rate of the decoded audio, output
may be resampled, possibly resulting in lower quality sound.
.TP
.BR \-d " or " \-\-no\-dither
Do not dither output PCM samples. This may result in lower quality sound but
is useful for analyzing output from the decoder.
.TP
\fB\-\-fade\-in\fR[\fB=\fIduration\fR]
Gradually fade-in the audio from each file over
.IR duration .
If not specified, the default duration is
.B 0:05
(five seconds.)
.TP
\fB\-a\fR or \fB\-\-attenuate=\fIdecibels\fR or \fB\-\-amplify=\fIdecibels\fR
Attenuate or amplify the signal by
.I decibels
(dB).
The signal is attenuated if the decibel value is negative; it is amplified if
the value is positive.
The value must be in the range \-175 to +18\ dB.
The value may be fractional, e.g. \-1.5\ dB.
A value of 0\ dB will leave the signal unchanged.
Each step of 6\ dB will approximately halve (in the negative direction) or
double (in the positive direction) the strength of the signal.
.TP
\fB\-A\fR or \fB\-\-adjust\-volume=\fIdecibels\fR
Adjust the relative volume for all files. This option overrides any per-file
volume adjustment settings. For example,
.B \-A0
may be used to ignore relative volume adjustments given by ID3 tags. Relative
volume adjustments specified by this option or by ID3 tags are used as the
base volume against which the signal is further attenuated or amplified using
the
.B \-a
.RB ( \-\-attenuate ,
.BR \-\-amplify )
option or keyboard controls.
This option cannot be used together with
.B \-G
.RB ( \-\-replay\-gain ).
.TP
\fB\-G\fR or \fB\-\-replay\-gain\fR[\fB=\fIprofile\fR]
Enable Replay Gain volume adjustments. Replay Gain information contained in
the decoded files (if any) is used to make volume adjustments for output. The
.I profile
may be one of
.B radio
(the default) or
.BR audiophile .
See the
.B NOTES
section below for further details. When Replay Gain is enabled, a default
pre-amp gain of +6\ dB is also applied; this can be changed with the
.B \-a
.RB ( \-\-attenuate ,
.BR \-\-amplify )
option.
.SS Channel Selection
.PP
For dual channel streams, an output channel should be selected. If one is not
selected, the first (left) channel will be used.
.PP
For stereo streams, making a channel selection other than stereo will cause
the output to become monaural.
.TP
.BR \-1 " or " \-\-left
Output the first (left) channel only.
.TP
.BR \-2 " or " \-\-right
Output the second (right) channel only.
.TP
.BR \-m " or " \-\-mono
Mix the left and right channels together.
.TP
.BR \-S " or " \-\-stereo
Force stereo output, even if the stream is single or dual channel.
.SS Playback
.TP
\fB\-s\fR or \fB\-\-start=\fItime\fR
Begin playing at
.IR time ,
given as an offset from the beginning of the first file
.RB ( 0:00:00 ),
seeking as necessary.
.TP
\fB\-t\fR or \fB\-\-time=\fIduration\fR
Stop playback after the playing time of the output audio equals
.IR duration .
.TP
.BR \-z " or " \-\-shuffle
Randomize the list of files given on the command line for playback.
.TP
\fB\-r\fR or \fB\-\-repeat\fR[\fB=\fImax\fR]
Play the input files
.I max
times, or indefinitely. Playback can be stopped prematurely by giving a time
limit with the
.B \-t
.RB ( \-\-time )
option. If
.B \-z
.RB ( \-\-shuffle )
is also used, the files will be continuously shuffled and repeated in such a
way that the same file is not played again until at least half of the other
files have played in the interim.
.TP
.B \-\-tty\-control
Enable keyboard controls during playback. This is the default unless standard
input is not a terminal, output is redirected with
.B \-o
.RB ( \-\-output ),
or either of
.B \-q
.RB ( \-\-quiet )
or
.B \-Q
.RB ( \-\-very\-quiet )
is given.
The keyboard controls are:
.RS
.TP 3
.B P
Pause; press any key to resume.
.TP 3
.B S
Stop; press any key to replay the current file from the beginning.
.TP 3
.B F
Forward; advance to the next file.
.TP 3
.B B
Back; replay the current file, unless it has been playing for less than 4
seconds, in which case replay the previous file.
.TP 3
.B T
Time display; change the time display mode. This only works with
.B \-v
.RB ( \-\-verbose ).
The display mode alternates among overall playing time, current time
remaining, and current playing time.
.TP 3
.B +
Increase gain; increase the audio output gain by 0.5\ dB.
.TP 3
.B \-
Decrease gain; decrease the audio output gain by 0.5\ dB.
.TP 3
.B Q
Quit; stop decoding and exit.
.RE
.TP
.B \-\-no\-tty\-control
Disable keyboard controls during playback. This is the default when standard
input is not a terminal, output is redirected with
.B \-o
.RB ( \-\-output ),
or either of
.B \-q
.RB ( \-\-quiet )
or
.B \-Q
.RB ( \-\-very\-quiet )
is given.
.SS Miscellaneous
.TP
.BR \-T " or " \-\-show\-tags\-only
Show ID3 and/or encoder tags from the input
.IR file s
but do not otherwise decode or play any audio. By default only ID3 tags are
shown (if any). With
.B \-v
.RB ( \-\-verbose ),
all tags are shown. Encoder tags recognized by
.B madplay
include the Xing VBR header tag and the header tag format written by
.BR lame (1).
.TP
.BR \-V " or " \-\-version
Display the effective version and build options for
.B madplay
and exit.
.TP
.B \-\-license
Display copyright, license, and warranty information and exit.
.TP
.BR \-h " or " \-\-help
Display usage information and exit.
.SH Output Formats
Other than playing on the native audio device, the following output formats
are supported:
.TP
.B cdda
CD audio, 16-bit big-endian 44100\ Hz stereo PCM, padded to 2352-byte block
boundary
.RB ( *.cdr ,
.BR *.cda )
.TP
.B aiff
Audio IFF, [16-bit] PCM
.RB ( *.aif ,
.BR *.aiff )
.TP
.B wave
Microsoft RIFF/WAVE, [16-bit] PCM
.RB ( *.wav )
.TP
.B snd
Sun/NeXT audio, 8-bit ISDN \(*m-law
.RB ( *.au ,
.BR *.snd )
.TP
.B raw
binary [16-bit] host-endian linear PCM, stereo interleaved
.TP
.B hex
ASCII hexadecimal [24-bit] linear PCM, stereo interleaved, one sample per
output line
.TP
.B esd
Enlightened Sound Daemon (EsounD) [16-bit] (give speaker host as
.IR path )
.TP
.B null
no output (usually for testing or timing the decoder)
.PP
Default bit depths shown in square brackets can be changed with the
.B \-b
.RB ( \-\-bit\-depth )
option.
.PP
Note that EsounD support requires the
.I libesd
library.
.SH Time Specifications
For options which accept a time or duration argument, the following time
specifications are recognized:
.TP
.IB hh : mm : ss . ddd
Hours, minutes, seconds, and decimal fractions of a second. This specification
is flexible;
.IB hh : mm : ss\c
,
.IB mmm : ss\c
,
.BI : ss\c
,
.IB sss . ddd\c
,
.BI . ddd\c
, and
.I ssss
are all acceptable. The component values are not constrained to any particular
range or number of digits.
.TP
.IB frac / unit
A length of time specified as a rational number, in seconds. This can be used
for sample-granularity, for example
.B 32/44100
for 32 samples, assuming a 44100\ Hz sample frequency.
.TP
.IB time1 + time2
A composite time made by adding two time values together. This permits mixing
the above specification forms.
.PP
The resolution of any time value cannot exceed 1/352800000 seconds.
.SH DIAGNOSTICS
.TP
.B error: frame #: lost synchronization
If encountered at the beginning of a file, this means the file contains
something other than an ID3v2 tag before the MPEG audio data. If encountered
in the middle of a file, it may mean the file is corrupt. This message is most
commonly encountered, however, at the end of a file if the file contains an
ID3v1 tag that is not aligned to an MPEG audio frame boundary. In this case,
the message is harmless and may be ignored.
.PP
.TP
.B error: frame #: bad main_data_begin pointer
This message can occur while decoding a Layer\ III stream that has been cut or
spliced without preserving its bit reservoir. The affected frame cannot be
properly decoded, but will be used to help restore the bit reservoir for
following frames.
.PP
Most other messages indicate a deficiency in the input stream.
.PP
When a frame cannot be properly decoded, a concealment strategy is used as
follows:
.TP 2
\(bu
If the previous frame was properly decoded, it is repeated in place of the
current frame.
.TP 2
\(bu
If the previous frame was
.I not
properly decoded, the current frame is muted.
.SH NOTES
.SS Output Precision
Because MAD produces samples with a precision greater than 24 bits, by default
.B madplay
will dither the samples to the precision of the output format. This produces
high quality audio that generally sounds superior to the output of a simple
rounding algorithm. However, dithering may unfavorably affect an analytic
examination of the output, and therefore it may be disabled by using the
.B \-d
.RB ( \-\-no\-dither )
option.
.PP
The actual precision of output samples can be requested with the
.B \-b
.RB ( \-\-bit\-depth )
option. Whether the request can be honored depends on the capabilities of the
audio device or output format. If this option is not specified, a typical
default depth will be used (often 16) or in the case of output to an audio
device, the highest bit depth determined to work reliably with the device will
be used.
.PP
Note that bit depths greater than 24 are effectively the same as 24-bit
precision samples padded to the requested depth.
.SS Ancillary Data
MPEG audio streams contain an ancillary data stream in addition to audio data.
Most often this does not contain any useful information and may simply consist
of padding bits. The MPEG-2 extension to multichannel audio uses part of this
ancillary stream to convey multichannel information; presently MAD does not
interpret such data.
.PP
For applications which have uses for the stream, ancillary data can be
extracted with the
.B \-\-ancillary\-output
option.
.SS Replay Gain
.B madplay
optionally supports the Replay Gain proposed standard with the
.B \-G
.RB ( \-\-replay\-gain )
option to make compensating volume adjustments when playing decoded audio from
different sources. There are two Replay Gain profiles:
.B radio
strives to make gain adjustments that give all tracks equal loudness, while
.B audiophile
attempts to give ideal listening loudness. These adjustments are relative to a
reference of 83\ dB SPL.
.PP
A pre-amp gain is also used in conjunction with Replay Gain to achieve the
overall desired loudness. When Replay Gain is enabled, this pre-amp gain
defaults to +6\ dB, however it can be changed with the
.B \-a
.RB ( \-\-attenuate ,
.BR \-\-amplify )
option or keyboard controls.
.PP
Note that when enabled, Replay Gain overrides any relative volume adjustments
specified by ID3 tags (RVA2). Replay Gain is also incompatible with the
.B \-A
.RB ( \-\-adjust\-volume )
option; any attempt to use it will be ignored.
.PP
Replay Gain information is read either from an ID3 tag (RGAD) or from an
encoder tag written by
.BR lame (1).
If both are present, the information in the ID3 tag takes precedence. In
accordance with the proposed standard, if the requested Replay Gain profile is
not available but the alternate is, the alternate is used instead.
.PP
Due to an unfortunate heresy, versions of
.BR lame (1)
since 3.95.1 write Replay Gain information using a reference of 89\ dB SPL
instead of the 83\ dB specified in the Replay Gain proposed standard. To
compensate,
.B madplay
automatically subtracts 6\ dB from the Replay Gain values read from such tags.
.PP
Note that
.B madplay
does not yet support hard limiting as suggested by the Replay Gain proposed
standard; nor does it automatically reduce the pre-amp gain to avoid clipping.
.SH CONFORMING TO
MAD conforms to Part\ 3 of the ISO/IEC\ 11172 (MPEG-1) international standard
for decoding MPEG audio. In addition, MAD supports the extension to Lower
Sampling Frequencies (LSF) as defined in Part\ 3 of ISO/IEC\ 13818 (MPEG-2).
.PP
The output from MAD has been tested and found to satisfy the ISO/IEC\ 11172-4
computational accuracy requirements for compliance. In most configurations,
MAD is a
.I Full Layer\ III ISO/IEC\ 11172-3 audio decoder
as defined by the standard.
.PP
The ID3 tag parsing library used by
.B madplay
conforms to the ID3v2.4.0 informal standard.
.PP
With the exception of the clipping prevention provisions, Replay Gain support
provided by
.B madplay
is in accordance with the Replay Gain proposed standard published on July\ 10,
2001 by David Robinson.
.SH BUGS
The resampling algorithm used by
.B madplay
is one of a linear interpolation, and does not produce optimum quality
sound.
.PP
The granularity of start and stop times
.RB ( \-\-start
and
.BR \-\-time )
is not yet as fine as this document suggests.
.SH AUTHOR
Robert Leslie <rob@mars.org>
.SH SEE ALSO
.BR lame (1),
.BR normalize (1),
.BR sox (1),
.BR wget (1)
.\" .BR id3tag (1)
.\" .BR libmad (3)
.\" .BR libid3tag (3)