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.\"                                      Hey, EMACS: -*- nroff -*-
.\" (C) Copyright 2013 Chris Boot <debian@bootc.net>
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.\" other parameters are allowed: see man(7), man(1)
.TH SQUEEZELITE 1 "November 24, 2013" "Debian Project"
.\" Please adjust this date whenever revising the manpage.
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.SH NAME
squeezelite \- Lightweight headless Squeezebox emulator
.SH SYNOPSIS
.B squeezelite
.RI [ options ]
.SH DESCRIPTION
.B Squeezelite
is a small headless Logitech Squeezebox emulator. It is aimed at supporting high
quality audio including USB DAC based output at multiple sample rates.
.PP
The player is controlled using, and media is streamed from, a Logitech Media
Server instance running somewhere on the local network.
.SH OPTIONS
This program supports the following options:
.TP
.B \-h
Show a summary of the available command-line options.
.TP
.B \-s <server>[:<port>]
Connect to the specified Logitech Media Server, otherwise uses automatic
discovery to find server on the local network. This option should only be needed
if automatic discovery does not work, or the server is not on the local network
segment (e.g. behind a router).
.TP
.B \-o <output device>
Specify the audio output device; the default value is 
.IR default .
Use the
.B \-l
option to list available output devices.
.TP
.B \-l
List available audio output devices to stdout and exit. These device names can
be passed to the
.B \-o
option in order to select a particular device or configuration to use for audio
playback.
.TP
.B \-a <b>:<p>:<f>:<m>
Specify ALSA parameters used when opening an audio output device.
.B <b>
is the buffer time in milliseconds (values less than 500) or size in bytes (default
.IR 40 ms);
.B <p>
is the period count (values less than 50) or size in bytes (default
.IR 4 " periods);"
.B <f>
is the sample format (possible values:
.IR 16 ", " 24 ", " 24_3 " or " 32 );
.B <m>
is whether to use mmap (possible values:
.IR 0 " or " 1 ).
.TP
.B \-b <stream>:<output>
Specify internal stream and output buffer sizes in kilobytes.
.TP
.B \-c <codec1>,...
Restrict codecs to those specified, otherwise load all available codecs; known codecs:
.IR flac ", " pcm ", " mp3 ", " ogg ", " aac ", " wma ", " alac .
.IR mad " or " mpg
can be supplied instead of
.I mp3
to use a specific decoder library.
.TP
.B \-d <category>=<level>
Set logging level. Categories are:
.IR all ", " slimproto ", " stream ", " decode " or " output .
Levels can be:
.IR info ", " debug " or " sdebug .
The option can be repeated to set different log levels for different categories.
.TP
.B \-f <logfile>
Send logging output to a log file instead of standard output or standard error.
.TP
.B \-m <mac addr>
Override the player's MAC address. The format must be colon-delimited
hexadecimal, for example: ab:cd:ef:12:34:56. This is usually automatically
detected, and should not need to be provided in most circumstances.
.TP
.B \-n <name>
Set the player name. This name is used by the Logitech Media Server to refer to
the player by name.
.TP
.B \-p <priority>
Set real time priority of output thread (1-99; default
.IR 45 ).
.TP
.B \-r <rate>
Maximum sample rate for the output device; this is required if the ALSA output
device is switched off when squeezelite is started.
.TP
.B \-u [params]
Enable upsampling of played audio. The argument is optional; see
.B RESAMPLING
(below) for more information.
.TP
.B \-v
Enable visualiser support. This creates a shared memory segment that contains
some of the audio being played, so that an external visualiser can read and
process this to create visualisations.
.TP
.B \-z
Cause \fBsqueezelite\fR to run as a daemon. That is, it detaches itself from the
terminal and runs in the background.
.TP
.B \-t
Display version and license information.
.SH RESAMPLING
Audio can be resampled or upsampled before being sent to the output device. This
can be enabled simply by passing the \fB\-u\fR option to \fBsqueezelite\fR, but
further configuration can be given as an argument to the option.
.PP
Resampling is performed using the SoX Resampler library; the documentation for
that library and the SoX \fIrate\fR effect many be helpful when configuring
upsampling for \fBsqueezelite\fR.
.PP
The format of the argument is
.B <recipe>:<flags>:<attenuation>:<precision>:<passband_end>:<stopband_start>:<phase_response>
.SS recipe
This part of the argument string is made up of a number of single-character
flags: \fB[v|h|m|l|q][L|I|M][s][X]\fR. The default value is \fBhL\fR.
.TP
.IR v ", " h ", " m ", " l " or " q
are mutually exclusive and correspond to very high, high, medium, low or quick
quality.
.TP
.IR L ", " I " or " M
correspond to linear, intermediate or minimum phase.
.TP
.IR s
changes resampling bandwidth from the default 95% (based on the 3dB point) to
99%.
.TP
.IR X
resamples to the maximum sample rate for the output device ("asynchronous"
resampling).
.TP
.B Examples
.B \-u vLs
would use very high quality setting, linear phase filter and steep cut-off.
.br
.B \-u hM
would specify high quality, with the minimum phase filter.
.br
.B \-u hMX
would specify high quality, with the minimum phase filter and async upsampling
to max device rate.
.SS flags
The second optional argument to \fB\-u\fR allows the user to specify the
following arguments (taken from the \fIsoxr.h\fR header file), in hex:
.sp
#define SOXR_ROLLOFF_SMALL     0u  /* <= 0.01 dB */
.br
#define SOXR_ROLLOFF_MEDIUM    1u  /* <= 0.35 dB */
.br
#define SOXR_ROLLOFF_NONE      2u  /* For Chebyshev bandwidth. */
.sp
#define SOXR_MAINTAIN_3DB_PT   4u  /* Reserved for internal use. */
.br
#define SOXR_HI_PREC_CLOCK     8u  /* Increase 'irrational' ratio accuracy. */
.br
#define SOXR_DOUBLE_PRECISION 16u  /* Use D.P. calcs even if precision <= 20. */
.br
#define SOXR_VR               32u  /* Experimental, variable-rate resampling. */
.TP
.B Examples
.B \-u :2
would specify \fBSOXR_ROLLOFF_NONE\fR.
.sp
\fBNB:\fR In the example above the first option, \fB<quality>\fR, has not been
specified so would default to \fBhL\fR. Therefore, specifying \fB\-u :2\fR is
equivalent to having specified \fB\-u hL:2\fR.
.SS attenuation
Internally, data is passed to the SoX resample process as 32 bit integers and
output from the SoX resample process as 32 bit integers. Why does this matter?
There is the possibility that integer samples, once resampled may be clipped
(i.e. exceed the maximum value). By default, if you do not specify an
\fBattenuation\fR value, it will default to \-1db. A value of \fI0\fR on the
command line, i.e. \fB-u ::0\fR will disable the default \-1db attenuation being
applied.
.sp
\fBNB:\fR Clipped samples will be logged. Keep an eye on the log file.
.TP
.B Examples
.B \-u ::6
specifies to apply \-6db (ie. halve the volume) prior to the resampling process.
.SS precision
The internal 'bit' precision used in the re-sampling calculations (ie. quality).
.sp
\fBNB:\fR HQ = 20, VHQ = 28.
.TP
.B Examples
.B \-u :::28
specifies 28-bit precision.
.SS passband_end
A percentage value between 0 and 100, where 100 is the Nyquist frequency. The
default if not explicitly set is \fI91.3\fR.
.TP
.B Examples
.B \-u ::::98
specifies passband ends at 98 percent of the Nyquist frequency.
.SS stopband_start
A percentage value between 0 and 100, where 100 is the Nyquist frequency. The
default if not explicitly set is \fI100\fR.
.TP
.B Examples
.B \-u :::::100
specifies that the stopband starts at the Nyquist frequency.
.SS phase_response
A value between 0-100, where \fI0\fR is equivalent to the recipe \fIM\fR flag
for minimum phase, \fI25\fR is equivalent to the recipe \fII\fR flag for
intermediate phase and \fI50\fR is equivalent to the recipe \fIL\fR flag for
linear phase.
.TP
.B Examples
.B \-u ::::::50
specifies linear phase.
.SH SEE ALSO
https://code.google.com/p/squeezelite/
.br
http://www.communitysqueeze.org/squeezelite_about.jsp
.br
http://www.communitysqueeze.org/squeezelite_upsample.jsp
.br
.BR sox (1)
\- for further information about resampling