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