NAME¶
squeezelite - Lightweight headless Squeezebox emulator
SYNOPSIS¶
squeezelite [
options]
DESCRIPTION¶
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.
The player is controlled using, and media is streamed from, a Logitech Media
Server instance running somewhere on the local network.
OPTIONS¶
This program supports the following options:
- -h
- Show a summary of the available command-line options.
- -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).
- -o <output device>
- Specify the audio output device; the default value is default. Use
the -l option to list available output devices. - can be
used to output raw samples to standard output.
- -l
- List available audio output devices to stdout and exit. These device names
can be passed to the -o option in order to select a particular
device or configuration to use for audio playback.
- -a <params>
- Specify parameters used when opening an audio output device. For ALSA, the
format <b>:<p>:<f>:<m> is used where
<b> is the buffer time in milliseconds (values less than 500)
or size in bytes (default 40ms); <p> is the period
count (values less than 50) or size in bytes (default 4 periods);
<f> is the sample format (possible values: 16,
24, 24_3 or 32); <m> is whether to use
mmap (possible values: 0 or 1). For PortAudio, the value is
simply the target latency in milliseconds. When the output is sent to
standard output, the value can be 16, 24 or 32, which
denotes the sample size in bits.
- -b <stream>:<output>
- Specify internal stream and output buffer sizes in kilobytes.
- -c <codec1>,...
- Restrict codecs to those specified, otherwise load all available codecs.
Use squeezelite -h to obtain the list of codecs built into
squeezelite.
- -d <category>=<level>
- Set logging level. Categories are: all, slimproto,
stream, decode or output. Levels can be: info,
debug or sdebug. The option can be repeated to set different
log levels for different categories.
- -e <codec1>,...
- Explicitly exclude native support of one or more codecs. See also
-c, above.
- -f <logfile>
- Send logging output to a log file instead of standard output or standard
error.
- -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.
- -n <name>
- Set the player name. This name is used by the Logitech Media Server to
refer to the player by name. This option is mututally exclusive with
-N.
- -N <filename>
- Allow the server to set the player's name. The player name is stored in
the file pointed to by <filename> so that it can persist
between restarts. This option is mututally exclusive with -n.
- -p <priority>
- Set real time priority of output thread (1-99; default 45). Not
applicable when using PortAudio.
- -r <rates>[:<delay>]
- Specify sample rates supported by the output device; this is required if
the output device is switched off when squeezelite is started. The
format is either a single maximum sample rate, a range of sample rates in
the format <min>-<max>, or a comma-separated
list of available rates. Delay is an optional time to wait when switching
sample rates between tracks, in milliseconds.
- -u|-R [params]
- Enable upsampling of played audio. The argument is optional; see
RESAMPLING (below) for more information. The options -u and
-R are synonymous.
- -D [delay]
- Output device supports DSD over PCM (DoP). DSD streams will be converted
to DoP before output. If this option is not supplied, DSD streams will be
converted to PCM and resampled, so they can be played on a PCM DAC. Delay
is an optional time to wait when switching between PCM and DoP between
tracks, in milliseconds.
- -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.
- -z
- Cause squeezelite to run as a daemon. That is, it detaches itself
from the terminal and runs in the background.
- -t
- Display version and license information.
RESAMPLING¶
Audio can be resampled or upsampled before being sent to the output device. This
can be enabled simply by passing the
-u option to
squeezelite,
but further configuration can be given as an argument to the option.
Resampling is performed using the SoX Resampler library; the documentation for
that library and the SoX
rate effect many be helpful when configuring
upsampling for
squeezelite.
The format of the argument is
<recipe>:<flags>:<attenuation>:<precision>:<passband_end>:<stopband_start>:<phase_response>
recipe¶
This part of the argument string is made up of a number of single-character
flags:
[v|h|m|l|q][L|I|M][s][E|X]. The default value is
hL.
- v, h, m, l or q
- are mutually exclusive and correspond to very high, high, medium, low or
quick quality.
- L, I or M
- correspond to linear, intermediate or minimum phase.
- s
- changes resampling bandwidth from the default 95% (based on the 3dB point)
to 99%.
- E
- exception - avoids resampling if the output device supports the playback
sample rate natively.
- X
- resamples to the maximum sample rate for the output device
("asynchronous" resampling).
- Examples
- -u vLs would use very high quality setting, linear phase filter and
steep cut-off.
-u hM would specify high quality, with the minimum phase filter.
-u hMX would specify high quality, with the minimum phase filter and
async upsampling to max device rate.
flags¶
The second optional argument to
-u allows the user to specify the
following arguments (taken from the
soxr.h header file), in hex:
#define SOXR_ROLLOFF_SMALL 0u /* <= 0.01 dB */
#define SOXR_ROLLOFF_MEDIUM 1u /* <= 0.35 dB */
#define SOXR_ROLLOFF_NONE 2u /* For Chebyshev bandwidth. */
#define SOXR_MAINTAIN_3DB_PT 4u /* Reserved for internal use. */
#define SOXR_HI_PREC_CLOCK 8u /* Increase 'irrational' ratio accuracy. */
#define SOXR_DOUBLE_PRECISION 16u /* Use D.P. calcs even if precision <= 20.
*/
#define SOXR_VR 32u /* Experimental, variable-rate resampling. */
- Examples
- -u :2 would specify SOXR_ROLLOFF_NONE.
NB: In the example above the first option, <quality>,
has not been specified so would default to hL. Therefore,
specifying -u :2 is equivalent to having specified -u
hL:2.
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
attenuation value, it will default to -1db. A value of
0 on the
command line, i.e.
-u ::0 will disable the default -1db attenuation
being applied.
NB: Clipped samples will be logged. Keep an eye on the log file.
- Examples
- -u ::6 specifies to apply -6db (ie. halve the volume) prior to the
resampling process.
precision¶
The internal 'bit' precision used in the re-sampling calculations (ie. quality).
NB: HQ = 20, VHQ = 28.
- Examples
- -u :::28 specifies 28-bit precision.
passband_end¶
A percentage value between 0 and 100, where 100 is the Nyquist frequency. The
default if not explicitly set is
91.3.
- Examples
- -u ::::98 specifies passband ends at 98 percent of the Nyquist
frequency.
stopband_start¶
A percentage value between 0 and 100, where 100 is the Nyquist frequency. The
default if not explicitly set is
100.
- Examples
- -u :::::100 specifies that the stopband starts at the Nyquist
frequency.
phase_response¶
A value between 0-100, where
0 is equivalent to the recipe
M flag
for minimum phase,
25 is equivalent to the recipe
I flag for
intermediate phase and
50 is equivalent to the recipe
L flag for
linear phase.
- Examples
- -u ::::::50 specifies linear phase.
SEE ALSO¶
https://code.google.com/p/squeezelite/
http://www.communitysqueeze.org/squeezelite_about.jsp
http://www.communitysqueeze.org/squeezelite_upsample.jsp
sox(1) - for further information about resampling