SoX(7) Sound eXchange SoX(7)NAME
SoX - Sound eXchange, the Swiss Army knife of audio manipulation
DESCRIPTION
This manual describes SoX supported file formats and audio device
types; the SoX manual set starts with sox(1).
Format types that can SoX can determine by a filename extension are
listed with their names preceded by a dot. Format types that are
optionally built into SoX are marked `(optional)'.
Format types that can be handled by an external library via an optional
pseudo file type (currently sndfile or ffmpeg) are marked e.g. `(also
with -t sndfile)'. This might be useful if you have a file that
doesn't work with SoX's default format readers and writers, and there's
an external reader or writer for that format.
To see if SoX has support for an optional format or device, enter sox
-h and look for its name under the list: `AUDIO FILE FORMATS' or `AUDIO
DEVICE DRIVERS'.
SOX FORMATS & DEVICE DRIVERS
.raw (also with -t sndfile), .f32, .f64, .s8, .s16, .s24, .s32,
.u8, .u16, .u24, .u32, .ul, .al, .lu, .la
Raw (headerless) audio files. For raw, the sample rate and the
data encoding must be given using command-line format options;
for the other listed types, the sample rate defaults to 8kHz
(but may be overridden), and the data encoding is defined by the
given suffix. Thus f32 and f64 indicate files encoded as 32 and
64-bit (IEEE single and double precision) floating point PCM
respectively; s8, s16, s24, and s32 indicate 8, 16, 24, and
32-bit signed integer PCM respectively; u8, u16, u24, and u32
indicate 8, 16, 24, and 32-bit unsigned integer PCM respec‐
tively; ul indicates `μ-law' (8-bit), al indicates `A-law'
(8-bit), and lu and la are inverse bit order `μ-law' and inverse
bit order `A-law' respectively. For all raw formats, the number
of channels defaults to 1 (but may be overridden).
Headerless audio files on a SPARC computer are likely to be of
format ul; on a Mac, they're likely to be u8 but with a sample
rate of 11025 or 22050 Hz.
See .ima and .vox for raw ADPCM formats, and .cdda for raw CD
digital audio.
.f4, .f8, .s1, .s2, .s3, .s4,
.u1, .u2, .u3, .u4, .sb, .sw, .sl, .ub, .uw
Deprecated aliases for f32, f64, s8, s16, s24, s32,
u8, u16, u24, u32, s8, s16, s32, u8, and u16 respectively.
.8svx (also with -t sndfile)
Amiga 8SVX musical instrument description format.
.aiff, .aif (also with -t sndfile)
AIFF files as used on old Apple Macs, Apple IIc/IIgs and SGI.
SoX's AIFF support does not include multiple audio chunks, or
the 8SVX musical instrument description format. AIFF files are
multimedia archives and can have multiple audio and picture
chunks - you may need a separate archiver to work with them.
With Mac OS X, AIFF has been superseded by CAF.
.aiffc, .aifc (also with -t sndfile)
AIFF-C is a format based on AIFF that was created to allow han‐
dling compressed audio. It can also handle little endian uncom‐
pressed linear data that is often referred to as sowt encoding.
This encoding has also become the defacto format produced by
modern Macs as well as iTunes on any platform. AIFF-C files
produced by other applications typically have the file extension
.aif and require looking at its header to detect the true for‐
mat. The sowt encoding is the only encoding that SoX can handle
with this format.
AIFF-C is defined in DAVIC 1.4 Part 9 Annex B. This format is
referred from ARIB STD-B24, which is specified for Japanese data
broadcasting. Any private chunks are not supported.
alsa (optional)
Advanced Linux Sound Architecture device driver; supports both
playing and recording audio. ALSA is only used in Linux-based
operating systems, though these often support OSS (see below) as
well. Examples:
sox infile -t alsa
sox infile -t alsa default
sox infile -t alsa plughw:0,0
sox -2 -t alsa hw:1 outfile
See also play(1), rec(1), and sox(1)-d.
.amb Ambisonic B-Format: a specialisation of .wav with between 3 and
16 channels of audio for use with an Ambisonic decoder. See
http://www.ambisonia.com/Members/mleese/file-format-for-b-format
for details. It is up to the user to get the channels together
in the right order and at the correct amplitude.
.amr-nb (optional)
Adaptive Multi Rate - Narrow Band speech codec; a lossy format
used in 3rd generation mobile telephony and defined in 3GPP TS
26.071 et al.
AMR-NB audio has a fixed sampling rate of 8 kHz and supports
encoding to the following bit-rates (as selected by the -C
option): 0 = 4.75 kbit/s, 1 = 5.15 kbit/s, 2 = 5.9 kbit/s, 3 =
6.7 kbit/s, 4 = 7.4 kbit/s 5 = 7.95 kbit/s, 6 = 10.2 kbit/s, 7 =
12.2 kbit/s.
.amr-wb (optional)
Adaptive Multi Rate - Wide Band speech codec; a lossy format
used in 3rd generation mobile telephony and defined in 3GPP TS
26.171 et al.
AMR-WB audio has a fixed sampling rate of 16 kHz and supports
encoding to the following bit-rates (as selected by the -C
option): 0 = 6.6 kbit/s, 1 = 8.85 kbit/s, 2 = 12.65 kbit/s, 3 =
14.25 kbit/s, 4 = 15.85 kbit/s 5 = 18.25 kbit/s, 6 = 19.85
kbit/s, 7 = 23.05 kbit/s, 8 = 23.85 kbit/s.
ao (optional)
Xiph.org's Audio Output device driver; works only for playing
audio. It supports a wide range of devices and sound systems -
see its documentation for the full range. For the most part,
SoX's use of libao cannot be configured directly; instead, libao
configuration files must be used.
The filename specified is used to determine which libao plugin
to use. Normally, you should specify `default' as the filename.
If that doesn't give the desired behavior then you can specify
the short name for a given plugin (such as pulse for pulse audio
plugin). Examples:
sox infile -t ao
sox infile -t ao default
sox infile -t ao pulse
See also play(1) and sox(1)-d.
.au, .snd (also with -t sndfile)
Sun Microsystems AU files. There are many types of AU file; DEC
has invented its own with a different magic number and byte
order. To write a DEC file, use the -L option with the output
file options.
Some .au files are known to have invalid AU headers; these are
probably original Sun μ-law 8000 Hz files and can be dealt with
using the .ul format (see below).
It is possible to override AU file header information with the
-r and -c options, in which case SoX will issue a warning to
that effect.
.avr Audio Visual Research format; used by a number of commercial
packages on the Mac.
.caf (optional)
Apple's Core Audio File format.
.cdda, .cdr
`Red Book' Compact Disc Digital Audio (raw audio). CDDA has two
audio channels formatted as 16-bit signed integers (big
endian)at a sample rate of 44.1 kHz. The number of (stereo)
samples in each CDDA track is always a multiple of 588.
coreaudio (optional)
Mac OSX CoreAudio device driver: supports both playing and
recording audio. If a filename is not specific or if the name
is "default" then the default audio device is selected. Any
other name will be used to select a specific device. The valid
names can be seen in the System Preferences->Sound menu and then
under the Output and Input tabs.
Examples:
sox infile -t coreaudio
sox infile -t coreaudio default
sox infile -t coreaudio "Internal Speakers"
See also play(1), rec(1), and sox(1)-d.
.cvsd, .cvs
Continuously Variable Slope Delta modulation. A headerless for‐
mat used to compress speech audio for applications such as voice
mail. This format is sometimes used with bit-reversed samples -
the -X format option can be used to set the bit-order.
.cvu Continuously Variable Slope Delta modulation (unfiltered). This
is an alternative handler for CVSD that is unfiltered but can be
used with any bit-rate. E.g.
sox infile outfile.cvu rate 28k
play -r 28k outfile.cvu sinc -3.4k
.dat Text Data files. These files contain a textual representation
of the sample data. There is one line at the beginning that
contains the sample rate. Subsequent lines contain two numeric
data items: the time since the beginning of the first sample and
the sample value. Values are normalized so that the maximum and
minimum are 1 and -1. This file format can be used to create
data files for external programs such as FFT analysers or graph
routines. SoX can also convert a file in this format back into
one of the other file formats.
.dvms, .vms
Used in Germany to compress speech audio for voice mail. A
self-describing variant of cvsd.
.fap (optional)
See .paf.
ffmpeg (optional)
This is a pseudo-type that forces ffmpeg to be used. The actual
file type is deduced from the file name (it cannot be used on
stdio). It can read a wide range of audio files, not all of
which are documented here, and also the audio track of many
video files (including AVI, WMV and MPEG). At present only the
first audio track of a file can be read.
.flac (optional; also with -t sndfile)
Xiph.org's Free Lossless Audio CODEC compressed audio. FLAC is
an open, patent-free CODEC designed for compressing music. It
is similar to MP3 and Ogg Vorbis, but lossless, meaning that
audio is compressed in FLAC without any loss in quality.
SoX can read native FLAC files (.flac) but not Ogg FLAC files
(.ogg). [But see .ogg below for information relating to support
for Ogg Vorbis files.]
SoX can write native FLAC files according to a given or default
compression level. 8 is the default compression level and gives
the best (but slowest) compression; 0 gives the least (but
fastest) compression. The compression level is selected using
the -C option [see sox(1)] with a whole number from 0 to 8.
.fssd An alias for the .u8 format.
.gsrt Grandstream ring-tone files. Whilst this file format can con‐
tain A-Law, μ-law, GSM, G.722, G.723, G.726, G.728, or iLBC
encoded audio, SoX supports reading and writing only A-Law and
μ-law. E.g.
sox music.wav -t gsrt ring.bin
play ring.bin
.gsm (optional; also with -t sndfile)
GSM 06.10 Lossy Speech Compression. A lossy format for com‐
pressing speech which is used in the Global Standard for Mobile
telecommunications (GSM). It's good for its purpose, shrinking
audio data size, but it will introduce lots of noise when a
given audio signal is encoded and decoded multiple times. This
format is used by some voice mail applications. It is rather
CPU intensive.
.hcom Macintosh HCOM files. These are Mac FSSD files with Huffman
compression.
.htk Single channel 16-bit PCM format used by HTK, a toolkit for
building Hidden Markov Model speech processing tools.
.ircam (also with -t sndfile)
Another name for .sf.
.ima (also with -t sndfile)
A headerless file of IMA ADPCM audio data. IMA ADPCM claims
16-bit precision packed into only 4 bits, but in fact sounds no
better than .vox.
.lpc, .lpc10
LPC-10 is a compression scheme for speech developed in the
United States. See http://www.arl.wustl.edu/~jaf/lpc/ for
details. There is no associated file format, so SoX's implemen‐
tation is headerless.
.mat, .mat4, .mat5 (optional)
Matlab 4.2/5.0 (respectively GNU Octave 2.0/2.1) format (.mat is
the same as .mat4).
.m3u A playlist format; contains a list of audio files. SoX can
read, but not write this file format. See [1] for details of
this format.
.maud An IFF-conforming audio file type, registered by MS MacroSystem
Computer GmbH, published along with the `Toccata' sound-card on
the Amiga. Allows 8bit linear, 16bit linear, A-Law, μ-law in
mono and stereo.
.mp3, .mp2 (optional read, optional write)
MP3 compressed audio; MP3 (MPEG Layer 3) is a part of the
patent-encumbered MPEG standards for audio and video compres‐
sion. It is a lossy compression format that achieves good com‐
pression rates with little quality loss.
Because MP3 is patented, SoX cannot be distributed with MP3 sup‐
port without incurring the patent holder's fees. Users who
require SoX with MP3 support must currently compile and build
SoX with the MP3 libraries (LAME & MAD) from source code, or, in
some cases, obtain pre-built dynamically loadable libraries.
When reading MP3 files, up to 28 bits of precision is stored
although only 16 bits is reported to user. This is to allow
default behavior of writing 16 bit output files. A user can
specify a higher precision for the output file to prevent loss‐
ing this extra information. MP3 output files will use up to 24
bits of precision while encoding.
MP3 compression parameters can be selected using SoX's -C option
as follows (note that the current syntax is subject to change):
The primary parameter to the LAME encoder is the bit rate. If
the value of the -C value is a positive integer, it's taken as
the bitrate in kbps (e.g. if you specify 128, it uses 128 kbps).
The second most important parameter is probably "quality"
(really performance), which allows balancing encoding speed vs.
quality. In LAME, 0 specifies highest quality but is very slow,
while 9 selects poor quality, but is fast. (5 is the default and
2 is recommended as a good trade-off for high quality encodes.)
Because the -C value is a float, the fractional part is used to
select quality. 128.2 selects 128 kbps encoding with a quality
of 2. There is one problem with this approach. We need 128 to
specify 128 kbps encoding with default quality, so 0 means use
default. Instead of 0 you have to use .01 (or .99) to specify
the highest quality (128.01 or 128.99).
LAME uses bitrate to specify a constant bitrate, but higher
quality can be achieved using Variable Bit Rate (VBR). VBR qual‐
ity (really size) is selected using a number from 0 to 9. Use a
value of 0 for high quality, larger files, and 9 for smaller
files of lower quality. 4 is the default.
In order to squeeze the selection of VBR into the the -C value
float we use negative numbers to select VRR. -4.2 would select
default VBR encoding (size) with high quality (speed). One spe‐
cial case is 0, which is a valid VBR encoding parameter but not
a valid bitrate. Compression value of 0 is always treated as a
high quality vbr, as a result both -0.2 and 0.2 are treated as
highest quality VBR (size) and high quality (speed).
See also Ogg Vorbis for a similar format.
.mp4, .m4a (optional)
MP4 compressed audio. MP3 (MPEG 4) is part of the MPEG stan‐
dards for audio and video compression. See mp3 for more infor‐
mation.
.nist (also with -t sndfile)
See .sph.
.ogg, .vorbis (optional)
Xiph.org's Ogg Vorbis compressed audio; an open, patent-free
CODEC designed for music and streaming audio. It is a lossy
compression format (similar to MP3, VQF & AAC) that achieves
good compression rates with a minimum amount of quality loss.
SoX can decode all types of Ogg Vorbis files, and can encode at
different compression levels/qualities given as a number from -1
(highest compression/lowest quality) to 10 (lowest compression,
highest quality). By default the encoding quality level is 3
(which gives an encoded rate of approx. 112kbps), but this can
be changed using the -C option (see above) with a number from -1
to 10; fractional numbers (e.g. 3.6) are also allowed. Decod‐
ing is somewhat CPU intensive and encoding is very CPU inten‐
sive.
See also .mp3 for a similar format.
oss (optional)
Open Sound System /dev/dsp device driver; supports both playing
and recording audio. OSS support is available in Unix-like
operating systems, sometimes together with alternative sound
systems (such as ALSA). Examples:
sox infile -t oss
sox infile -t oss /dev/dsp
sox -2 -t oss /dev/dsp outfile
See also play(1), rec(1), and sox(1)-d.
.paf, .fap (optional)
Ensoniq PARIS file format (big and little-endian respectively).
.pls A playlist format; contains a list of audio files. SoX can
read, but not write this file format. See [2] for details of
this format.
Note: SoX support for SHOUTcast PLS relies on wget(1) and is
only partially supported: it's necessary to specify the audio
type manually, e.g.
play -t mp3 "http://a.server/pls?rn=265&file=filename.pls"
and SoX does not know about alternative servers - hit Ctrl-C
twice in quick succession to quit.
.prc Psion Record. Used in Psion EPOC PDAs (Series 5, Revo and simi‐
lar) for System alarms and recordings made by the built-in
Record application. When writing, SoX defaults to A-law, which
is recommended; if you must use ADPCM, then use the -i switch.
The sound quality is poor because Psion Record seems to insist
on frames of 800 samples or fewer, so that the ADPCM CODEC has
to be reset at every 800 frames, which causes the sound to
glitch every tenth of a second.
pulseaudio (optional)
PulseAudio driver; supports both playing and recording of audio.
PulseAudio is a cross platform networked sound server. If a
file name is specified with this driver, it is ignored. Exam‐
ples:
sox infile -t pulseaudio
sox infile -t pulseaudio default
See also play(1), rec(1), and sox(1)-d.
.pvf (optional)
Portable Voice Format.
.sd2 (optional)
Sound Designer 2 format.
.sds (optional)
MIDI Sample Dump Standard.
.sf (also with -t sndfile)
IRCAM SDIF (Institut de Recherche et Coordination Acous‐
tique/Musique Sound Description Interchange Format). Used by
academic music software such as the CSound package, and the
MixView sound sample editor.
.sph, .nist (also with -t sndfile)
SPHERE (SPeech HEader Resources) is a file format defined by
NIST (National Institute of Standards and Technology) and is
used with speech audio. SoX can read these files when they con‐
tain μ-law and PCM data. It will ignore any header information
that says the data is compressed using shorten compression and
will treat the data as either μ-law or PCM. This will allow SoX
and the command line shorten program to be run together using
pipes to encompasses the data and then pass the result to SoX
for processing.
.smp Turtle Beach SampleVision files. SMP files are for use with the
PC-DOS package SampleVision by Turtle Beach Softworks. This
package is for communication to several MIDI samplers. All sam‐
ple rates are supported by the package, although not all are
supported by the samplers themselves. Currently loop points are
ignored.
.snd See .au, .sndr and .sndt.
sndfile (optional)
This is a pseudo-type that forces libsndfile to be used. For
writing files, the actual file type is then taken from the out‐
put file name; for reading them, it is deduced from the file.
sndio (optional)
OpenBSD audio device driver; supports both playing and recording
audio.
sox infile -t sndio
See also play(1), rec(1), and sox(1)-d.
.sndr Sounder files. An MS-DOS/Windows format from the early '90s.
Sounder files usually have the extension `.SND'.
.sndt SoundTool files. An MS-DOS/Windows format from the early '90s.
SoundTool files usually have the extension `.SND'.
.sou An alias for the .u8 raw format.
.sox SoX's native uncompressed PCM format, intended for storing (or
piping) audio at intermediate processing points (i.e. between
SoX invocations). It has much in common with the popular WAV,
AIFF, and AU uncompressed PCM formats, but has the following
specific characteristics: the PCM samples are always stored as
32 bit signed integers, the samples are stored (by default) as
`native endian', and the number of samples in the file is
recorded as a 64-bit integer. Comments are also supported.
See `Special Filenames' in sox(1) for examples of using the .sox
format with `pipes'.
sunau (optional)
Sun /dev/audio device driver; supports both playing and record‐
ing audio. For example:
sox infile -t sunau /dev/audio
or
sox infile -t sunau -U -c 1 /dev/audio
for older sun equipment.
See also play(1), rec(1), and sox(1)-d.
.txw Yamaha TX-16W sampler. A file format from a Yamaha sampling
keyboard which wrote IBM-PC format 3.5" floppies. Handles read‐
ing of files which do not have the sample rate field set to one
of the expected by looking at some other bytes in the
attack/loop length fields, and defaulting to 33 kHz if the sam‐
ple rate is still unknown.
.vms See .dvms.
.voc (also with -t sndfile)
Sound Blaster VOC files. VOC files are multi-part and contain
silence parts, looping, and different sample rates for different
chunks. On input, the silence parts are filled out, loops are
rejected, and sample data with a new sample rate is rejected.
Silence with a different sample rate is generated appropriately.
On output, silence is not detected, nor are impossible sample
rates. SoX supports reading (but not writing) VOC files with
multiple blocks, and files containing μ-law, A-law, and
2/3/4-bit ADPCM samples.
.vorbis
See .ogg.
.vox (also with -t sndfile)
A headerless file of Dialogic/OKI ADPCM audio data commonly
comes with the extension .vox. This ADPCM data has 12-bit pre‐
cision packed into only 4-bits.
Note: some early Dialogic hardware does not always reset the
ADPCM encoder at the start of each vox file. This can result in
clipping and/or DC offset problems when it comes to decoding the
audio. Whilst little can be done about the clipping, a DC off‐
set can be removed by passing the decoded audio through a high-
pass filter, e.g.:
sox input.vox output.wav highpass 10
.w64 (optional)
Sonic Foundry's 64-bit RIFF/WAV format.
.wav (also with -t sndfile)
Microsoft .WAV RIFF files. This is the native audio file format
of Windows, and widely used for uncompressed audio.
Normally .wav files have all formatting information in their
headers, and so do not need any format options specified for an
input file. If any are, they will override the file header, and
you will be warned to this effect. You had better know what you
are doing! Output format options will cause a format conversion,
and the .wav will written appropriately.
SoX can read and write linear PCM, μ-law, A-law, MS ADPCM, and
IMA (or DVI) ADPCM. WAV files can also contain audio encoded in
many other ways (not currently supported with SoX) e.g. MP3; in
some cases such a file can still be read by SoX by overriding
the file type, e.g.
play -t mp3 mp3-encoded.wav
Big endian versions of RIFF files, called RIFX, are also sup‐
ported. To write a RIFX file, use the -B option with the output
file options.
waveaudio (optional)
MS-Windows native audio device driver. Examples:
sox infile -t waveaudio
sox infile -t waveaudio default
sox infile -t waveaudio 1
sox infile -t waveaudio "High Definition Audio Device ("
If the device name is omitted, -1, or default, then you get the
`Microsoft Wave Mapper' device. Wave Mapper means `use the sys‐
tem default audio devices'. You can control what `default'
means via the OS Control Panel.
If the device name given is some other number, you get that
audio device by index; so recording with device name 0 would get
the first input device (perhaps the microphone), 1 would get the
second (perhaps line in), etc. Playback using 0 will get the
first output device (usually the only audio device).
If the device name given is something other than a number, SoX
tries to match it (maximum 31 characters) against the names of
the available devices.
See also play(1), rec(1), and sox(1)-d.
.wavpcm
A non-standard, but widely used, variant of .wav. Some applica‐
tions cannot read a standard WAV file header for PCM-encoded
data with sample-size greater than 16-bits or with more than two
channels, but can read a non-standard WAV header. It is likely
that such applications will eventually be updated to support the
standard header, but in the mean time, this SoX format can be
used to create files with the non-standard header that should
work with these applications. (Note that SoX will automatically
detect and read WAV files with the non-standard header.)
The most common use of this file-type is likely to be along the
following lines:
sox infile.any -t wavpcm -s outfile.wav
.wv (optional)
WavPack lossless audio compression. Note that, when converting
.wav to this format and back again, the RIFF header is not nec‐
essarily preserved losslessly (though the audio is).
.wve (also with -t sndfile)
Psion 8-bit A-law. Used on Psion SIBO PDAs (Series 3 and simi‐
lar). This format is deprecated in SoX, but will continue to be
used in libsndfile.
.xa Maxis XA files. These are 16-bit ADPCM audio files used by
Maxis games. Writing .xa files is currently not supported,
although adding write support should not be very difficult.
.xi (optional)
Fasttracker 2 Extended Instrument format.
SEE ALSOsox(1), soxi(1), libsox(3), octave(1), wget(1)
The SoX web page at http://sox.sourceforge.net
SoX scripting examples at http://sox.sourceforge.net/Docs/Scripts
References
[1] Wikipedia, M3U, http://en.wikipedia.org/wiki/M3U
[2] Wikipedia, PLS, http://en.wikipedia.org/wiki/PLS_(file_format)LICENSE
Copyright 1998-2011 Chris Bagwell and SoX Contributors.
Copyright 1991 Lance Norskog and Sundry Contributors.
AUTHORS
Chris Bagwell (cbagwell@users.sourceforge.net). Other authors and con‐
tributors are listed in the ChangeLog file that is distributed with the
source code.
soxformat February 19, 2011 SoX(7)
