User Commands audioconvert(1)
NAME
audioconvert - convert audio file formats
SYNOPSIS
audioconvert [-pF] [-f outfmt] [-o outfile] [ [-i infmt]
[file...]] ...
DESCRIPTION
audioconvert converts audio data between a set of supported
audio encodings and file formats. It can be used to compress
and decompress audio data, to add audio file headers to raw
audio data files, and to convert between standard data
encodings, such as -law and linear PCM.
If no filenames are present, audioconvert reads the data
from the standard input stream and writes an audio file to
the standard output. Otherwise, input files are processed in
order, concatenated, and written to the output file.
Input files are expected to contain audio file headers that
identify the audio data format. If the audio data does not
contain a recognizable header, the format must be specified
with the -i option, using the rate, encoding, and channels
keywords to identify the input data format.
The output file format is derived by updating the format of
the first input file with the format options in the -f
specification. If -p is not specified, all subsequent input
files are converted to this resulting format and con-
catenated together. The output file will contain an audio
file header, unless format=raw is specified in the output
format options.
Input files may be converted in place by using the -p
option. When -p is in effect, the format of each input file
is modified according to the -f option to determine the out-
put format. The existing files are then overwritten with the
converted data.
The file(1) command decodes and prints the audio data format
of Sun audio files.
OPTIONS
The following options are supported:
-p In Place: The input files are individually
converted to the format specified by the -f
option and rewritten. If a target file is a
symbolic link, the underlying file will be
rewritten. The -o option may not be speci-
fied with -p.
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User Commands audioconvert(1)
-F Force: This option forces audioconvert to
ignore any file header for input files whose
format is specified by the -i option. If -F
is not specified, audioconvert ignores the
-i option for input files that contain valid
audio file headers.
-f outfmt Output Format: This option is used to
specify the file format and data encoding of
the output file. Defaults for unspecified
fields are derived from the input file for-
mat. Valid keywords and values are listed in
the next section.
-o outfile Output File: All input files are con-
catenated, converted to the output format,
and written to the named output file. If -o
and -p are not specified, the concatenated
output is written to the standard output.
The -p option may not be specified with -o.
-i infmt Input Format: This option is used to specify
the data encoding of raw input files. Ordi-
narily, the input data format is derived
from the audio file header. This option is
required when converting audio data that is
not preceded by a valid audio file header.
If -i is specified for an input file that
contains an audio file header, the input
format string will be ignored, unless -F is
present. The format specification syntax is
the same as the -f output file format.
Multiple input formats may be specified. An
input format describes all input files fol-
lowing that specification, until a new input
format is specified.
file File Specification: The named audio files
are concatenated, converted to the output
format, and written out. If no file name is
present, or if the special file name `-' is
specified, audio data is read from the stan-
dard input.
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User Commands audioconvert(1)
-? Help: Prints a command line usage message.
Format Specification
The syntax for the input and output format specification is:
keyword=value[,keyword=value ...]
with no intervening whitespace. Unambiguous values may be
used without the preceding keyword=.
rate The audio sampling rate is specified in sam-
ples per second. If a number is followed by
the letter k, it is multiplied by 1000 (for
example, 44.1k = 44100). Standard of the
commonly used sample rates are: 8k, 16k,
32k, 44.1k, and 48k.
channels The number of interleaved channels is speci-
fied as an integer. The words mono and
stereo may also be used to specify one and
two channel data, respectively.
encoding This option specifies the digital audio data
representation. Encodings determine preci-
sion implicitly (ulaw implies 8-bit preci-
sion) or explicitly as part of the name (for
example, linear16). Valid encoding values
are:
ulaw CCITT G.711 -law encoding.
This is an 8-bit format pri-
marily used for telephone
quality speech.
alaw CCITT G.711 A-law encoding.
This is an 8-bit format pri-
marily used for telephone
quality speech in Europe.
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User Commands audioconvert(1)
linear8, Linear Pulse Code Modulation
linear16, (PCM) encoding. The name
linear32 identifies the number of
bits of precision. linear16
is typically used for high
quality audio data.
pcm Same as linear16.
g721 CCITT G.721 compression for-
mat. This encoding uses
Adaptive Delta Pulse Code
Modulation (ADPCM) with 4-
bit precision. It is pri-
marily used for compressing
-law voice data (achieving a
2:1 compression ratio).
g723 CCITT G.723 compression for-
mat. This encoding uses
Adaptive Delta Pulse Code
Modulation (ADPCM) with 3-
bit precision. It is pri-
marily used for compressing
-law voice data (achieving
an 8:3 compression ratio).
The audio quality is similar
to G.721, but may result in
lower quality when used for
non-speech data.
The following encoding values are also
accepted as shorthand to set the sample
rate, channels, and encoding:
voice Equivalent to
encoding=ulaw,rate=8k,channels=mono.
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User Commands audioconvert(1)
cd Equivalent to
encoding=linear16,rate=44.1k,channels=stereo.
dat Equivalent to
encoding=linear16,rate=48k,channels=stereo.
format This option specifies the audio file format.
Valid formats are:
sun Sun compatible file format (the
default).
raw Use this format when reading or
writing raw audio data (with no
audio header), or in conjunction
with an offset to import a foreign
audio file format.
offset (-i only) Specifies a byte offset to locate
the start of the audio data. This option may
be used to import audio data that contains
an unrecognized file header.
USAGE
See largefile(5) for the description of the behavior of
audioconvert when encountering files greater than or equal
to 2 Gbyte ( 2**31 bytes).
EXAMPLES
Example 1: Recording and compressing voice data before stor-
ing it
Record voice data and compress it before storing it to a
file:
example% audiorecord | audioconvert -f g721 > mydata.au
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User Commands audioconvert(1)
Example 2: Concatenating two audio files
Concatenate two Sun format audio files, regardless of their
data format, and output an 8-bit ulaw, 16 kHz, mono file:
example% audioconvert -f ulaw,rate=16k,mono -o outfile.au infile1 infile2
Example 3: Converting a directory to Sun format
Convert a directory containing raw voice data files, in
place, to Sun format (adds a file header to each file):
example% audioconvert -p -i voice -f sun *.au
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Architecture | SPARC, x86 |
|_____________________________|_____________________________|
| Availability | SUNWauda |
|_____________________________|_____________________________|
| Interface Stability | Evolving |
|_____________________________|_____________________________|
SEE ALSO
audioplay(1), audiorecord(1), file(1), attributes(5), large-
file(5)
NOTES
The algorithm used for converting multi-channel data to mono
is implemented by simply summing the channels together. If
the input data is perfectly in phase (as would be the case
if a mono file is converted to stereo and back to mono), the
resulting data may contain some distortion.
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Friday 1 January 2010
audioconvert man page
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