audioconvert(1) User Commands audioconvert(1)NAMEaudioconvert - convert audio file formats
SYNOPSISaudioconvert [-pF] [-f outfmt] [-o outfile]
[ [-i infmt] [file]...] ...
DESCRIPTIONaudioconvert 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 stan‐
dard input stream and writes an audio file to the standard output. Oth‐
erwise, 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 recogniz‐
able header, the format must be specified with the -i option, using the
rate, encoding, and channels keywords to identify the input data for‐
mat.
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 result‐
ing format and concatenated 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 output 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 specified with -p.
-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 concatenated, 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. Ordinarily, the input data
format is derived from the audio file header. This option
is required when converting audio data that is not pre‐
ceded 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 following that specification,
until a new input format is specified.
file File Specification: The named audio files are concate‐
nated, 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 standard
input.
-? 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 samples per second.
If a number is followed by the letter k, it is multiplied
by 1000 (for example, 44.1k = 44100). Standard of the com‐
monly used sample rates are: 8k, 16k, 32k, 44.1k, and 48k.
channels The number of interleaved channels is specified as an inte‐
ger. 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 representa‐
tion. Encodings determine precision implicitly (ulaw
implies 8-bit precision) 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 primarily used for telephone quality
speech.
alaw CCITT G.711 A-law encoding. This is an 8-bit
format primarily used for telephone quality
speech in Europe.
linear8, Linear Pulse Code Modulation (PCM) encoding.
linear16, The name identifies the number of bits of pre‐
linear32 cision. linear16 is typically used for high
quality audio data.
pcm Same as linear16.
g721 CCITT G.721 compression format. This encoding
uses Adaptive Delta Pulse Code Modulation
(ADPCM) with 4-bit precision. It is primarily
used for compressing -law voice data (achiev‐
ing a 2:1 compression ratio).
g723 CCITT G.723 compression format. This encoding
uses Adaptive Delta Pulse Code Modulation
(ADPCM) with 3-bit precision. It is primarily
used for compressing -law voice data (achiev‐
ing an 8:3 compression ratio). The audio qual‐
ity 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 short‐
hand to set the sample rate, channels, and encoding:
voice Equivalent to encoding=ulaw,rate=8k,channels=mono.
cd Equivalent to encoding=linear16,rate=44.1k,chan‐
nels=stereo.
dat Equivalent to encoding=linear16,rate=48k,chan‐
nels=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 storing it
Record voice data and compress it before storing it to a file:
example% audiorecord | audioconvert-f g721 > mydata.au
Example 2 Concatenating two audio files
Concatenate two Sun format audio files, regardless of their data for‐
mat, 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 attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Architecture │SPARC, x86 │
├─────────────────────────────┼─────────────────────────────┤
│Availability │audio/audio-utilities │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Committed │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOaudioplay(1), audiorecord(1), file(1), attributes(5), largefile(5)NOTES
The algorithm used for converting multi-channel data to mono is imple‐
mented 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 distor‐
tion.
SunOS 5.11 16 Feb 2001 audioconvert(1)
