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Friday, 1 January 2010

audioconvert man page

User Commands                                     audioconvert(1)

     audioconvert - convert audio file formats

     audioconvert [-pF]  [-f outfmt]  [-o outfile]  [  [-i infmt]
     [file...]] ...

     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.

     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.

SunOS 5.10          Last change: 16 Feb 2001                    1

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.

SunOS 5.10          Last change: 16 Feb 2001                    2

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

                     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.

SunOS 5.10          Last change: 16 Feb 2001                    3

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

SunOS 5.10          Last change: 16 Feb 2001                    4

User Commands                                     audioconvert(1)

                     cd       Equivalent                       to

                     dat      Equivalent                       to

     format          This option specifies the audio file format.
                     Valid formats are:

                     sun      Sun  compatible  file  format  (the

                     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.

     See largefile(5) for the  description  of  the  behavior  of
     audioconvert  when  encountering files greater than or equal
     to 2 Gbyte ( 2**31 bytes).

     Example 1: Recording and compressing voice data before stor-
     ing it

     Record voice data and compress it before  storing  it  to  a

     example% audiorecord | audioconvert -f g721 > mydata.au

SunOS 5.10          Last change: 16 Feb 2001                    5

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

     See attributes(5) for descriptions of the  following  attri-

    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    | Architecture                | SPARC, x86                  |
    | Availability                | SUNWauda                    |
    | Interface Stability         | Evolving                    |

     audioplay(1), audiorecord(1), file(1), attributes(5), large-

     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.

SunOS 5.10          Last change: 16 Feb 2001                    6

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