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writeloop --help

writeloop (version 0.9.dev of frankl's stereo utilities)
USAGE:
  writeloop --block-size=<bsize> --file-size=<fsize> <file1> <file2> [<file3>..]

  This program 'writeloop' reads data from stdin or a file and writes them 
  cyclically into the files whose names <file1>, ..., are given on the 
  command line. (If the next file to be written exists then the program 
  will wait until it is deleted.)

  Some overhead can be saved by using shared memory files instead of files
  in a file system. See the --shared option below.

  USAGE HINTS
  
  This can be used together with 'catloop' which does the converse
  (reading the files cyclically and writing a stream to stdout).

  The given files should be on a ramdisk. writeloop/catloop provide
  a buffer for data read from a hard disk or from the network.
  
  OPTIONS

  --block-size=intval, -b intval
      the size in bytes of the data chunks written to the given filenames.
      Default is 2000 bytes.

  --file-size=intval, -f intval
      the maximal size of the written files (default is 64000).
  
  --from-file=fname,  -F fname
      read data from file fname instead of stdin.

  --shared, -s
      use named shared memory instead of files. The convention is that
      the given names start with a slash like '/file1'.
      For large amounts of shared memory you may need to enlarge
      '/proc/sys/kernel/shmmax' directly or via sysctl.

  --nfinfo=nfnam, -M nfnam
      with this and the following option input can be read from an nf file,
      this option specifies the nf info file.

  --nfid=id, -N id
      this is the nf id of the file to read, the id must be found in the 
      nf info file specified by the previous option.

  --force-shm, -x
      if --shared is used writeloop may fail to start if 'semaphores' are
      left over from former calls or other programs. With this option these
      are overwritten.

  --skip=intval, -S intval
      if input is a file then skip intval bytes at the beginning, the 
      argument is rounded down to a multiple of 8.

  --verbose, -v
      print some information during startup.

  --version, -V
      print information about the version of the program and abort.

  --help, -h
      print this help page and abort.

  EXAMPLE
  
  If you want to play an audio file (CD format) on a hard disk or on a 
  network file system, you can use writeloop and catloop as a buffer:

       sox /my/disk/cd.flac -t raw | writeloop --block-size=4000 \
                --file-size=20000 /ramdisk/aa /ramdisk/bb /ramdisk/cc &

  and 
       catloop --block-size=1000 /ramdisk/aa /ramdisk/bb /ramdisk/cc | \
             aplay -t raw -f S16_LE -c 2 -r44100 -D "hw:0,0" 

  Or similarly, using less system resources, with shared memory:

       sox /my/disk/cd.flac -t raw | writeloop --block-size=4000 \
                --file-size=20000 --shared /aa /bb /cc &

  and 
       catloop --block-size=1000 --shared /aa /bb /cc | \
             aplay -t raw -f S16_LE -c 2 -r44100 -D "hw:0,0" 

     
  In experiments I found that audio playback was improved compared to a 
  direct playing. For larger file sizes (a few megabytes) the effect was
  similar to copying the file into RAM and playing that file.
  But even better was the effect with small file sizes (a few kilobytes)
  such that all files fit into the processor cache.