Manipulation binary files

[Chris]

Dear All,

I'm trying to use perl in a way I am not usd to, and coming unstuck :-(

I have a binary file of unsigned byte values, and I wish to convert these
into a .wav file, so that I can use the soundcard DAC to generate the
waveform the binary file describes (cool huh? Cheap signal generator

The problem is that the wav file format needs to have all all sorts of stuff
munged into the header, including strings "RIFF" "WAVE" and "fmt " and
values that describe other paramters. SOme of these data types are 32 bit,
some are 16 some are 8.

In perl how do i ...

a) write to a file in binary mode. I have tried using binmode(FH) before the
writing beging, but it seems to make little difference

b) write strings in binary mode. I dont really have to do write 0x52 0x49
0x46 0x46 if there is a way to write "RIFF" and have perl do the donkey work

c) Declare the widths of my variables. I need to be able to assign a
variable with a value, and output all 4 bytes of that value to the file in
binary mode.

I'm guessing that all this is very easy, and I'm just looking in the wrong
place :-(

Cheers

Chris

 

[Eric J. Roode]

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Hash: SHA1

I have a binary file of unsigned byte values, and I wish to convert
these into a .wav file, so that I can use the soundcard DAC to
generate the waveform the binary file describes (cool huh? Cheap
signal generator

The problem is that the wav file format needs to have all all sorts of
stuff munged into the header, including strings "RIFF" "WAVE" and "fmt
" and values that describe other paramters. SOme of these data types
are 32 bit, some are 16 some are 8.

In perl how do i ...

a) write to a file in binary mode. I have tried using binmode(FH)
before the writing beging, but it seems to make little difference

To write to a binary file, you use "print", just like writing to a text
file. You should use binmode on the file handle beforehand, yes.

b) write strings in binary mode. I dont really have to do write 0x52
0x49 0x46 0x46 if there is a way to write "RIFF" and have perl do the
donkey work

Yes: print FH "RIFF";

c) Declare the widths of my variables. I need to be able to assign a
variable with a value, and output all 4 bytes of that value to the
file in binary mode.

You should look into the 'pack' operator. It's a pain to use (imho), but
this is exactly what it does: convert numeric variables into binary
strings, suitable for printing to your file.

- --
Eric
$_ = reverse sort $ /. r , qw p ekca lre uJ reh
ts p , map $ _. $ " , qw e p h tona e and print

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[John W. Krahn]

To write to a binary file, you use "print", just like writing to a text
file. You should use binmode on the file handle beforehand, yes.


Yes: print FH "RIFF";

And you may want to turn on autoflush for your output file handle. Have
a look in perlvar.pod for "OUTPUT_AUTOFLUSH".


John

 

[Anno Siegel]

And you may want to turn on autoflush for your output file handle. Have
a look in perlvar.pod for "OUTPUT_AUTOFLUSH".

How would that make a difference? If the file is a normal disk file,
I don't see the use of autoflush.

Anno