+++ /dev/null
-new_file_type.HOWTO
-===================
-
- Original : Wed May 23 19:05:07 EST 2001
- Update 1 : Fri Jul 11 22:12:38 EST 2003
-
-This document will attempt to explain as fully as possible how to add code to
-libsndfile to allow the reading and writing of new file types. By new file
-type I particularly mean a new header type rather than a new encoding method
-for an existing file type.
-
-This HOWTO will take the form of a step by step guide. It will assume that you
-have all required tools including :
-
- - gcc
- - make (should really be the GNU version)
- - autoconf
- - automake
- - libtool
-
-These should all be available on the GNU ftp site: ftp://ftp.gnu.org/pub/gnu/.
-
-To help make these steps clearer let's suppose we are adding support for the
-Whacky file format whose files contain 'W','A','C' and 'K' as the first four
-bytes of the file format. Lets also assume that Whacky files contain PCM encoded
-data.
-
-Step 1
-------
-Create a new .c file in the src/ directory of the libsndfile source tree. The
-file name should be reasonable descriptive so that is is obvious that files of
-the new type are handled by this file. In this particular case the file might
-be named 'whacky.c'.
-
-Step 2
-------
-Add your new source code file to the build process.
-
-Edit the file src/Makefile.am and add the name of your file handler to the
-FILESPECIFIC list of handlers. This list looks something like this:
-
-FILESPECIFIC = aiff.c au.c au_g72x.c nist.c paf.c raw.c samplitude.c \
- svx.c wav.c wav_float.c wav_gsm610.c wav_ima_adpcm.c \
- wav_ms_adpcm.c
-
-Then, run the script named 'reconf' in the libsndfile top level directory,
-which will run autoconf and other associated tools. Finally run "./configure"
-in the top level directory. You may want to use the "--disable-gcc-opt" option
-to disable gcc optimisations and make debugging with gdb/ddd easier.
-
-Step 3
-------
-Add a unique identifier for the new file type.
-
-Edit src/sndfile.h.in and find the enum containing the SF_FORMAT_XXX identifiers.
-Since you will be adding a major file type you should add your identifier to the
-top part of the list where the values are above 0x10000 in value. The easiest
-way to do this is to find the largest value in the list, add 0x10000 to it and
-make that your new identifier value. The identifier should be something like
-SF_FORMAT_WACK.
-
-Step 4
-------
-Add code to the file type recogniser function.
-
-Edit src/sndfile.c and find the function guess_file_type (). This function
-reads the first 3 ints of the file and from that makes a guess at the file
-type. In our case we would add:
-
-
- if (buffer [0] == MAKE_MARKER ('W','A','C','K'))
- return SF_FORMAT_WACK ;
-
-The use of the MAKE_MARKER macro should be pretty obvious and it is defined at the
-top of file should you need to have a look at it.
-
-Step 5
-------
-Add a call to your open function from psf_open_file ().
-
-Edit src/sndfile.c and find the switch statement in psf_open_file (). It starts
-like this:
-
- switch (filetype)
- { case SF_FORMAT_WAV :
- error = wav_open (psf) ;
- break ;
-
- case SF_FORMAT_AIFF :
- error = aiff_open (psf) ;
- break ;
-
-Towards the bottom of this switch statement your should add one for the new file
-type. Something like:
-
- case SF_FORMAT_WACK :
- sf_errno = whacky_open (psf) ;
- break ;
-
-Setp 6
-------
-Add prototypes for new open read and open write functions.
-
-Edit src/common.h, go to the bottom of the file and add something like
-
- int whacky_open (SF_PRIVATE *psf) ;
-
-Step 7
-------
-
-Implement your open read function. The best way to do this is by coding
-something much like one of the other file formats. The file src/au.c might be
-a good place to start.
-
-In src/whacky.c you should now implement the function whacky_open() which
-was prototyped in src/common.h. This function should return 0 on success and
-a non-zero number on error.
-
-Error values are defined in src/common.h in a enum which starts at SFE_NO_ERROR.
-When adding a new error value, you also need to add an error string to the
-SndfileErrors array in src/sndfile.c.
-
-To parse the header of your new file type you should avoid using standard read/
-write/seek functions (and the fread/fwrite/fseek etc) and instead use
-psf_binheader_readf () which is implemented and documented in src/common.h.
-
-During the parsing process, you should also print logging information to
-libsndfile's internal log buffer using the psf_log_printf() function.
-
-At the end of the open read process, you should have set a number of fields in the
-SF_PRIVATE structure pointed to by psf.
-
-
-
-*** THIS FILE IS INCOMPLETE ***
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