--- /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 ***
projects / Faustine.git / blobdiff