ref: 210336f9b78b4089163bc16804a1e76984c6c46d
dir: /src/ima_rw.h/
/*
ima_rw.h -- codex utilities for WAV_FORMAT_IMA_ADPCM
Copyright (C) 1999 Stanley J. Brooks <stabro@megsinet.net>
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "st.h"
#ifndef SAMPL
# define SAMPL short
#endif
/* #undef STRICT_IMA makes code a bit faster, but not
* strictly compatible with the real IMA spec, which
* defines an encoding on approximate multiply/divide
* using shift/adds instead of the (now) faster mult/div
* Probably the roundof inexactness is inaudibly small,
* so you might consider it worthwhile to #undef STRICT_IMA
*/
#define STRICT_IMA
/* #undef STRICT_IMA */
/*
* call initImaTable() before any other Ima* functions,
* to create the fast lookup tables
*/
extern void initImaTable(void);
/* ImaBlockExpandI() outputs interleaved samples into one output buffer */
extern void ImaBlockExpandI(
int chans, /* total channels */
const unsigned char *ibuff,/* input buffer[blockAlign] */
SAMPL *obuff, /* output samples, n*chans */
int n /* samples to decode PER channel, REQUIRE n % 8 == 1 */
);
/* ImaBlockExpandM() outputs non-interleaved samples into chan separate output buffers */
extern void ImaBlockExpandM(
int chans, /* total channels */
const unsigned char *ibuff,/* input buffer[blockAlign] */
SAMPL **obuffs, /* chan output sample buffers, each takes n samples */
int n /* samples to decode PER channel, REQUIRE n % 8 == 1 */
);
/* mash one block. if you want to use opt>0, 9 is a reasonable value */
extern void ImaBlockMashI(
int chans, /* total channels */
const SAMPL *ip, /* ip[] is interleaved input samples */
int n, /* samples to encode PER channel, REQUIRE n % 8 == 1 */
int *st, /* input/output state[chans], REQUIRE 0 <= st[ch] <= ISSTMAX */
unsigned char *obuff, /* output buffer[blockAlign] */
int opt /* non-zero allows some cpu-intensive code to improve output */
);
/* Some helper functions for computing samples/block and blockalign */
/*
* ImaSamplesIn(dataLen, chans, blockAlign, samplesPerBlock)
* returns the number of samples/channel which would go
* in the dataLen, given the other parameters ...
* if input samplesPerBlock is 0, then returns the max
* samplesPerBlock which would go into a block of size blockAlign
* Yes, it is confusing usage.
*/
extern st_size_t ImaSamplesIn(
st_size_t dataLen,
unsigned short chans,
unsigned short blockAlign,
unsigned short samplesPerBlock
);
/*
* st_size_t ImaBytesPerBlock(chans, samplesPerBlock)
* return minimum blocksize which would be required
* to encode number of chans with given samplesPerBlock
*/
extern st_size_t ImaBytesPerBlock(
unsigned short chans,
unsigned short samplesPerBlock
);