ref: 7f5cc661487e713c96226a937b7c1818c51620bf
dir: /src/adpcms.c/
/*
* 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,
* Fifth Floor, 51 Franklin Street, Boston, MA 02111-1301, USA.
*/
/* ADPCM CODECs: IMA, OKI. (c) 2007 robs@users.sourceforge.net */
#include "st_i.h"
#include "adpcms.h"
static int const ima_steps[89] = { /* ~16-bit precision */
7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
50, 55, 60, 66, 73, 80, 88, 97, 107, 118, 130, 143, 157, 173, 190, 209, 230,
253, 279, 307, 337, 371, 408, 449, 494, 544, 598, 658, 724, 796, 876, 963,
1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024, 3327,
3660, 4026, 4428, 4871, 5358, 5894, 6484, 7132, 7845, 8630, 9493, 10442,
11487, 12635, 13899, 15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794,
32767 };
static int const oki_steps[49] = { /* ~12-bit precision */
256, 272, 304, 336, 368, 400, 448, 496, 544, 592, 656, 720, 800, 880, 960,
1056, 1168, 1280, 1408, 1552, 1712, 1888, 2080, 2288, 2512, 2768, 3040, 3344,
3680, 4048, 4464, 4912, 5392, 5936, 6528, 7184, 7904, 8704, 9568, 10528,
11584, 12736, 14016, 15408, 16960, 18656, 20512, 22576, 24832 };
static int const step_changes[8] = {-1, -1, -1, -1, 2, 4, 6, 8};
static void adpcm_init(adpcm_t state, int type)
{
state->last_output = 0;
state->step_index = 0;
state->max_step_index = type? 48 : 88;
state->steps = type? oki_steps : ima_steps;
state->mask = type? ~15 : ~0;
}
static int adpcm_decode(int code, adpcm_t state)
{
int s = ((code & 7) << 1) | 1;
s = ((state->steps[state->step_index] * s) >> 3) & state->mask;
if (code & 8)
s = -s;
s += state->last_output;
s = range_limit(s, -0x8000, 0x7fff);
state->step_index += step_changes[code & 0x07];
state->step_index = range_limit(state->step_index, 0, state->max_step_index);
return state->last_output = s;
}
static int adpcm_encode(int sample, adpcm_t state)
{
int delta = sample - state->last_output;
int sign = 0;
int code;
if (delta < 0) {
sign = 0x08;
delta = -delta;
}
code = 4 * delta / state->steps[state->step_index];
code = sign | min(code, 7);
adpcm_decode(code, state); /* Update encoder state */
return code;
}
/*
* Format methods
*
* Almost like the raw format functions, but cannot be used directly
* since they require an additional state parameter.
*/
/******************************************************************************
* Function : st_adpcm_reset
* Description: Resets the ADPCM codec state.
* Parameters : state - ADPCM state structure
* type - ST_ENCODING_OKI_ADPCM or ST_ENCODING_IMA_ADPCM
* Returns :
* Exceptions :
* Notes : 1. This function is used for framed ADPCM formats to reset
* the decoder between frames.
******************************************************************************/
void st_adpcm_reset(adpcm_io_t state, st_encoding_t type)
{
state->file.count = 0;
state->file.pos = 0;
state->file.eof = 0;
state->store.byte = 0;
state->store.flag = 0;
adpcm_init(&state->encoder, (type == ST_ENCODING_OKI_ADPCM) ? 1 : 0);
}
/******************************************************************************
* Function : adpcm_start
* Description: Initialises the file parameters and ADPCM codec state.
* Parameters : ft - file info structure
* state - ADPCM state structure
* type - ST_ENCODING_OKI_ADPCM or ST_ENCODING_IMA_ADPCM
* Returns : int - ST_SUCCESS
* ST_EOF
* Exceptions :
* Notes : 1. This function can be used as a startread or
* startwrite method.
* 2. VOX file format is 4-bit OKI ADPCM that decodes to
* to 12 bit signed linear PCM.
* 3. Dialogic only supports 6kHz, 8kHz and 11 kHz sampling
* rates but the codecs allows any user specified rate.
******************************************************************************/
static int adpcm_start(ft_t ft, adpcm_io_t state, st_encoding_t type)
{
/* setup file info */
state->file.buf = (char *) xmalloc(ST_BUFSIZ);
state->file.size = ST_BUFSIZ;
ft->signal.channels = 1;
st_adpcm_reset(state, type);
return st_rawstart(ft, st_true, st_false, type, ST_SIZE_16BIT, ST_OPTION_DEFAULT);
}
int st_adpcm_oki_start(ft_t ft, adpcm_io_t state)
{
return adpcm_start(ft, state, ST_ENCODING_OKI_ADPCM);
}
int st_adpcm_ima_start(ft_t ft, adpcm_io_t state)
{
return adpcm_start(ft, state, ST_ENCODING_IMA_ADPCM);
}
/******************************************************************************
* Function : st_adpcm_read
* Description: Fills an internal buffer from the VOX file, converts the
* OKI ADPCM 4-bit samples to 12-bit signed PCM and then scales
* the samples to full range 16 bit PCM.
* Parameters : ft - file info structure
* state - ADPCM state structure
* buffer - output buffer
* length - size of output buffer
* Returns : int - number of samples returned in buffer
* Exceptions :
* Notes :
******************************************************************************/
st_size_t st_adpcm_read(ft_t ft, adpcm_io_t state, st_sample_t * buffer, st_size_t len)
{
st_size_t n;
uint8_t byte;
for (n = 0; n < (len&~1) && st_readb(ft, &byte) == ST_SUCCESS; n += 2) {
short word = adpcm_decode(byte >> 4, &state->encoder);
*buffer++ = ST_SIGNED_WORD_TO_SAMPLE(word, ft->clips);
word = adpcm_decode(byte, &state->encoder);
*buffer++ = ST_SIGNED_WORD_TO_SAMPLE(word, ft->clips);
}
return n;
}
/******************************************************************************
* Function : stopread
* Description: Frees the internal buffer allocated in voxstart/imastart.
* Parameters : ft - file info structure
* state - ADPCM state structure
* Returns : int - ST_SUCCESS
* Exceptions :
* Notes :
******************************************************************************/
int st_adpcm_stopread(ft_t ft UNUSED, adpcm_io_t state)
{
free(state->file.buf);
return (ST_SUCCESS);
}
/******************************************************************************
* Function : write
* Description: Converts the supplied buffer to 12 bit linear PCM and encodes
* to OKI ADPCM 4-bit samples (packed a two nibbles per byte).
* Parameters : ft - file info structure
* state - ADPCM state structure
* buffer - output buffer
* length - size of output buffer
* Returns : int - ST_SUCCESS
* ST_EOF
* Exceptions :
* Notes :
******************************************************************************/
st_size_t st_adpcm_write(ft_t ft, adpcm_io_t state, const st_sample_t * buffer, st_size_t length)
{
st_size_t count = 0;
uint8_t byte = state->store.byte;
uint8_t flag = state->store.flag;
short word;
while (count < length) {
word = ST_SAMPLE_TO_SIGNED_WORD(*buffer++, ft->clips);
byte <<= 4;
byte |= adpcm_encode(word, &state->encoder) & 0x0F;
flag = !flag;
if (flag == 0) {
state->file.buf[state->file.count++] = byte;
if (state->file.count >= state->file.size) {
st_writebuf(ft, state->file.buf, 1, state->file.count);
state->file.count = 0;
}
}
count++;
}
/* keep last byte across calls */
state->store.byte = byte;
state->store.flag = flag;
return (count);
}
/******************************************************************************
* Function : st_adpcm_flush
* Description: Flushes any leftover samples.
* Parameters : ft - file info structure
* state - ADPCM state structure
* Returns :
* Exceptions :
* Notes : 1. Called directly for writing framed formats
******************************************************************************/
void st_adpcm_flush(ft_t ft, adpcm_io_t state)
{
uint8_t byte = state->store.byte;
uint8_t flag = state->store.flag;
/* flush remaining samples */
if (flag != 0) {
byte <<= 4;
byte |= adpcm_encode(0, &state->encoder) & 0x0F;
state->file.buf[state->file.count++] = byte;
}
if (state->file.count > 0)
st_writebuf(ft, state->file.buf, 1, state->file.count);
}
/******************************************************************************
* Function : st_adpcm_stopwrite
* Description: Flushes any leftover samples and frees the internal buffer
* allocated in voxstart/imastart.
* Parameters : ft - file info structure
* state - ADPCM state structure
* Returns : int - ST_SUCCESS
* Exceptions :
* Notes :
******************************************************************************/
int st_adpcm_stopwrite(ft_t ft, adpcm_io_t state)
{
st_adpcm_flush(ft, state);
free(state->file.buf);
return (ST_SUCCESS);
}