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FFmpeg/libavcodec/dpcm.c
Mike Melanson c89c1d2542 handle 0-length buffers 
Originally committed as revision 2731 to svn://svn.ffmpeg.org/ffmpeg/trunk
2004-01-31 17:30:28 +00:00

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8.2 KiB
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/*
* Assorted DPCM codecs
* Copyright (c) 2003 The ffmpeg Project.
*
* 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
*/
/**
* @file: dpcm.c
* Assorted DPCM (differential pulse code modulation) audio codecs
* by Mike Melanson (melanson@pcisys.net)
* Xan DPCM decoder by Mario Brito (mbrito@student.dei.uc.pt)
* for more information on the specific data formats, visit:
* http://www.pcisys.net/~melanson/codecs/simpleaudio.html
*
* Note about using the Xan DPCM decoder: Xan DPCM is used in AVI files
* found in the Wing Commander IV computer game. These AVI files contain
* WAVEFORMAT headers which report the audio format as 0x01: raw PCM.
* Clearly incorrect. To detect Xan DPCM, you will probably have to
* special-case your AVI demuxer to use Xan DPCM if the file uses 'Xxan'
* (Xan video) for its video codec. Alternately, such AVI files also contain
* the fourcc 'Axan' in the 'auds' chunk of the AVI header.
*/
#include "avcodec.h"
typedef struct DPCMContext {
int channels;
short roq_square_array[256];
} DPCMContext;
#define SATURATE_S16(x) if (x < -32768) x = -32768; \
else if (x > 32767) x = 32767;
#define SE_16BIT(x) if (x & 0x8000) x -= 0x10000;
#define LE_16(x) ((((uint8_t*)(x))[1] << 8) | ((uint8_t*)(x))[0])
#define LE_32(x) ((((uint8_t*)(x))[3] << 24) | \
(((uint8_t*)(x))[2] << 16) | \
(((uint8_t*)(x))[1] << 8) | \
((uint8_t*)(x))[0])
static int interplay_delta_table[] = {
0, 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 22, 23,
24, 25, 26, 27, 28, 29, 30, 31,
32, 33, 34, 35, 36, 37, 38, 39,
40, 41, 42, 43, 47, 51, 56, 61,
66, 72, 79, 86, 94, 102, 112, 122,
133, 145, 158, 173, 189, 206, 225, 245,
267, 292, 318, 348, 379, 414, 452, 493,
538, 587, 640, 699, 763, 832, 908, 991,
1081, 1180, 1288, 1405, 1534, 1673, 1826, 1993,
2175, 2373, 2590, 2826, 3084, 3365, 3672, 4008,
4373, 4772, 5208, 5683, 6202, 6767, 7385, 8059,
8794, 9597, 10472, 11428, 12471, 13609, 14851, 16206,
17685, 19298, 21060, 22981, 25078, 27367, 29864, 32589,
-29973, -26728, -23186, -19322, -15105, -10503, -5481, -1,
1, 1, 5481, 10503, 15105, 19322, 23186, 26728,
29973, -32589, -29864, -27367, -25078, -22981, -21060, -19298,
-17685, -16206, -14851, -13609, -12471, -11428, -10472, -9597,
-8794, -8059, -7385, -6767, -6202, -5683, -5208, -4772,
-4373, -4008, -3672, -3365, -3084, -2826, -2590, -2373,
-2175, -1993, -1826, -1673, -1534, -1405, -1288, -1180,
-1081, -991, -908, -832, -763, -699, -640, -587,
-538, -493, -452, -414, -379, -348, -318, -292,
-267, -245, -225, -206, -189, -173, -158, -145,
-133, -122, -112, -102, -94, -86, -79, -72,
-66, -61, -56, -51, -47, -43, -42, -41,
-40, -39, -38, -37, -36, -35, -34, -33,
-32, -31, -30, -29, -28, -27, -26, -25,
-24, -23, -22, -21, -20, -19, -18, -17,
-16, -15, -14, -13, -12, -11, -10, -9,
-8, -7, -6, -5, -4, -3, -2, -1
};
static int dpcm_decode_init(AVCodecContext *avctx)
{
DPCMContext *s = avctx->priv_data;
int i;
short square;
s->channels = avctx->channels;
switch(avctx->codec->id) {
case CODEC_ID_ROQ_DPCM:
/* initialize square table */
for (i = 0; i < 128; i++) {
square = i * i;
s->roq_square_array[i] = square;
s->roq_square_array[i + 128] = -square;
}
break;
default:
break;
}
return 0;
}
static int dpcm_decode_frame(AVCodecContext *avctx,
void *data, int *data_size,
uint8_t *buf, int buf_size)
{
DPCMContext *s = avctx->priv_data;
int in, out = 0;
int predictor[2];
int channel_number = 0;
short *output_samples = data;
int shift[2];
unsigned char byte;
short diff;
if (!buf_size)
return 0;
switch(avctx->codec->id) {
case CODEC_ID_ROQ_DPCM:
if (s->channels == 1)
predictor[0] = LE_16(&buf[6]);
else {
predictor[0] = buf[7] << 8;
predictor[1] = buf[6] << 8;
}
SE_16BIT(predictor[0]);
SE_16BIT(predictor[1]);
/* decode the samples */
for (in = 8, out = 0; in < buf_size; in++, out++) {
predictor[channel_number] += s->roq_square_array[buf[in]];
SATURATE_S16(predictor[channel_number]);
output_samples[out] = predictor[channel_number];
/* toggle channel */
channel_number ^= s->channels - 1;
}
break;
case CODEC_ID_INTERPLAY_DPCM:
in = 6; /* skip over the stream mask and stream length */
predictor[0] = LE_16(&buf[in]);
in += 2;
SE_16BIT(predictor[0])
output_samples[out++] = predictor[0];
if (s->channels == 2) {
predictor[1] = LE_16(&buf[in]);
in += 2;
SE_16BIT(predictor[1])
output_samples[out++] = predictor[1];
}
while (in < buf_size) {
predictor[channel_number] += interplay_delta_table[buf[in++]];
SATURATE_S16(predictor[channel_number]);
output_samples[out++] = predictor[channel_number];
/* toggle channel */
channel_number ^= s->channels - 1;
}
break;
case CODEC_ID_XAN_DPCM:
in = 0;
shift[0] = shift[1] = 4;
predictor[0] = LE_16(&buf[in]);
in += 2;
SE_16BIT(predictor[0]);
if (s->channels == 2) {
predictor[1] = LE_16(&buf[in]);
in += 2;
SE_16BIT(predictor[1]);
}
while (in < buf_size) {
byte = buf[in++];
diff = (byte & 0xFC) << 8;
if ((byte & 0x03) == 3)
shift[channel_number]++;
else
shift[channel_number] -= (2 * (byte & 3));
/* saturate the shifter to a lower limit of 0 */
if (shift[channel_number] < 0)
shift[channel_number] = 0;
diff >>= shift[channel_number];
predictor[channel_number] += diff;
SATURATE_S16(predictor[channel_number]);
output_samples[out++] = predictor[channel_number];
/* toggle channel */
channel_number ^= s->channels - 1;
}
break;
}
*data_size = out * sizeof(short);
return buf_size;
}
AVCodec roq_dpcm_decoder = {
"roq_dpcm",
CODEC_TYPE_AUDIO,
CODEC_ID_ROQ_DPCM,
sizeof(DPCMContext),
dpcm_decode_init,
NULL,
NULL,
dpcm_decode_frame,
};
AVCodec interplay_dpcm_decoder = {
"interplay_dpcm",
CODEC_TYPE_AUDIO,
CODEC_ID_INTERPLAY_DPCM,
sizeof(DPCMContext),
dpcm_decode_init,
NULL,
NULL,
dpcm_decode_frame,
};
AVCodec xan_dpcm_decoder = {
"xan_dpcm",
CODEC_TYPE_AUDIO,
CODEC_ID_XAN_DPCM,
sizeof(DPCMContext),
dpcm_decode_init,
NULL,
NULL,
dpcm_decode_frame,
};
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