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/*
* Micronas SC-4 audio decoder
* Copyright (c) 2022 Paul B Mahol
*
* This file is part of FFmpeg.
*
* FFmpeg 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 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavutil/internal.h"
#include "libavutil/intreadwrite.h"
#include "avcodec.h"
#include "codec_internal.h"
#include "decode.h"
#include "bytestream.h"
#include "mathops.h"
static const int16_t steps[16] = {
4084, 18, 41, 64, 112, 198, 355, 1122,
1122, 355, 198, 112, 64, 41, 18, 4084,
};
static const int16_t diffs[16] = {
2048, 4, 135, 213, 273, 323, 373, 425,
425, 373, 323, 273, 213, 135, 4, 2048,
};
typedef struct ChannelContext {
unsigned last_step;
int64_t new_pred;
int64_t pred;
int64_t weights_tab[6];
int32_t diffs_tab[6];
} ChannelContext;
typedef struct MISC4Context {
GetByteContext gb;
uint32_t marker;
ChannelContext ch[2];
} MISC4Context;
static av_cold int misc4_init(AVCodecContext *avctx)
{
MISC4Context *s = avctx->priv_data;
avctx->sample_fmt = AV_SAMPLE_FMT_S16;
switch (avctx->sample_rate) {
case 8000:
case 11025:
s->marker = 0x11b;
break;
case 16000:
case 32000:
s->marker = 0x2b2;
break;
}
return 0;
}
#define FRACBITS 12
#define WEIGHTSBITS 26
static int64_t prediction(int delta, ChannelContext *c)
{
const int isign = FFDIFFSIGN(delta, 0);
int64_t dotpr = 0;
c->new_pred = delta * (1LL << FRACBITS) + c->pred;
for (int i = 0; i < 6; i++) {
const int sign = FFSIGN(c->diffs_tab[i]);
c->weights_tab[i] = (c->weights_tab[i] * 255LL) / 256;
c->weights_tab[i] += (1LL << (WEIGHTSBITS + 1)) * sign * isign;
}
memmove(&c->diffs_tab[1], &c->diffs_tab[0], 5 * sizeof(int32_t));
c->diffs_tab[0] = -delta * (1 << (FRACBITS-8));
c->pred = c->new_pred;
dotpr = 0;
for (int i = 0; i < 6; i++)
dotpr += ((int64_t)c->diffs_tab[i] * c->weights_tab[i]) >> WEIGHTSBITS;
c->pred += dotpr;
c->pred = av_clip64(c->pred, -16383 * (1 << FRACBITS), 16383 * (1 << FRACBITS));
c->pred = c->pred * 9 / 10;
return c->new_pred;
}
static int16_t decode(ChannelContext *c, unsigned nibble)
{
int diff, diff_sign, adiff = 0, delta;
uint32_t step, newstep;
int64_t pred;
diff_sign = nibble >> 3;
diff = diffs[nibble];
step = diff + (c->last_step >> 2);
newstep = step & 0xfff;
if (newstep >> 11 == 0)
adiff = (((step & 0x7f) + 0x80) * 128) >>
(14 - (newstep >> 7));
delta = diff_sign ? -adiff : adiff;
delta = av_clip_intp2(delta, 15);
pred = prediction(delta, c);
nibble = steps[nibble];
newstep = nibble * 32 - c->last_step & 0x1ffff;
newstep = ((newstep >> 5) + (newstep & 0x10000 ? 0x1000 : 0) + c->last_step) & 0x1fff;
c->last_step = av_clip(newstep, 544, 5120);
return av_clip_int16(pred >> (FRACBITS - 3));
}
static int misc4_decode(AVCodecContext *avctx, AVFrame *frame,
int *got_frame_ptr, AVPacket *pkt)
{
MISC4Context *s = avctx->priv_data;
GetByteContext *gb = &s->gb;
uint32_t hdr;
int ret;
bytestream2_init(gb, pkt->data, pkt->size);
frame->nb_samples = 29 * (1 + (avctx->ch_layout.nb_channels == 1));
if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
return ret;
hdr = bytestream2_peek_be32(gb);
if (hdr == s->marker) {
bytestream2_skip(gb, 5);
} else if ((hdr >> 16) == s->marker) {
bytestream2_skip(gb, 3);
}
{
int16_t *samples = (int16_t *)frame->data[0];
const int st = avctx->ch_layout.nb_channels == 2;
int n;
for (n = 0; n < 29; n++) {
int nibble = bytestream2_get_byte(gb);
samples[2*n+0] = decode(&s->ch[0 ], nibble >> 4);
samples[2*n+1] = decode(&s->ch[st], nibble & 15);
if (bytestream2_get_bytes_left(gb) <= 0)
break;
}
if (n == 29 && bytestream2_get_byte(gb) != 0x55)
return AVERROR_INVALIDDATA;
}
*got_frame_ptr = 1;
return bytestream2_tell(gb);
}
const FFCodec ff_misc4_decoder = {
.p.name = "misc4",
CODEC_LONG_NAME("Micronas SC-4 Audio"),
.p.type = AVMEDIA_TYPE_AUDIO,
.p.id = AV_CODEC_ID_MISC4,
.priv_data_size = sizeof(MISC4Context),
.init = misc4_init,
FF_CODEC_DECODE_CB(misc4_decode),
.p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_SUBFRAMES |
AV_CODEC_CAP_CHANNEL_CONF,
.p.sample_fmts = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_S16,
AV_SAMPLE_FMT_NONE },
};
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