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| 1 | +/* |
| 2 | + * Micronas SC-4 audio decoder |
| 3 | + * Copyright (c) 2022 Paul B Mahol |
| 4 | + * |
| 5 | + * This file is part of FFmpeg. |
| 6 | + * |
| 7 | + * FFmpeg is free software; you can redistribute it and/or |
| 8 | + * modify it under the terms of the GNU Lesser General Public |
| 9 | + * License as published by the Free Software Foundation; either |
| 10 | + * version 2.1 of the License, or (at your option) any later version. |
| 11 | + * |
| 12 | + * FFmpeg is distributed in the hope that it will be useful, |
| 13 | + * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 15 | + * Lesser General Public License for more details. |
| 16 | + * |
| 17 | + * You should have received a copy of the GNU Lesser General Public |
| 18 | + * License along with FFmpeg; if not, write to the Free Software |
| 19 | + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 20 | + */ |
| 21 | + |
| 22 | +#include "libavutil/internal.h" |
| 23 | +#include "libavutil/intreadwrite.h" |
| 24 | +#include "avcodec.h" |
| 25 | +#include "codec_internal.h" |
| 26 | +#include "decode.h" |
| 27 | +#include "bytestream.h" |
| 28 | +#include "mathops.h" |
| 29 | + |
| 30 | +static const int16_t steps[16] = { |
| 31 | + 4084, 18, 41, 64, 112, 198, 355, 1122, |
| 32 | + 1122, 355, 198, 112, 64, 41, 18, 4084, |
| 33 | +}; |
| 34 | + |
| 35 | +static const int16_t diffs[16] = { |
| 36 | + 2048, 4, 135, 213, 273, 323, 373, 425, |
| 37 | + 425, 373, 323, 273, 213, 135, 4, 2048, |
| 38 | +}; |
| 39 | + |
| 40 | +typedef struct ChannelContext { |
| 41 | + unsigned last_step; |
| 42 | + int64_t new_pred; |
| 43 | + int64_t pred; |
| 44 | + int64_t weights_tab[6]; |
| 45 | + int32_t diffs_tab[6]; |
| 46 | +} ChannelContext; |
| 47 | + |
| 48 | +typedef struct MISC4Context { |
| 49 | + GetByteContext gb; |
| 50 | + |
| 51 | + uint32_t marker; |
| 52 | + |
| 53 | + ChannelContext ch[2]; |
| 54 | +} MISC4Context; |
| 55 | + |
| 56 | +static av_cold int misc4_init(AVCodecContext *avctx) |
| 57 | +{ |
| 58 | + MISC4Context *s = avctx->priv_data; |
| 59 | + |
| 60 | + avctx->sample_fmt = AV_SAMPLE_FMT_S16; |
| 61 | + switch (avctx->sample_rate) { |
| 62 | + case 8000: |
| 63 | + case 11025: |
| 64 | + s->marker = 0x11b; |
| 65 | + break; |
| 66 | + case 16000: |
| 67 | + case 32000: |
| 68 | + s->marker = 0x2b2; |
| 69 | + break; |
| 70 | + } |
| 71 | + |
| 72 | + return 0; |
| 73 | +} |
| 74 | + |
| 75 | +#define FRACBITS 12 |
| 76 | +#define WEIGHTSBITS 26 |
| 77 | + |
| 78 | +static int64_t prediction(int delta, ChannelContext *c) |
| 79 | +{ |
| 80 | + const int isign = FFDIFFSIGN(delta, 0); |
| 81 | + int64_t dotpr = 0; |
| 82 | + |
| 83 | + c->new_pred = delta * (1LL << FRACBITS) + c->pred; |
| 84 | + |
| 85 | + for (int i = 0; i < 6; i++) { |
| 86 | + const int sign = FFSIGN(c->diffs_tab[i]); |
| 87 | + c->weights_tab[i] = (c->weights_tab[i] * 255LL) / 256; |
| 88 | + c->weights_tab[i] += (1LL << (WEIGHTSBITS + 1)) * sign * isign; |
| 89 | + } |
| 90 | + |
| 91 | + memmove(&c->diffs_tab[1], &c->diffs_tab[0], 5 * sizeof(int32_t)); |
| 92 | + |
| 93 | + c->diffs_tab[0] = -delta * (1 << (FRACBITS-8)); |
| 94 | + c->pred = c->new_pred; |
| 95 | + |
| 96 | + dotpr = 0; |
| 97 | + for (int i = 0; i < 6; i++) |
| 98 | + dotpr += ((int64_t)c->diffs_tab[i] * c->weights_tab[i]) >> WEIGHTSBITS; |
| 99 | + |
| 100 | + c->pred += dotpr; |
| 101 | + c->pred = av_clip64(c->pred, -16383 * (1 << FRACBITS), 16383 * (1 << FRACBITS)); |
| 102 | + c->pred = c->pred * 9 / 10; |
| 103 | + |
| 104 | + return c->new_pred; |
| 105 | +} |
| 106 | + |
| 107 | +static int16_t decode(ChannelContext *c, unsigned nibble) |
| 108 | +{ |
| 109 | + int diff, diff_sign, adiff = 0, delta; |
| 110 | + uint32_t step, newstep; |
| 111 | + int64_t pred; |
| 112 | + |
| 113 | + diff_sign = nibble >> 3; |
| 114 | + diff = diffs[nibble]; |
| 115 | + step = diff + (c->last_step >> 2); |
| 116 | + newstep = step & 0xfff; |
| 117 | + if (newstep >> 11 == 0) |
| 118 | + adiff = (((step & 0x7f) + 0x80) * 128) >> |
| 119 | + (14 - (newstep >> 7)); |
| 120 | + delta = diff_sign ? -adiff : adiff; |
| 121 | + delta = av_clip_intp2(delta, 15); |
| 122 | + pred = prediction(delta, c); |
| 123 | + nibble = steps[nibble]; |
| 124 | + newstep = nibble * 32 - c->last_step & 0x1ffff; |
| 125 | + newstep = ((newstep >> 5) + (newstep & 0x10000 ? 0x1000 : 0) + c->last_step) & 0x1fff; |
| 126 | + c->last_step = av_clip(newstep, 544, 5120); |
| 127 | + |
| 128 | + return av_clip_int16(pred >> (FRACBITS - 3)); |
| 129 | +} |
| 130 | + |
| 131 | +static int misc4_decode(AVCodecContext *avctx, AVFrame *frame, |
| 132 | + int *got_frame_ptr, AVPacket *pkt) |
| 133 | +{ |
| 134 | + MISC4Context *s = avctx->priv_data; |
| 135 | + GetByteContext *gb = &s->gb; |
| 136 | + uint32_t hdr; |
| 137 | + int ret; |
| 138 | + |
| 139 | + bytestream2_init(gb, pkt->data, pkt->size); |
| 140 | + |
| 141 | + frame->nb_samples = 29 * (1 + (avctx->ch_layout.nb_channels == 1)); |
| 142 | + if ((ret = ff_get_buffer(avctx, frame, 0)) < 0) |
| 143 | + return ret; |
| 144 | + |
| 145 | + hdr = bytestream2_peek_be32(gb); |
| 146 | + if (hdr == s->marker) { |
| 147 | + bytestream2_skip(gb, 5); |
| 148 | + } else if ((hdr >> 16) == s->marker) { |
| 149 | + bytestream2_skip(gb, 3); |
| 150 | + } |
| 151 | + |
| 152 | + { |
| 153 | + int16_t *samples = (int16_t *)frame->data[0]; |
| 154 | + const int st = avctx->ch_layout.nb_channels == 2; |
| 155 | + int n; |
| 156 | + |
| 157 | + for (n = 0; n < 29; n++) { |
| 158 | + int nibble = bytestream2_get_byte(gb); |
| 159 | + samples[2*n+0] = decode(&s->ch[0 ], nibble >> 4); |
| 160 | + samples[2*n+1] = decode(&s->ch[st], nibble & 15); |
| 161 | + if (bytestream2_get_bytes_left(gb) <= 0) |
| 162 | + break; |
| 163 | + } |
| 164 | + |
| 165 | + if (n == 29 && bytestream2_get_byte(gb) != 0x55) |
| 166 | + return AVERROR_INVALIDDATA; |
| 167 | + } |
| 168 | + |
| 169 | + *got_frame_ptr = 1; |
| 170 | + |
| 171 | + return bytestream2_tell(gb); |
| 172 | +} |
| 173 | + |
| 174 | +const FFCodec ff_misc4_decoder = { |
| 175 | + .p.name = "misc4", |
| 176 | + CODEC_LONG_NAME("Micronas SC-4 Audio"), |
| 177 | + .p.type = AVMEDIA_TYPE_AUDIO, |
| 178 | + .p.id = AV_CODEC_ID_MISC4, |
| 179 | + .priv_data_size = sizeof(MISC4Context), |
| 180 | + .init = misc4_init, |
| 181 | + FF_CODEC_DECODE_CB(misc4_decode), |
| 182 | + .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_SUBFRAMES | |
| 183 | + AV_CODEC_CAP_CHANNEL_CONF, |
| 184 | + .p.sample_fmts = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_S16, |
| 185 | + AV_SAMPLE_FMT_NONE }, |
| 186 | +}; |