| /* |
| * 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 | |
| #if FF_API_SUBFRAMES |
| AV_CODEC_CAP_SUBFRAMES | |
| #endif |
| AV_CODEC_CAP_CHANNEL_CONF, |
| .p.sample_fmts = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_S16, |
| AV_SAMPLE_FMT_NONE }, |
| }; |