mirror of https://github.com/FFmpeg/FFmpeg.git
Paul B Mahol
2 years ago
parent
6df3ad9687
commit
ea93943bee
9 changed files with 200 additions and 1 deletions
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/*
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* Micronas SC-4 audio decoder |
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* Copyright (c) 2022 Paul B Mahol |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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#include "libavutil/internal.h" |
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#include "libavutil/intreadwrite.h" |
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#include "avcodec.h" |
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#include "codec_internal.h" |
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#include "decode.h" |
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#include "bytestream.h" |
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#include "mathops.h" |
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static const int16_t steps[16] = { |
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4084, 18, 41, 64, 112, 198, 355, 1122, |
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1122, 355, 198, 112, 64, 41, 18, 4084, |
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}; |
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static const int16_t diffs[16] = { |
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2048, 4, 135, 213, 273, 323, 373, 425, |
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425, 373, 323, 273, 213, 135, 4, 2048, |
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}; |
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typedef struct ChannelContext { |
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unsigned last_step; |
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int64_t new_pred; |
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int64_t pred; |
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int64_t weights_tab[6]; |
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int32_t diffs_tab[6]; |
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} ChannelContext; |
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typedef struct MISC4Context { |
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GetByteContext gb; |
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uint32_t marker; |
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ChannelContext ch[2]; |
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} MISC4Context; |
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static av_cold int misc4_init(AVCodecContext *avctx) |
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{ |
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MISC4Context *s = avctx->priv_data; |
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avctx->sample_fmt = AV_SAMPLE_FMT_S16; |
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switch (avctx->sample_rate) { |
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case 8000: |
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case 11025: |
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s->marker = 0x11b; |
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break; |
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case 16000: |
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case 32000: |
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s->marker = 0x2b2; |
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break; |
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} |
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return 0; |
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} |
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#define FRACBITS 12 |
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#define WEIGHTSBITS 26 |
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static int64_t prediction(int delta, ChannelContext *c) |
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{ |
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const int isign = FFDIFFSIGN(delta, 0); |
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int64_t dotpr = 0; |
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c->new_pred = delta * (1LL << FRACBITS) + c->pred; |
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for (int i = 0; i < 6; i++) { |
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const int sign = FFSIGN(c->diffs_tab[i]); |
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c->weights_tab[i] = (c->weights_tab[i] * 255LL) / 256; |
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c->weights_tab[i] += (1LL << (WEIGHTSBITS + 1)) * sign * isign; |
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} |
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memmove(&c->diffs_tab[1], &c->diffs_tab[0], 5 * sizeof(int32_t)); |
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c->diffs_tab[0] = -delta * (1 << (FRACBITS-8)); |
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c->pred = c->new_pred; |
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dotpr = 0; |
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for (int i = 0; i < 6; i++) |
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dotpr += ((int64_t)c->diffs_tab[i] * c->weights_tab[i]) >> WEIGHTSBITS; |
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c->pred += dotpr; |
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c->pred = av_clip64(c->pred, -16383 * (1 << FRACBITS), 16383 * (1 << FRACBITS)); |
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c->pred = c->pred * 9 / 10; |
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return c->new_pred; |
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} |
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static int16_t decode(ChannelContext *c, unsigned nibble) |
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{ |
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int diff, diff_sign, adiff = 0, delta; |
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uint32_t step, newstep; |
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int64_t pred; |
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diff_sign = nibble >> 3; |
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diff = diffs[nibble]; |
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step = diff + (c->last_step >> 2); |
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newstep = step & 0xfff; |
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if (newstep >> 11 == 0) |
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adiff = (((step & 0x7f) + 0x80) * 128) >> |
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(14 - (newstep >> 7)); |
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delta = diff_sign ? -adiff : adiff; |
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delta = av_clip_intp2(delta, 15); |
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pred = prediction(delta, c); |
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nibble = steps[nibble]; |
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newstep = nibble * 32 - c->last_step & 0x1ffff; |
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newstep = ((newstep >> 5) + (newstep & 0x10000 ? 0x1000 : 0) + c->last_step) & 0x1fff; |
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c->last_step = av_clip(newstep, 544, 5120); |
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return av_clip_int16(pred >> (FRACBITS - 3)); |
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} |
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static int misc4_decode(AVCodecContext *avctx, AVFrame *frame, |
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int *got_frame_ptr, AVPacket *pkt) |
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{ |
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MISC4Context *s = avctx->priv_data; |
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GetByteContext *gb = &s->gb; |
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uint32_t hdr; |
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int ret; |
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bytestream2_init(gb, pkt->data, pkt->size); |
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frame->nb_samples = 29 * (1 + (avctx->ch_layout.nb_channels == 1)); |
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if ((ret = ff_get_buffer(avctx, frame, 0)) < 0) |
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return ret; |
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hdr = bytestream2_peek_be32(gb); |
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if (hdr == s->marker) { |
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bytestream2_skip(gb, 5); |
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} else if ((hdr >> 16) == s->marker) { |
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bytestream2_skip(gb, 3); |
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} |
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{ |
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int16_t *samples = (int16_t *)frame->data[0]; |
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const int st = avctx->ch_layout.nb_channels == 2; |
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int n; |
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for (n = 0; n < 29; n++) { |
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int nibble = bytestream2_get_byte(gb); |
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samples[2*n+0] = decode(&s->ch[0 ], nibble >> 4); |
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samples[2*n+1] = decode(&s->ch[st], nibble & 15); |
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if (bytestream2_get_bytes_left(gb) <= 0) |
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break; |
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} |
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if (n == 29 && bytestream2_get_byte(gb) != 0x55) |
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return AVERROR_INVALIDDATA; |
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} |
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*got_frame_ptr = 1; |
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return bytestream2_tell(gb); |
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} |
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const FFCodec ff_misc4_decoder = { |
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.p.name = "misc4", |
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CODEC_LONG_NAME("Micronas SC-4 Audio"), |
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.p.type = AVMEDIA_TYPE_AUDIO, |
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.p.id = AV_CODEC_ID_MISC4, |
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.priv_data_size = sizeof(MISC4Context), |
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.init = misc4_init, |
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FF_CODEC_DECODE_CB(misc4_decode), |
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.p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_SUBFRAMES | |
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AV_CODEC_CAP_CHANNEL_CONF, |
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.p.sample_fmts = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_S16, |
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AV_SAMPLE_FMT_NONE }, |
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}; |
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