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/* |
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* DFPWM decoder |
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* Copyright (c) 2022 Jack Bruienne |
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* Copyright (c) 2012, 2016 Ben "GreaseMonkey" Russell |
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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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/** |
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* @file |
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* DFPWM1a decoder |
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*/ |
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#include "libavutil/internal.h" |
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#include "avcodec.h" |
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#include "codec_id.h" |
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#include "codec_internal.h" |
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#include "internal.h" |
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typedef struct { |
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int fq, q, s, lt; |
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} DFPWMState; |
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// DFPWM codec from https://github.com/ChenThread/dfpwm/blob/master/1a/ |
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// Licensed in the public domain |
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static void au_decompress(DFPWMState *state, int fs, int len, uint8_t *outbuf, uint8_t *inbuf) |
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{ |
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unsigned d; |
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for (int i = 0; i < len; i++) { |
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// get bits |
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d = *(inbuf++); |
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for (int j = 0; j < 8; j++) { |
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int nq, lq, st, ns, ov; |
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// set target |
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int t = ((d&1) ? 127 : -128); |
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d >>= 1; |
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// adjust charge |
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nq = state->q + ((state->s * (t-state->q) + 512)>>10); |
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if(nq == state->q && nq != t) |
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nq += (t == 127 ? 1 : -1); |
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lq = state->q; |
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state->q = nq; |
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// adjust strength |
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st = (t != state->lt ? 0 : 1023); |
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ns = state->s; |
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if(ns != st) |
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ns += (st != 0 ? 1 : -1); |
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if(ns < 8) ns = 8; |
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state->s = ns; |
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// FILTER: perform antijerk |
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ov = (t != state->lt ? (nq+lq+1)>>1 : nq); |
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// FILTER: perform LPF |
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state->fq += ((fs*(ov-state->fq) + 0x80)>>8); |
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ov = state->fq; |
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// output sample |
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*(outbuf++) = ov + 128; |
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state->lt = t; |
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} |
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} |
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} |
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static av_cold int dfpwm_dec_init(struct AVCodecContext *ctx) |
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{ |
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DFPWMState *state = ctx->priv_data; |
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if (ctx->ch_layout.nb_channels <= 0) { |
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av_log(ctx, AV_LOG_ERROR, "Invalid number of channels\n"); |
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return AVERROR(EINVAL); |
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} |
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state->fq = 0; |
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state->q = 0; |
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state->s = 0; |
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state->lt = -128; |
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ctx->sample_fmt = AV_SAMPLE_FMT_U8; |
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ctx->bits_per_raw_sample = 8; |
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return 0; |
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} |
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static int dfpwm_dec_frame(struct AVCodecContext *ctx, AVFrame *frame, |
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int *got_frame, struct AVPacket *packet) |
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{ |
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DFPWMState *state = ctx->priv_data; |
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int ret; |
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if (packet->size * 8LL % ctx->ch_layout.nb_channels) |
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return AVERROR_PATCHWELCOME; |
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frame->nb_samples = packet->size * 8LL / ctx->ch_layout.nb_channels; |
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if (frame->nb_samples <= 0) { |
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av_log(ctx, AV_LOG_ERROR, "invalid number of samples in packet\n"); |
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return AVERROR_INVALIDDATA; |
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} |
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if ((ret = ff_get_buffer(ctx, frame, 0)) < 0) |
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return ret; |
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au_decompress(state, 140, packet->size, frame->data[0], packet->data); |
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*got_frame = 1; |
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return packet->size; |
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} |
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const FFCodec ff_dfpwm_decoder = { |
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.p.name = "dfpwm", |
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.p.long_name = NULL_IF_CONFIG_SMALL("DFPWM1a audio"), |
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.p.type = AVMEDIA_TYPE_AUDIO, |
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.p.id = AV_CODEC_ID_DFPWM, |
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.priv_data_size = sizeof(DFPWMState), |
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.init = dfpwm_dec_init, |
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FF_CODEC_DECODE_CB(dfpwm_dec_frame), |
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.p.capabilities = AV_CODEC_CAP_DR1, |
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.caps_internal = FF_CODEC_CAP_INIT_THREADSAFE, |
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}; |
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