1 /*
2 * DFPWM decoder
3 * Copyright (c) 2022 Jack Bruienne
4 * Copyright (c) 2012, 2016 Ben "GreaseMonkey" Russell
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 /**
24 * @file
25 * DFPWM1a decoder
26 */
27
28 #include "libavutil/internal.h"
29 #include "avcodec.h"
30 #include "codec_id.h"
31 #include "codec_internal.h"
32 #include "internal.h"
33
34 typedef struct {
35 int fq, q, s, lt;
36 } DFPWMState;
37
38 // DFPWM codec from https://github.com/ChenThread/dfpwm/blob/master/1a/
39 // Licensed in the public domain
40
au_decompress(DFPWMState * state,int fs,int len,uint8_t * outbuf,const uint8_t * inbuf)41 static void au_decompress(DFPWMState *state, int fs, int len,
42 uint8_t *outbuf, const uint8_t *inbuf)
43 {
44 unsigned d;
45 for (int i = 0; i < len; i++) {
46 // get bits
47 d = *(inbuf++);
48 for (int j = 0; j < 8; j++) {
49 int nq, lq, st, ns, ov;
50 // set target
51 int t = ((d&1) ? 127 : -128);
52 d >>= 1;
53
54 // adjust charge
55 nq = state->q + ((state->s * (t-state->q) + 512)>>10);
56 if(nq == state->q && nq != t)
57 nq += (t == 127 ? 1 : -1);
58 lq = state->q;
59 state->q = nq;
60
61 // adjust strength
62 st = (t != state->lt ? 0 : 1023);
63 ns = state->s;
64 if(ns != st)
65 ns += (st != 0 ? 1 : -1);
66 if(ns < 8) ns = 8;
67 state->s = ns;
68
69 // FILTER: perform antijerk
70 ov = (t != state->lt ? (nq+lq+1)>>1 : nq);
71
72 // FILTER: perform LPF
73 state->fq += ((fs*(ov-state->fq) + 0x80)>>8);
74 ov = state->fq;
75
76 // output sample
77 *(outbuf++) = ov + 128;
78
79 state->lt = t;
80 }
81 }
82 }
83
dfpwm_dec_init(struct AVCodecContext * ctx)84 static av_cold int dfpwm_dec_init(struct AVCodecContext *ctx)
85 {
86 DFPWMState *state = ctx->priv_data;
87
88 if (ctx->ch_layout.nb_channels <= 0) {
89 av_log(ctx, AV_LOG_ERROR, "Invalid number of channels\n");
90 return AVERROR(EINVAL);
91 }
92
93 state->fq = 0;
94 state->q = 0;
95 state->s = 0;
96 state->lt = -128;
97
98 ctx->sample_fmt = AV_SAMPLE_FMT_U8;
99 ctx->bits_per_raw_sample = 8;
100
101 return 0;
102 }
103
dfpwm_dec_frame(struct AVCodecContext * ctx,AVFrame * frame,int * got_frame,struct AVPacket * packet)104 static int dfpwm_dec_frame(struct AVCodecContext *ctx, AVFrame *frame,
105 int *got_frame, struct AVPacket *packet)
106 {
107 DFPWMState *state = ctx->priv_data;
108 int ret;
109
110 if (packet->size * 8LL % ctx->ch_layout.nb_channels)
111 return AVERROR_PATCHWELCOME;
112
113 frame->nb_samples = packet->size * 8LL / ctx->ch_layout.nb_channels;
114 if (frame->nb_samples <= 0) {
115 av_log(ctx, AV_LOG_ERROR, "invalid number of samples in packet\n");
116 return AVERROR_INVALIDDATA;
117 }
118
119 if ((ret = ff_get_buffer(ctx, frame, 0)) < 0)
120 return ret;
121
122 au_decompress(state, 140, packet->size, frame->data[0], packet->data);
123
124 *got_frame = 1;
125 return packet->size;
126 }
127
128 const FFCodec ff_dfpwm_decoder = {
129 .p.name = "dfpwm",
130 .p.long_name = NULL_IF_CONFIG_SMALL("DFPWM1a audio"),
131 .p.type = AVMEDIA_TYPE_AUDIO,
132 .p.id = AV_CODEC_ID_DFPWM,
133 .priv_data_size = sizeof(DFPWMState),
134 .init = dfpwm_dec_init,
135 FF_CODEC_DECODE_CB(dfpwm_dec_frame),
136 .p.capabilities = AV_CODEC_CAP_DR1,
137 .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,
138 };
139