1 /*
2 * DFPWM encoder
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 encoder
26 */
27
28 #include "libavutil/internal.h"
29 #include "avcodec.h"
30 #include "codec_id.h"
31 #include "codec_internal.h"
32 #include "encode.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
41 // note, len denotes how many compressed bytes there are (uncompressed bytes / 8).
au_compress(DFPWMState *state, int len, uint8_t *outbuf, uint8_t *inbuf)42 static void au_compress(DFPWMState *state, int len, uint8_t *outbuf, uint8_t *inbuf)
43 {
44 unsigned d = 0;
45 for (int i = 0; i < len; i++) {
46 for (int j = 0; j < 8; j++) {
47 int nq, st, ns;
48 // get sample
49 int v = *(inbuf++) - 128;
50 // set bit / target
51 int t = (v > state->q || (v == state->q && v == 127) ? 127 : -128);
52 d >>= 1;
53 if(t > 0)
54 d |= 0x80;
55
56 // adjust charge
57 nq = state->q + ((state->s * (t-state->q) + 512)>>10);
58 if(nq == state->q && nq != t)
59 nq += (t == 127 ? 1 : -1);
60 state->q = nq;
61
62 // adjust strength
63 st = (t != state->lt ? 0 : 1023);
64 ns = state->s;
65 if(ns != st)
66 ns += (st != 0 ? 1 : -1);
67 if(ns < 8) ns = 8;
68 state->s = ns;
69
70 state->lt = t;
71 }
72
73 // output bits
74 *(outbuf++) = d;
75 }
76 }
77
dfpwm_enc_init(struct AVCodecContext *ctx)78 static av_cold int dfpwm_enc_init(struct AVCodecContext *ctx)
79 {
80 DFPWMState *state = ctx->priv_data;
81
82 state->fq = 0;
83 state->q = 0;
84 state->s = 0;
85 state->lt = -128;
86
87 ctx->bits_per_coded_sample = 1;
88
89 return 0;
90 }
91
dfpwm_enc_frame(struct AVCodecContext *ctx, struct AVPacket *packet, const struct AVFrame *frame, int *got_packet)92 static int dfpwm_enc_frame(struct AVCodecContext *ctx, struct AVPacket *packet,
93 const struct AVFrame *frame, int *got_packet)
94 {
95 DFPWMState *state = ctx->priv_data;
96 int size = frame->nb_samples * frame->ch_layout.nb_channels / 8 + (frame->nb_samples % 8 > 0 ? 1 : 0);
97 int ret = ff_get_encode_buffer(ctx, packet, size, 0);
98
99 if (ret) {
100 *got_packet = 0;
101 return ret;
102 }
103
104 au_compress(state, size, packet->data, frame->data[0]);
105
106 *got_packet = 1;
107 return 0;
108 }
109
110 const FFCodec ff_dfpwm_encoder = {
111 .p.name = "dfpwm",
112 .p.long_name = NULL_IF_CONFIG_SMALL("DFPWM1a audio"),
113 .p.type = AVMEDIA_TYPE_AUDIO,
114 .p.id = AV_CODEC_ID_DFPWM,
115 .priv_data_size = sizeof(DFPWMState),
116 .init = dfpwm_enc_init,
117 FF_CODEC_ENCODE_CB(dfpwm_enc_frame),
118 .p.sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_U8, AV_SAMPLE_FMT_NONE},
119 .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_VARIABLE_FRAME_SIZE,
120 .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,
121 };
122