| /* |
| * DFPWM encoder |
| * Copyright (c) 2022 Jack Bruienne |
| * Copyright (c) 2012, 2016 Ben "GreaseMonkey" Russell |
| * |
| * 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 |
| */ |
| |
| /** |
| * @file |
| * DFPWM1a encoder |
| */ |
| |
| #include "libavutil/internal.h" |
| #include "avcodec.h" |
| #include "codec_id.h" |
| #include "codec_internal.h" |
| #include "encode.h" |
| |
| typedef struct { |
| int fq, q, s, lt; |
| } DFPWMState; |
| |
| // DFPWM codec from https://github.com/ChenThread/dfpwm/blob/master/1a/ |
| // Licensed in the public domain |
| |
| // note, len denotes how many compressed bytes there are (uncompressed bytes / 8). |
| static void au_compress(DFPWMState *state, int len, uint8_t *outbuf, const uint8_t *inbuf) |
| { |
| unsigned d = 0; |
| for (int i = 0; i < len; i++) { |
| for (int j = 0; j < 8; j++) { |
| int nq, st, ns; |
| // get sample |
| int v = *(inbuf++) - 128; |
| // set bit / target |
| int t = (v > state->q || (v == state->q && v == 127) ? 127 : -128); |
| d >>= 1; |
| if(t > 0) |
| d |= 0x80; |
| |
| // adjust charge |
| nq = state->q + ((state->s * (t-state->q) + 512)>>10); |
| if(nq == state->q && nq != t) |
| nq += (t == 127 ? 1 : -1); |
| state->q = nq; |
| |
| // adjust strength |
| st = (t != state->lt ? 0 : 1023); |
| ns = state->s; |
| if(ns != st) |
| ns += (st != 0 ? 1 : -1); |
| if(ns < 8) ns = 8; |
| state->s = ns; |
| |
| state->lt = t; |
| } |
| |
| // output bits |
| *(outbuf++) = d; |
| } |
| } |
| |
| static av_cold int dfpwm_enc_init(struct AVCodecContext *ctx) |
| { |
| DFPWMState *state = ctx->priv_data; |
| |
| state->fq = 0; |
| state->q = 0; |
| state->s = 0; |
| state->lt = -128; |
| |
| ctx->bits_per_coded_sample = 1; |
| |
| return 0; |
| } |
| |
| static int dfpwm_enc_frame(struct AVCodecContext *ctx, struct AVPacket *packet, |
| const struct AVFrame *frame, int *got_packet) |
| { |
| DFPWMState *state = ctx->priv_data; |
| int size = frame->nb_samples * frame->ch_layout.nb_channels / 8 + (frame->nb_samples % 8 > 0 ? 1 : 0); |
| int ret = ff_get_encode_buffer(ctx, packet, size, 0); |
| |
| if (ret) { |
| *got_packet = 0; |
| return ret; |
| } |
| |
| au_compress(state, size, packet->data, frame->data[0]); |
| |
| *got_packet = 1; |
| return 0; |
| } |
| |
| const FFCodec ff_dfpwm_encoder = { |
| .p.name = "dfpwm", |
| CODEC_LONG_NAME("DFPWM1a audio"), |
| .p.type = AVMEDIA_TYPE_AUDIO, |
| .p.id = AV_CODEC_ID_DFPWM, |
| .priv_data_size = sizeof(DFPWMState), |
| .init = dfpwm_enc_init, |
| FF_CODEC_ENCODE_CB(dfpwm_enc_frame), |
| .p.sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_U8, AV_SAMPLE_FMT_NONE}, |
| .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_VARIABLE_FRAME_SIZE | |
| AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE, |
| }; |