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ffmpeg-4.2.2/libavcodec/dsddec.c 3.79 KB
aac5773f   hucm   功能基本完成,接口待打磨
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  /*
   * Direct Stream Digital (DSD) decoder
   * based on BSD licensed dsd2pcm by Sebastian Gesemann
   * Copyright (c) 2009, 2011 Sebastian Gesemann. All rights reserved.
   * Copyright (c) 2014 Peter Ross
   *
   * 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
   * Direct Stream Digital (DSD) decoder
   */
  
  #include "libavcodec/internal.h"
  #include "libavcodec/mathops.h"
  #include "avcodec.h"
  #include "dsd.h"
  
  #define DSD_SILENCE 0x69
  /* 0x69 = 01101001
   * This pattern "on repeat" makes a low energy 352.8 kHz tone
   * and a high energy 1.0584 MHz tone which should be filtered
   * out completely by any playback system --> silence
   */
  
  static av_cold int decode_init(AVCodecContext *avctx)
  {
      DSDContext * s;
      int i;
      uint8_t silence;
  
      ff_init_dsd_data();
  
      s = av_malloc_array(sizeof(DSDContext), avctx->channels);
      if (!s)
          return AVERROR(ENOMEM);
  
      silence = avctx->codec_id == AV_CODEC_ID_DSD_LSBF || avctx->codec_id == AV_CODEC_ID_DSD_LSBF_PLANAR ? ff_reverse[DSD_SILENCE] : DSD_SILENCE;
      for (i = 0; i < avctx->channels; i++) {
          s[i].pos = 0;
          memset(s[i].buf, silence, sizeof(s[i].buf));
      }
  
      avctx->sample_fmt = AV_SAMPLE_FMT_FLTP;
      avctx->priv_data  = s;
      return 0;
  }
  
  static int decode_frame(AVCodecContext *avctx, void *data,
                          int *got_frame_ptr, AVPacket *avpkt)
  {
      DSDContext * s = avctx->priv_data;
      AVFrame *frame = data;
      int ret, i;
      int lsbf = avctx->codec_id == AV_CODEC_ID_DSD_LSBF || avctx->codec_id == AV_CODEC_ID_DSD_LSBF_PLANAR;
      int src_next;
      int src_stride;
  
      frame->nb_samples = avpkt->size / avctx->channels;
  
      if (avctx->codec_id == AV_CODEC_ID_DSD_LSBF_PLANAR || avctx->codec_id == AV_CODEC_ID_DSD_MSBF_PLANAR) {
          src_next   = frame->nb_samples;
          src_stride = 1;
      } else {
          src_next   = 1;
          src_stride = avctx->channels;
      }
  
      if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
          return ret;
  
      for (i = 0; i < avctx->channels; i++) {
          float * dst = ((float **)frame->extended_data)[i];
          ff_dsd2pcm_translate(&s[i], frame->nb_samples, lsbf,
              avpkt->data + i * src_next, src_stride,
              dst, 1);
      }
  
      *got_frame_ptr = 1;
      return frame->nb_samples * avctx->channels;
  }
  
  #define DSD_DECODER(id_, name_, long_name_) \
  AVCodec ff_##name_##_decoder = { \
      .name         = #name_, \
      .long_name    = NULL_IF_CONFIG_SMALL(long_name_), \
      .type         = AVMEDIA_TYPE_AUDIO, \
      .id           = AV_CODEC_ID_##id_, \
      .init         = decode_init, \
      .decode       = decode_frame, \
      .sample_fmts  = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_FLTP, \
                                                     AV_SAMPLE_FMT_NONE }, \
  };
  
  DSD_DECODER(DSD_LSBF, dsd_lsbf, "DSD (Direct Stream Digital), least significant bit first")
  DSD_DECODER(DSD_MSBF, dsd_msbf, "DSD (Direct Stream Digital), most significant bit first")
  DSD_DECODER(DSD_MSBF_PLANAR, dsd_msbf_planar, "DSD (Direct Stream Digital), most significant bit first, planar")
  DSD_DECODER(DSD_LSBF_PLANAR, dsd_lsbf_planar, "DSD (Direct Stream Digital), least significant bit first, planar")