text: /*
   * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
   *
   * 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
   */
  
  #include "libavutil/common.h"
  #include "libavutil/intreadwrite.h"
  #include "bsf.h"
  #include "bsf_internal.h"
  #include "mpegaudiodecheader.h"
  #include "mpegaudiodata.h"
  
  
  static int mp3_header_decompress(AVBSFContext *ctx, AVPacket *out)
  {
      AVPacket *in;
      uint32_t header;
      int sample_rate= ctx->par_in->sample_rate;
      int sample_rate_index=0;
      int lsf, mpeg25, bitrate_index, frame_size, ret;
      uint8_t *buf;
      int buf_size;
  
      ret = ff_bsf_get_packet(ctx, &in);
      if (ret < 0)
          return ret;
  
      buf      = in->data;
      buf_size = in->size;
  
      header = AV_RB32(buf);
      if(ff_mpa_check_header(header) >= 0){
          av_packet_move_ref(out, in);
          av_packet_free(&in);
  
          return 0;
      }
  
      if(ctx->par_in->extradata_size != 15 || strcmp(ctx->par_in->extradata, "FFCMP3 0.0")){
          av_log(ctx, AV_LOG_ERROR, "Extradata invalid %d\n", ctx->par_in->extradata_size);
          ret = AVERROR(EINVAL);
          goto fail;
      }
  
      header= AV_RB32(ctx->par_in->extradata+11) & MP3_MASK;
  
      lsf     = sample_rate < (24000+32000)/2;
      mpeg25  = sample_rate < (12000+16000)/2;
      sample_rate_index= (header>>10)&3;
      if (sample_rate_index == 3) {
          ret = AVERROR_INVALIDDATA;
          goto fail;
      }
  
      sample_rate= avpriv_mpa_freq_tab[sample_rate_index] >> (lsf + mpeg25); //in case sample rate is a little off
  
      for(bitrate_index=2; bitrate_index<30; bitrate_index++){
          frame_size = avpriv_mpa_bitrate_tab[lsf][2][bitrate_index>>1];
          frame_size = (frame_size * 144000) / (sample_rate << lsf) + (bitrate_index&1);
          if(frame_size == buf_size + 4)
              break;
          if(frame_size == buf_size + 6)
              break;
      }
      if(bitrate_index == 30){
          av_log(ctx, AV_LOG_ERROR, "Could not find bitrate_index.\n");
          ret = AVERROR(EINVAL);
          goto fail;
      }
  
      header |= (bitrate_index&1)<<9;
      header |= (bitrate_index>>1)<<12;
      header |= (frame_size == buf_size + 4)<<16; //FIXME actually set a correct crc instead of 0
  
      ret = av_new_packet(out, frame_size);
      if (ret < 0)
          goto fail;
      ret = av_packet_copy_props(out, in);
      if (ret < 0) {
          av_packet_unref(out);
          goto fail;
      }
      memcpy(out->data + frame_size - buf_size, buf, buf_size + AV_INPUT_BUFFER_PADDING_SIZE);
  
      if(ctx->par_in->channels==2){
          uint8_t *p= out->data + frame_size - buf_size;
          if(lsf){
              FFSWAP(int, p[1], p[2]);
              header |= (p[1] & 0xC0)>>2;
              p[1] &= 0x3F;
          }else{
              header |= p[1] & 0x30;
              p[1] &= 0xCF;
          }
      }
  
      AV_WB32(out->data, header);
  
      ret = 0;
  
  fail:
      av_packet_free(&in);
      return ret;
  }
  
  static const enum AVCodecID codec_ids[] = {
      AV_CODEC_ID_MP3, AV_CODEC_ID_NONE,
  };
  
  const AVBitStreamFilter ff_mp3_header_decompress_bsf = {
      .name      = "mp3decomp",
      .filter    = mp3_header_decompress,
      .codec_ids = codec_ids,
  };
  