func: int swr_init(struct SwrContext *s){
  
      s->in_buffer_index= 0;
  
      s->in_buffer_count= 0;
  
      s->resample_in_constraint= 0;
  
      free_temp(&s->postin);
  
      free_temp(&s->midbuf);
  
      free_temp(&s->preout);
  
      free_temp(&s->in_buffer);
  
      free_temp(&s->dither);
  
      swri_audio_convert_free(&s-> in_convert);
  
      swri_audio_convert_free(&s->out_convert);
  
      swri_audio_convert_free(&s->full_convert);
  
      swri_rematrix_free(s);
  
  
  
      s->flushed = 0;
  
  
  
      if(s-> in_sample_fmt >= AV_SAMPLE_FMT_NB){
  
          av_log(s, AV_LOG_ERROR, "Requested input sample format %d is invalid\n", s->in_sample_fmt);
  
          return AVERROR(EINVAL);
  
      }
  
      if(s->out_sample_fmt >= AV_SAMPLE_FMT_NB){
  
          av_log(s, AV_LOG_ERROR, "Requested output sample format %d is invalid\n", s->out_sample_fmt);
  
          return AVERROR(EINVAL);
  
      }
  
  
  
      //FIXME should we allow/support using FLT on material that doesnt need it ?
  
      if(av_get_planar_sample_fmt(s->in_sample_fmt) <= AV_SAMPLE_FMT_S16P || s->int_sample_fmt==AV_SAMPLE_FMT_S16P){
  
          s->int_sample_fmt= AV_SAMPLE_FMT_S16P;
  
      }else
  
          s->int_sample_fmt= AV_SAMPLE_FMT_FLTP;
  
  
  
      if(   s->int_sample_fmt != AV_SAMPLE_FMT_S16P
  
          &&s->int_sample_fmt != AV_SAMPLE_FMT_S32P
  
          &&s->int_sample_fmt != AV_SAMPLE_FMT_FLTP){
  
          av_log(s, AV_LOG_ERROR, "Requested sample format %s is not supported internally, S16/S32/FLT is supported\n", av_get_sample_fmt_name(s->int_sample_fmt));
  
          return AVERROR(EINVAL);
  
      }
  
  
  
      set_audiodata_fmt(&s-> in, s-> in_sample_fmt);
  
      set_audiodata_fmt(&s->out, s->out_sample_fmt);
  
  
  
      if (s->out_sample_rate!=s->in_sample_rate || (s->flags & SWR_FLAG_RESAMPLE)){
  
          s->resample = swri_resample_init(s->resample, s->out_sample_rate, s->in_sample_rate, s->filter_size, s->phase_shift, s->linear_interp, s->cutoff, s->int_sample_fmt);
  
      }else
  
          swri_resample_free(&s->resample);
  
      if(    s->int_sample_fmt != AV_SAMPLE_FMT_S16P
  
          && s->int_sample_fmt != AV_SAMPLE_FMT_S32P
  
          && s->int_sample_fmt != AV_SAMPLE_FMT_FLTP
  
          && s->resample){
  
          av_log(s, AV_LOG_ERROR, "Resampling only supported with internal s16/s32/flt\n");
  
          return -1;
  
      }
  
  
  
      if(!s->used_ch_count)
  
          s->used_ch_count= s->in.ch_count;
  
  
  
      if(s->used_ch_count && s-> in_ch_layout && s->used_ch_count != av_get_channel_layout_nb_channels(s-> in_ch_layout)){
  
          av_log(s, AV_LOG_WARNING, "Input channel layout has a different number of channels than the number of used channels, ignoring layout\n");
  
          s-> in_ch_layout= 0;
  
      }
  
  
  
      if(!s-> in_ch_layout)
  
          s-> in_ch_layout= av_get_default_channel_layout(s->used_ch_count);
  
      if(!s->out_ch_layout)
  
          s->out_ch_layout= av_get_default_channel_layout(s->out.ch_count);
  
  
  
      s->rematrix= s->out_ch_layout  !=s->in_ch_layout || s->rematrix_volume!=1.0 ||
  
                   s->rematrix_custom;
  
  
  
  #define RSC 1 //FIXME finetune
  
      if(!s-> in.ch_count)
  
          s-> in.ch_count= av_get_channel_layout_nb_channels(s-> in_ch_layout);
  
      if(!s->used_ch_count)
  
          s->used_ch_count= s->in.ch_count;
  
      if(!s->out.ch_count)
  
          s->out.ch_count= av_get_channel_layout_nb_channels(s->out_ch_layout);
  
  
  
      if(!s-> in.ch_count){
  
          av_assert0(!s->in_ch_layout);
  
          av_log(s, AV_LOG_ERROR, "Input channel count and layout are unset\n");
  
          return -1;
  
      }
  
  
  
      if ((!s->out_ch_layout || !s->in_ch_layout) && s->used_ch_count != s->out.ch_count && !s->rematrix_custom) {
  
          av_log(s, AV_LOG_ERROR, "Rematrix is needed but there is not enough information to do it\n");
  
          return -1;
  
      }
  
  
  
  av_assert0(s->used_ch_count);
  
  av_assert0(s->out.ch_count);
  
      s->resample_first= RSC*s->out.ch_count/s->in.ch_count - RSC < s->out_sample_rate/(float)s-> in_sample_rate - 1.0;
  
  
  
      s->in_buffer= s->in;
  
  
  
      if(!s->resample && !s->rematrix && !s->channel_map && !s->dither_method){
  
          s->full_convert = swri_audio_convert_alloc(s->out_sample_fmt,
  
                                                     s-> in_sample_fmt, s-> in.ch_count, NULL, 0);
  
          return 0;
  
      }
  
  
  
      s->in_convert = swri_audio_convert_alloc(s->int_sample_fmt,
  
                                               s-> in_sample_fmt, s->used_ch_count, s->channel_map, 0);
  
      s->out_convert= swri_audio_convert_alloc(s->out_sample_fmt,
  
                                               s->int_sample_fmt, s->out.ch_count, NULL, 0);
  
  
  
  
  
      s->postin= s->in;
  
      s->preout= s->out;
  
      s->midbuf= s->in;
  
  
  
      if(s->channel_map){
  
          s->postin.ch_count=
  
          s->midbuf.ch_count= s->used_ch_count;
  
          if(s->resample)
  
              s->in_buffer.ch_count= s->used_ch_count;
  
      }
  
      if(!s->resample_first){
  
          s->midbuf.ch_count= s->out.ch_count;
  
          if(s->resample)
  
              s->in_buffer.ch_count = s->out.ch_count;
  
      }
  
  
  
      set_audiodata_fmt(&s->postin, s->int_sample_fmt);
  
      set_audiodata_fmt(&s->midbuf, s->int_sample_fmt);
  
      set_audiodata_fmt(&s->preout, s->int_sample_fmt);
  
  
  
      if(s->resample){
  
          set_audiodata_fmt(&s->in_buffer, s->int_sample_fmt);
  
      }
  
  
  
      s->dither = s->preout;
  
  
  
      if(s->rematrix || s->dither_method)
  
          return swri_rematrix_init(s);
  
  
  
      return 0;
  
  }
  