func: static int mxf_read_header(AVFormatContext *s, AVFormatParameters *ap)
  
  {
  
      MXFContext *mxf = s->priv_data;
  
      KLVPacket klv;
  
      int64_t essence_offset = 0;
  
  
  
      mxf->last_forward_tell = INT64_MAX;
  
  
  
      if (!mxf_read_sync(s->pb, mxf_header_partition_pack_key, 14)) {
  
          av_log(s, AV_LOG_ERROR, "could not find header partition pack key\n");
  
          return AVERROR_INVALIDDATA;
  
      }
  
      avio_seek(s->pb, -14, SEEK_CUR);
  
      mxf->fc = s;
  
      mxf->run_in = avio_tell(s->pb);
  
  
  
      while (!s->pb->eof_reached) {
  
          const MXFMetadataReadTableEntry *metadata;
  
  
  
          if (klv_read_packet(&klv, s->pb) < 0) {
  
              /* EOF - seek to previous partition or stop */
  
              if(mxf_parse_handle_partition_or_eof(mxf) <= 0)
  
                  break;
  
              else
  
                  continue;
  
          }
  
  
  
          PRINT_KEY(s, "read header", klv.key);
  
          av_dlog(s, "size %"PRIu64" offset %#"PRIx64"\n", klv.length, klv.offset);
  
          if (IS_KLV_KEY(klv.key, mxf_encrypted_triplet_key) ||
  
              IS_KLV_KEY(klv.key, mxf_essence_element_key) ||
  
              IS_KLV_KEY(klv.key, mxf_avid_essence_element_key) ||
  
              IS_KLV_KEY(klv.key, mxf_system_item_key)) {
  
              if (!mxf->current_partition->essence_offset) {
  
                  compute_partition_essence_offset(s, mxf, &klv);
  
              }
  
  
  
              if (!essence_offset)
  
                  essence_offset = klv.offset;
  
  
  
              /* seek to footer, previous partition or stop */
  
              if (mxf_parse_handle_essence(mxf) <= 0)
  
                  break;
  
              continue;
  
          } else if (!memcmp(klv.key, mxf_header_partition_pack_key, 13) &&
  
                     klv.key[13] >= 2 && klv.key[13] <= 4 && mxf->current_partition) {
  
              /* next partition pack - keep going, seek to previous partition or stop */
  
              if(mxf_parse_handle_partition_or_eof(mxf) <= 0)
  
                  break;
  
          }
  
  
  
          for (metadata = mxf_metadata_read_table; metadata->read; metadata++) {
  
              if (IS_KLV_KEY(klv.key, metadata->key)) {
  
                  int res;
  
                  if (klv.key[5] == 0x53) {
  
                      res = mxf_read_local_tags(mxf, &klv, metadata->read, metadata->ctx_size, metadata->type);
  
                  } else {
  
                      uint64_t next = avio_tell(s->pb) + klv.length;
  
                      res = metadata->read(mxf, s->pb, 0, klv.length, klv.key, klv.offset);
  
                      avio_seek(s->pb, next, SEEK_SET);
  
                  }
  
                  if (res < 0) {
  
                      av_log(s, AV_LOG_ERROR, "error reading header metadata\n");
  
                      return res;
  
                  }
  
                  break;
  
              }
  
          }
  
          if (!metadata->read)
  
              avio_skip(s->pb, klv.length);
  
      }
  
      /* FIXME avoid seek */
  
      if (!essence_offset)  {
  
          av_log(s, AV_LOG_ERROR, "no essence\n");
  
          return AVERROR_INVALIDDATA;
  
      }
  
      avio_seek(s->pb, essence_offset, SEEK_SET);
  
  
  
      mxf_compute_essence_containers(mxf);
  
  
  
      return mxf_parse_structural_metadata(mxf);
  
  }
  