bash – avconv：保存元数据的flac转换为ogg

我正在编写一个命令行工具,将具有各种格式的输入音乐库(flac / ogg / mp3 / …)转换为给定格式的输出音乐库(flac / ogg / mp3).我将它基于avconv(或ffmpeg,如果avconv不可用),因为它是我发现的最完整的命令行转换器.我的脚本可从此URL( GitHub)获得：

https://github.com/biapy/howto.biapy.com/blob/master/various/mussync-tools

我正在尝试将元数据从输入库文件传递到输出/转换的库文件.

我想出了这段代码：

local MAP_METADATA=' 0:g'
  # Specific needs for some input formats/
  case "${INPUT_FILE_MIMETYPE}" in
    'application/ogg' )
      # Get input metadata from first audio stream and direct it to global.
      MAP_METADATA=' 0:s:0'
      ;;

    * )
      # Do nothing.
      # MAP_METADATA=' 0:g'
      ;;
  esac

  # Specific needs for some output formats/
  local OUTPUT_OPTIONS=""
  case "${OUTPUT_FORMAT}" in
    'flac' )
      # No encoding options needed.
      ENCODING_OPTIONS=""
      ;;

    'ogg' )
      # Set vorbis as default codec for ogg.
      OUTPUT_OPTIONS="-codec:a libvorbis -f ${OUTPUT_FORMAT}"
      # Map input metadata to all audio streams in ogg container.
      MAP_METADATA=":s:a ${MAP_METADATA}"
      ;;

    * )
      # Do nothing.
      # MAP_METADATA="${MAP_METADATA}"
      OUTPUT_OPTIONS="-f ${OUTPUT_FORMAT}"
      ;;
  esac

  # Dangerous solution for mp3 cbr format:
  # Write output on pipe and then directed to file.
  # For cbr format for mp3 files. Harmless for other formats.
  # See: http://ffmpeg.zeranoe.com/forum/viewtopic.php?f=7&t=377
  #
  # What about log output ? how to prevent it from being included in
  # the resulting output file ?

  if ! command ${AVCONV} -i "${INPUT_FILE}" 
             -vn -sn 
            -map_metadata${MAP_METADATA} 
            -loglevel "${LOG_LEVEL}" 
            ${AVCONV_OPTIONS} 
            ${OUTPUT_OPTIONS} 
            ${ENCODING_OPTIONS} 
            "${OUTPUT_TEMP_FILE}"; then
    test "${QUIET}" != 'True' && echo "Failed."
    test -e "${OUTPUT_TEMP_FILE}" && command rm "${OUTPUT_TEMP_FILE}"

    return 1
  else
    test "${QUIET}" != 'True' && echo "Done."

    # Test if fix for MP3 VBR is needed.
    # See: http://ffmpeg.zeranoe.com/forum/viewtopic.php?f=7&t=377
    if [ "${OUTPUT_FORMAT}" = 'mp3' -a "${ENCODING_MODE}" != 'CBR' ]; then
      # Output file is MP3 and VBR. Apply header fix.
      if [ "${VERBOSE}" = 'True' ]; then
        command vbrfix "${OUTPUT_TEMP_FILE}" "${OUTPUT_FILE}"
      else
        command vbrfix "${OUTPUT_TEMP_FILE}" "${OUTPUT_FILE}"
      fi
    else
      # Nothing to do but rename the file.
      command mv "${OUTPUT_TEMP_FILE}" "${OUTPUT_FILE}"
    fi

    # Delete temporary file if it is still present.
    test -e "${OUTPUT_TEMP_FILE}" && command rm "${OUTPUT_TEMP_FILE}"

    # Fetch cover art from input file.
    transfert_images "${INPUT_FILE}" "${OUTPUT_FILE}"
  fi

我的问题是,当使用Ubuntu 13.10 Saucy Salamander上提供的avconv版本将flac转换为ogg时,尽管有此选项(将输入flac文件中的全局元数据复制到输出ogg文件的所有音频流),但不保留元数据：

--map_metadata:s:a 0:g

您是否有人知道正确的–map_metadata选项,用于在转换时将元数据从flac输入文件复制到ogg输出文件？

ps：附加问题：如何防止avconv生成的CBR mp3文件有VBR标头？

pps：我知道甜菜等工具,但我还没有看到专门的命令行工具来完成这项任务.