FFMPEG：如何选择没有语言元数据的音频流

我有一些包含一个或多个音频流的源视频文件。
我想用意大利语对每个源文件进行编码。那我就可以做了

ffmpeg -i source-file.avi -c:v ... -c:a ... -map 0:a:m:language:ita ...

但某些源文件的音频流没有语言元数据。
我认为可以将语言元数据设置为“und”特殊值。然后，我尝试使用以下命令选择音频流：

ffmpeg -i source-file.avi -c:v ... -c:a ... -map 0:a:m:language:ita? -map 0:a:m:language:und? ...

（字符对ffmpeg说，如果音频流不存在，他不会触发异常）。
不幸的是，此命令不起作用。。。ffmpeg似乎搜索“und”语言，而不是“不”语言搜索音频流

视频元数据 这是音频流没有语言值的视频元数据：

Input #0, matroska,webm, from 'D:\My-Video.mkv':
  Metadata:
    title           : My-Video
    encoder         : libebml v1.3.3 + libmatroska v1.4.4
    creation_time   : 2016-01-20T16:02:03.000000Z
  Duration: 01:15:28.93, start: 0.000000, bitrate: 2775 kb/s
    Stream #0:0: Video: h264 (High), yuv420p(progressive), 720x576 [SAR 64:45 DAR 16:9], 25 fps, 25 tbr, 1k tbn, 50 tbc (default)
    Metadata:
      BPS             : 2387529
      BPS-eng         : 2387529
      DURATION        : 01:15:28.920000000
      DURATION-eng    : 01:15:28.920000000
      NUMBER_OF_FRAMES: 113223
      NUMBER_OF_FRAMES-eng: 113223
      NUMBER_OF_BYTES : 1351616420
      NUMBER_OF_BYTES-eng: 1351616420
      _STATISTICS_WRITING_APP: mkvmerge v8.7.0 ('All of the above') 64bit
      _STATISTICS_WRITING_APP-eng: mkvmerge v8.7.0 ('All of the above') 64bit
      _STATISTICS_WRITING_DATE_UTC: 2016-01-20 16:02:03
      _STATISTICS_WRITING_DATE_UTC-eng: 2016-01-20 16:02:03
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:1: Audio: ac3, 48000 Hz, 5.1(side), fltp, 384 kb/s (default)
    Metadata:
      BPS             : 384000
      BPS-eng         : 384000
      DURATION        : 01:15:28.928000000
      DURATION-eng    : 01:15:28.928000000
      NUMBER_OF_FRAMES: 141529
      NUMBER_OF_FRAMES-eng: 141529
      NUMBER_OF_BYTES : 217388544
      NUMBER_OF_BYTES-eng: 217388544
      _STATISTICS_WRITING_APP: mkvmerge v8.7.0 ('All of the above') 64bit
      _STATISTICS_WRITING_APP-eng: mkvmerge v8.7.0 ('All of the above') 64bit
      _STATISTICS_WRITING_DATE_UTC: 2016-01-20 16:02:03
      _STATISTICS_WRITING_DATE_UTC-eng: 2016-01-20 16:02:03
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:2(ita): Subtitle: dvd_subtitle, 720x576 (default)
    Metadata:
      BPS             : 2218
      BPS-eng         : 2218
      DURATION        : 01:09:57.232000000
      DURATION-eng    : 01:09:57.232000000
      NUMBER_OF_FRAMES: 965
      NUMBER_OF_FRAMES-eng: 965
      NUMBER_OF_BYTES : 1163769
      NUMBER_OF_BYTES-eng: 1163769
      _STATISTICS_WRITING_APP: mkvmerge v8.7.0 ('All of the above') 64bit
      _STATISTICS_WRITING_APP-eng: mkvmerge v8.7.0 ('All of the above') 64bit
      _STATISTICS_WRITING_DATE_UTC: 2016-01-20 16:02:03
      _STATISTICS_WRITING_DATE_UTC-eng: 2016-01-20 16:02:03
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES

有人能帮我吗？

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谢谢

共享完整日志。@Gyan:full log added共享完整日志。@Gyan:full log added