ffmpeg可以提取隐藏字幕数据吗 [英] Can ffmpeg extract closed caption data

问题描述

我目前正在使用ffmpeg将各种格式的视频转换为flv文件.还提出了一个请求，那就是也从文件中获取隐藏字幕信息.有没有人对此有任何经验或知道可以做到这一点?我看不到任何选择，但想问一问.

I am currently using ffmpeg to convert videos in various formats to flv files. One request has also come up and that is to get closed caption info out o the file as well. Does anyone have any experience with this or know it can even be done. I don't see any options for it but thought I would ask and see.

推荐答案

如果像我这样的人最后出现在此线程上，这是对我有用的ffmpeg命令的更详细的说明.

If anyone, like me, ends up on this thread, here's a bit more detailed explanation on ffmpeg command that worked for me.

ffmpeg -f lavfi -i movie=input.ts[out+subcc]  -map 0:1  output.srt

似乎对源的硬性要求是mpegts格式(文件扩展名.ts).否则，lavfi过滤器似乎不起作用.规范out+subcc强制ffmpeg将隐藏式字幕(嵌入到帧数据中)视为单独的流.后来-map 0:1使ffmpeg仅映射该流，并丢弃其他所有内容.结果保存到output.srt.根据您的输入，映射可能会有所不同.找出隐藏字幕映射的一种简单方法是像这样运行ffprobe命令

There seems a hard requirement on source to be of mpegts format (file extension .ts). Otherwise the lavfi filter does not seem to work. The spec out+subcc forces ffmpeg to treat closed captions (which are embedded into frame data) as separate stream. Later -map 0:1 makes ffmpeg map only that stream and discard everything else. Result is saved to output.srt. Depending on your input the mapping might be different. One easy way to figure out the closed captions mapping is to run ffprobe command, like so

$ ffprobe -f lavfi -i movie=input.ts[out+subcc]
ffprobe version N-79653-g4efd3ec Copyright (c) 2007-2016 the FFmpeg developers
  libavutil      55. 22.101 / 55. 22.101
  libavcodec     57. 38.100 / 57. 38.100
  libavformat    57. 34.103 / 57. 34.103
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 44.100 /  6. 44.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
[h264 @ 0x7fe869826200] Increasing reorder buffer to 1
Input #0, lavfi, from 'movie=input.ts[out+subcc]':
  Duration: N/A, start: 1562.233011, bitrate: N/A
    Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 90k fps, 30 tbr, 90k tbn
    Stream #0:1: Subtitle: eia_608

流Subtitle: eia_608具有索引" 0:1，因此应进行映射.

Stream Subtitle: eia_608 has "index" 0:1, so that is what should be mapped.

很少有分开的注释，对于ffmpeg来说，参数顺序很重要，-f lavfi必须在-i move=...之前，否则规格将无法识别.另外，此功能是最近才推出的，因此请仔细检查您的ffmpeg版本并根据需要进行升级.

Few parting notes, order of arguments matters for ffmpeg, -f lavfi must go before -i move=..., otherwise the spec will not be recognized. Also this feature is pretty recent, so double check your ffmpeg version and upgrade if needed.

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