无法使用 ffmpeg 从视频中提取 mp3 音频

Question

我的输入是 .mp4 视频文件。

尝试#1

ffmpeg -i pipe:0 -y -map a media/73.mp3

错误：

ffmpeg version 3.3.3 Copyright (c) 2000-2017 the FFmpeg developers
  built with Apple LLVM version 8.1.0 (clang-802.0.42)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/3.3.3 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libmp3lame --enable-libx264 --enable-libxvid --enable-opencl --enable-videotoolbox --disable-lzma --enable-vda
  libavutil      55. 58.100 / 55. 58.100
  libavcodec     57. 89.100 / 57. 89.100
  libavformat    57. 71.100 / 57. 71.100
  libavdevice    57.  6.100 / 57.  6.100
  libavfilter     6. 82.100 /  6. 82.100
  libavresample   3.  5.  0 /  3.  5.  0
  libswscale      4.  6.100 /  4.  6.100
  libswresample   2.  7.100 /  2.  7.100
  libpostproc    54.  5.100 / 54.  5.100
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f977d800000] stream 1, offset 0xa8: partial file
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f977d800000] Could not find codec parameters for stream 0 (Video: h264 (avc1 / 0x31637661), none(smpte170m/smpte170m/bt709), 320x176, 300 kb/s): unspecified pixel format
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'pipe:0':
  Metadata:
major_brand     : mp42
minor_version   : 0
compatible_brands: mp42isomavc1
creation_time   : 2012-03-13T08:58:06.000000Z
encoder         : HandBrake 0.9.6 2012022800
  Duration: 00:00:10.03, bitrate: N/A
Stream #0:0(und): Video: h264 (avc1 / 0x31637661), none(smpte170m/smpte170m/bt709), 320x176, 300 kb/s, 25 fps, 25 tbr, 90k tbn, 180k tbc (default)
Metadata:
creation_time   : 2012-03-13T08:58:06.000000Z
  encoder         : JVT/AVC Coding
Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 160 kb/s (default)
Metadata:
  creation_time   : 2012-03-13T08:58:06.000000Z
Stream #0:2(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 160 kb/s
Metadata:
  creation_time   : 2012-03-13T08:58:06.000000Z
Stream #0:3(und): Subtitle: mov_text (text / 0x74786574), 0 kb/s
Metadata:
  creation_time   : 2012-03-13T08:58:06.000000Z
Stream mapping:
  Stream #0:1 -> #0:0 (aac (native) -> mp3 (libmp3lame))
  Stream #0:2 -> #0:1 (aac (native) -> mp3 (libmp3lame))
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f977d800000] stream 1, offset 0xa8: partial file
pipe:0: Invalid data found when processing input
Finishing stream 0:0 without any data written to it.
Finishing stream 0:1 without any data written to it.
[mp3 @ 0x7f977b846800] Invalid audio stream. Exactly one MP3 audio stream is required.
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument
Error initializing output stream 0:1 -- 
Conversion failed!

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尝试#2

ffmpeg -i pipe:0 -y -vn -acodec copy media/72.mp3

错误：

[...]
[mp3 @ 0x7febed835200] Invalid audio stream. Exactly one MP3 audio stream is required.
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument

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尝试#3

ffmpeg -i pipe:0 -y -codec:a libmp3lame -qscale:a 2 media/74.mp3

没有错误ffmpeg，但文件无效（其大小为 334 字节）

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尝试#4

ffmpeg -i pipe:0 -y -vn -acodec mp3 media/78.mp3

没有错误ffmpeg，但文件无效（其大小为 334 字节）

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尝试#5

ffmpeg -f mp4 -i pipe:0 -y media/80.mp3

没有错误ffmpeg，但文件无效（其大小为 334 字节）

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我究竟做错了什么？这似乎是一件相当容易做到的事情......

Answer 1

尝试提取.mp3：

ffmpeg -i video.mp4 -map 0:a -acodec libmp3lame out.mp3

也许这对于提取有用.m4a：

ffmpeg -i video.mp4 -map 0:a -c copy out.m4a