[zhangpengcheng@mobiledev03v ifly]$ /bin/ffmpeg -i test.flv -map 0:a -c copy output.m4a -y
ffmpeg version 3.1.1-static http://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.4.0 (Debian 5.4.0-4) 20160609
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --enable-libmp3lame --enable-libx264 --enable-libx265 --enable-libwebp --enable-libspeex --enable-libvorbis --enable-libvpx --enable-libfreetype --enable-fontconfig --enable-libxvid --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvo-amrwbenc --enable-gray --enable-libopenjpeg --enable-libopus --enable-libass --enable-gnutls --enable-libvidstab --enable-libsoxr --enable-frei0r --enable-libfribidi --disable-indev=sndio --disable-outdev=sndio --enable-librtmp --enable-libmfx --enable-libzimg --cc=gcc
  libavutil      55. 28.100 / 55. 28.100
  libavcodec     57. 48.101 / 57. 48.101
  libavformat    57. 41.100 / 57. 41.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 47.100 /  6. 47.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  1.100 /  2.  1.100
  libpostproc    54.  0.100 / 54.  0.100
[flv @ 0x4cd39c0] video stream discovered after head already parsed
[flv @ 0x4cd39c0] audio stream discovered after head already parsed
Input #0, flv, from 'test.flv':
  Metadata:
    encoder         : Lavf57.41.100
  Duration: 00:06:52.07, start: 0.000000, bitrate: 715 kb/s
    Stream #0:0: Video: h264 (Baseline), yuv420p(tv, smpte170m/bt709/bt709), 668x376, 15 tbr, 1k tbn
    Stream #0:1: Audio: adpcm_swf, 44100 Hz, mono, s16, 176 kb/s
[ipod @ 0x4cd6b20] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
[ipod @ 0x4cd6b20] Could not find tag for codec adpcm_swf in stream #0, codec not currently supported in container
Output #0, ipod, to 'output.m4a':
  Metadata:
    encoder         : Lavf57.41.100
    Stream #0:0: Audio: adpcm_swf, 44100 Hz, mono, 176 kb/s
Stream mapping:
  Stream #0:1 -> #0:0 (copy)
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument