我尝试使用以下命令将.m4a文件转换为文件：.mp3ffmpeg
$ ffmpeg -i music.m4a music.mp3
不幸的是，我得到了一个零字节大小的文件作为输出返回。命令的输出如下：
FFmpeg version 0.6-4:0.6-2ubuntu6.2, Copyright (c) 2000-2010 the FFmpeg developers
built on Sep 16 2011 17:11:24 with gcc 4.4.5
configuration: --extra-version=4:0.6-2ubuntu6.2 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-vaapi --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
WARNING: library configuration mismatch
libavutil configuration: --extra-version=4:0.6-2ubuntu6.2 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-vaapi --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-x11grab --enable-libdc1394 …