经过一番工作，我终于能够在Heroku上安装buildpack了。我遇到了这个错误：
Stream #0:0: Audio: pcm_u8 ([1][0][0][0] / 0x0001), 22050 Hz, mono, u8, 176 kb/s
2015-10-03T01:15:59.635036+00:00 app[web.1]: -t is not an input option,
keeping it for the next output; consider fixing your command line.
2015-10-03T01:15:59.635055+00:00 app[web.1]: Please use -q:a or -q:v, -qscale is ambiguous
2015-10-03T01:15:59.635479+00:00 app[web.1]: Unknown encoder 'libvorbis'
我的代码是：
ffmpeg -t 15 -i #{current_path} -acodec libvorbis -qscale 1 #{temp_path}
-t选项应为秒，libvorbis用于ogg转换。
ffmpeg -version会返回此信息：
ffmpeg version git-2013-06-02-5711e4f
built on Jun 2 2013 07:38:40 with gcc 4.4.3 (Ubuntu 4.4.3-4ubuntu5.1)
configuration: --enable-shared --disable-asm --prefix=/app/vendor/ffmpeg
libavutil 52. 34.100 / 52. 34.100 libavcodec 55. 13.100 / 55. 13.100
libavformat 55. 8.102 / 55. 8.102 libavdevice 55. 2.100 / 55. 2.100
libavfilter 3. 74.101 / 3. 74.101 libswscale 2. 3.100 / 2. 3.100
libswresample 0. 17.102 / 0. 17.102
我做错了什么？