我想将两个音频文件混合为一个使用 ffmpeg。于是我下载了最新版的ffmpeg，查看文档，得到代码：
ffmpeg -i 10001.wav -i 201.wav -filter_complex amix=inputs=2:duration=shortest output.wav
但我收到了这个错误：
ffmpeg version 0.11.1 Copyright (c) 2000-2012 the FFmpeg developers
built on Aug 9 2012 16:22:59 with gcc 4.1.2 20080704 (Red Hat 4.1.2-52)
configuration: --prefix=/usr/ --enable-gpl --enable-libx264 --enable-libmp3lame
libavutil 51. 54.100 / 51. 54.100
libavcodec 54. 23.100 / 54. 23.100
libavformat 54. 6.100 / 54. 6.100
libavdevice 54. 0.100 / 54. 0.100
libavfilter 2. 77.100 / 2. 77.100
libswscale 2. 1.100 / 2. 1.100
libswresample 0. 15.100 / 0. 15.100
libpostproc 52. 0.100 / 52. 0.100
[wav @ 0x13d08100] max_analyze_duration 5000000 reached at 5120000
Guessed Channel Layout for Input Stream #0.0 : mono
Input #0, wav, from '10001.wav':
Duration: 00:00:07.91, bitrate: 64 kb/s
Stream #0:0: Audio: pcm_alaw ([6][0][0][0] / 0x0006), 8000 Hz, mono, s16, 64 kb/s
[wav @ 0x13d08980] max_analyze_duration 5000000 reached at 5120000
Guessed Channel Layout for Input Stream #1.0 : mono
Input #1, wav, from '201.wav':
Duration: 00:00:11.88, bitrate: 128 kb/s
Stream #1:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 8000 Hz, mono, s16, 128 kb/s
[abuffersink @ 0x13d268c0] No opaque field provided, an AVABufferSinkParams struct is required
谁能帮助我？谢谢！