我在ffmpeg：
上使用此命令/usr/local/bin/ffmpeg -ss 40 -t 40 -i mymusic.mp3 -ab 15 voice.mp3 2>&1
但我看到了这个错误：
Automatic encoder selection failed for output stream #0:0. Default encoder for format mp3 (codec png) is probably disabled. Please choose an encoder manually. Error selecting an encoder for stream 0:0
另外lamemp3已安装并启用，我该如何解决？
这是完整的输出：
ffmpeg version N-81842-g0fbd423 Copyright (c) 2000-2016 the FFmpeg developers
built with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-17)
configuration: --enable-decoder=png --enable-encoder=png
libavutil 55. 32.100 / 55. 32.100
libavcodec 57. 60.101 / 57. 60.101
libavformat 57. 51.102 / 57. 51.102
libavdevice 57. 0.102 / 57. 0.102
libavfilter 6. 63.100 / 6. 63.100
libswscale 4. 1.100 / 4. 1.100
libswresample 2. 2.100 / 2. 2.100
[mp3 @ 0x3ccd3c0] Estimating duration from bitrate, this may be inaccurate
Input #0, mp3, from 'mymusic.mp3':
Metadata:
album_artist : .:.:. WWW.NEWSONG3.COM .:.:.
title : Eshtebah .:.:. WWW.NEWSONG3.COM .:.:.
artist : Abolfazl Fallah .:.:. WWW.NEWSONG3.COM .:.:.
album : .:.:. WWW.NEWSONG3.COM .:.:.
comment : .:.:. WWW.NEWSONG3.COM .:.:.
genre : .:.:. WWW.NEWSONG3.COM .:.:.
track : .:.:. WWW.NEWSONG3.COM .:.:.
copyright : .:.:. WWW.NEWSONG3.COM .:.:.
TOPE : .:.:. WWW.NEWSONG3.COM .:.:.
composer : .:.:. WWW.NEWSONG3.COM .:.:.
TBPM : .:.:. WWW.NEWSONG3.COM .:.:.
TIT3 : .:.:. WWW.NEWSONG3.COM .:.:.
encoded_by : .:.:. WWW.NEWSONG3.COM .:.:.
disc : .:.:. WWW.NEWSONG3.COM .:.:.
MusicMatch_Mood : .:.:. WWW.NEWSONG3.COM .:.:.
date : 2013
Duration: 00:04:08.77, start: 0.000000, bitrate: 129 kb/s
Stream #0:0: Audio: mp3, 48000 Hz, stereo, s16p, 128 kb/s
Stream #0:1: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 300x300 [SAR 96:96 DAR 1:1], 90k tbr, 90k tbn, 90k tbc
Metadata:
comment : Cover (front)
Automatic encoder selection failed for output stream #0:0. Default encoder for format mp3 (codec png) is probably disabled. Please choose an encoder manually.
Error selecting an encoder for stream 0:0