D101101,
$ avconv -i test.mp3 -c:a copy -ss 60 -t 30 out.mp3
avconv version 9.18-6:9.18-0ubuntu0.14.04.1, Copyright (c) 2000-2014 the Libav developers
built on Mar 16 2015 13:20:58 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
[aac @ 0x966fb80] get_buffer() failed
[aac @ 0x966dd40] max_analyze_duration reached
[aac @ 0x966dd40] Estimating duration from bitrate, this may be inaccurate
Input #0, aac, from 'test.mp3':
Duration: 00:04:00.22, bitrate: 30 kb/s
Stream #0.0: Audio: aac, 44100 Hz, stereo, fltp, 30 kb/s
[mp3 @ 0x966e480] Invalid audio stream. Exactly one MP3 audio stream is required.
Output #0, mp3, to 'out.mp3':
Metadata:
encoder : Lavf54.20.4
Stream #0.0: Audio: aac, 44100 Hz, stereo, 30 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument
$ mediainfo test.mp3
General
Complete name : test.mp3
Format : ADTS
Format/Info : Audio Data Transport Stream
File size : 884 KiB
Overall bit rate mode : Variable
Audio
Format : AAC
Format/Info : Advanced Audio Codec
Format version : Version 2
Format profile : HE-AACv2 / HE-AAC / LC
Bit rate mode : Variable
Bit rate : 31.2 Kbps
Channel(s) : 2 channels / 1 channel / 1 channel
Channel positions : Front: L R / Front: C / Front: C
Sampling rate : 44.1 KHz / 44.1 KHz / 22.05 KHz
Compression mode : Lossy
Stream size : 884 KiB (100%)