-f alsa -ac 2 -i pulse output.flac
ffmpeg version git-2013-08-04-61af627 Copyright (c) 2000-2013 the FFmpeg developers
  built on Feb 19 2014 04:33:30 with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-4)
  configuration: --prefix=/mnt/video/ffmpeg/build --extra-cflags=-I/mnt/video/ffmpeg/build/include --extra-ldflags=-L/mnt/video/ffmpeg/build/lib --bindir=/mnt/video/ffmpeg/bin --extra-libs=-ldl --enable-gpl --enable-nonfree --enable-libfdk_aac --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libfreetype --enable-libspeex --enable-libtheora --enable-x11grab
  libavutil      52. 40.100 / 52. 40.100
  libavcodec     55. 20.100 / 55. 20.100
  libavformat    55. 13.101 / 55. 13.101
  libavdevice    55.  3.100 / 55.  3.100
  libavfilter     3. 82.100 /  3. 82.100
  libswscale      2.  4.100 /  2.  4.100
  libswresample   0. 17.103 /  0. 17.103
  libpostproc    52.  3.100 / 52.  3.100
Guessed Channel Layout for  Input Stream #0.0 : stereo
Input #0, alsa, from 'pulse':
  Duration: N/A, start: 1411081041.562795, bitrate: 1536 kb/s
    Stream #0:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
Output #0, flac, to 'output.flac':
  Metadata:
    encoder         : Lavf55.13.101
    Stream #0:0: Audio: flac, 48000 Hz, stereo, s16, 128 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s16le -> flac)
Press [q] to stop, [?] for help
[flac @ 0x2bdfe00] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 878366 >= 877553
[flac @ 0x2bdfe00] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 1060864 >= 1060339
size=    1167kB time=00:00:14.81 bitrate= 645.7kbits/s
video:0kB audio:1159kB subtitle:0 global headers:0kB muxing overhead 0.695229%