pi@raspberrypi:~ $ arecord -Dmic_sv -c2 -r48000 -fS32_LE -twav -d10 | ffmpeg -loglevel debug -i - -acodec libmp3lame -ab 32k -f flv rtmp://209.85.230.23/live2/xbjs-a3gp-0yvk-ftdg
ffmpeg version 3.1.4-static http://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.4.1 (Debian 5.4.1-2) 20160904
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --enable-libmp3lame --enable-libx264 --enable-libwebp --enable-libspeex --enable-libvorbis --enable-libvpx --enable-libfreetype --enable-fontconfig --enable-libxvid --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvo-amrwbenc --enable-gray --enable-libopus --enable-libass --enable-gnutls --enable-libvidstab --enable-libsoxr --enable-frei0r --enable-libfribidi --disable-indev=sndio --disable-outdev=sndio --enable-librtmp --cc=gcc-5 --disable-ffplay
  libavutil      55. 28.100 / 55. 28.100
  libavcodec     57. 48.101 / 57. 48.101
  libavformat    57. 41.100 / 57. 41.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 47.100 /  6. 47.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  1.100 /  2.  1.100
  libpostproc    54.  0.100 / 54.  0.100
Splitting the commandline.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument 'debug'.
Reading option '-i' ... matched as input file with argument '-'.
Reading option '-acodec' ... matched as option 'acodec' (force audio codec ('copy' to copy stream)) with argument 'libmp3lame'.
Reading option '-ab' ... matched as option 'ab' (audio bitrate (please use -b:a)) with argument '32k -f'.
Reading option 'flv' ... matched as output file.
Reading option 'rtmp://209.85.230.23/live2/xbjs-a3gp-0yvk-ftdg' ... matched as output file.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option loglevel (set logging level) with argument debug.
Successfully parsed a group of options.
Parsing a group of options: input file -.
Successfully parsed a group of options.
Opening an input file: -.
[pipe @ 0x276f750] Setting default whitelist 'crypto'
Recording WAVE 'stdin' : Signed 32 bit Little Endian, Rate 48000 Hz, Stereo
[wav @ 0x276f0c0] Format wav probed with size=2048 and score=99
[wav @ 0x276f0c0] Before avformat_find_stream_info() pos: 44 bytes read:80812 seeks:0 nb_streams:1
[wav @ 0x276f0c0] parser not found for codec pcm_s32le, packets or times may be invalid.
    Last message repeated 1 times
[wav @ 0x276f0c0] All info found
[wav @ 0x276f0c0] After avformat_find_stream_info() pos: 204844 bytes read:209580 seeks:0 frames:50
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, wav, from 'pipe:':
  Duration: N/A, bitrate: 3072 kb/s
    Stream #0:0, 50, 1/48000: Audio: pcm_s32le ([1][0][0][0] / 0x0001), 48000 Hz, 2 channels, s32, 3072 kb/s
Successfully opened the file.
Parsing a group of options: output file flv.
Applying option acodec (force audio codec ('copy' to copy stream)) with argument libmp3lame.
Applying option ab (audio bitrate (please use -b:a)) with argument 32k -f.
Successfully parsed a group of options.
Opening an output file: flv.
[NULL @ 0x27af3a0] Unable to find a suitable output format for 'flv'
flv: Invalid argument
[AVIOContext @ 0x27778e0] Statistics: 209580 bytes read, 0 seeks
pi@raspberrypi:~ $