$ <feed> | ffmpeg \
                -probesize 50 -analyzeduration 1000 -r 20 -i - \
                -f alsa -ar $ar -ac 1 -itsoffset 1 -probesize 50 -analyzeduration 1000 -i btheadset \
                -c:v copy -r $fps -vsync 1 \
                -c:a libfdk_aac -afterburner 0 -async 2 -ar 48000 -ac 1 -b:a 48k \
                -tune zerolatency -bufsize $((bw*2)) \
                -rtmp_buffer 100 -rtmp_live live \
                -flags +global_header+low_delay \
                -f flv rtmp://*****************


$ cam_rpi
ffmpeg version git-2014-10-17-bbd8c85 Copyright (c) 2000-2014 the FFmpeg developers
  built on Oct 25 2014 19:37:51 with gcc 4.7.1 (crosstool-NG 1.15.2) 20120402 (prerelease)
  configuration: --enable-cross-compile --cross-prefix=/opt/tools/arm-bcm2708/arm-bcm2708hardfp-linux-gnueabi/bin/arm-bcm2708hardfp-linux-gnueabi- --arch=armel --target-os=linux --prefix=/home/david/built_ffmpeg/ --enable-gpl --enable-libx264 --enable-nonfree --enable-libfdk_aac --extra-cflags='-I/home/david/built_ffmpeg/include -O3 -march=armv6zk -mfpu=vfp -mfloat-abi=hard' --extra-ldflags=-L/home/david/built_ffmpeg/lib --extra-libs=-ldl
  libavutil      54. 10.100 / 54. 10.100
  libavcodec     56.  8.100 / 56.  8.100
  libavformat    56.  9.100 / 56.  9.100
  libavdevice    56.  1.100 / 56.  1.100
  libavfilter     5.  1.106 /  5.  1.106
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
[h264 @ 0x15bdd50] Stream #0: not enough frames to estimate rate; consider increasing probesize
[h264 @ 0x15bdd50] decoding for stream 0 failed
Input #0, h264, from 'pipe:':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: h264 (High), yuv420p, 1280x720, 25 tbr, 1200k tbn, 50 tbc
Guessed Channel Layout for  Input Stream #1.0 : mono
Input #1, alsa, from 'btheadset':
  Duration: N/A, start: 1414563845.956580, bitrate: 128 kb/s
    Stream #1:0: Audio: pcm_s16le, 8000 Hz, 1 channels, s16, 128 kb/s
-async is forwarded to lavfi similarly to -af aresample=async=2:min_hard_comp=0.100000:first_pts=0.
Output #0, flv, to 'rtmp://especificos.com.ar:1935/xorg/movie':
  Metadata:
    encoder         : Lavf56.9.100
    Stream #0:0: Video: h264 ([7][0][0][0] / 0x0007), yuv420p, 1280x720, q=2-31, 1k tbn, 20 tbc
    Stream #0:1: Audio: aac (libfdk_aac) ([10][0][0][0] / 0x000A), 48000 Hz, mono, s16, 48 kb/s
    Metadata:
      encoder         : Lavc56.8.100 libfdk_aac
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #1:0 -> #0:1 (pcm_s16le (native) -> aac (libfdk_aac))
frame=13895 fps= 20 q=-1.0 size=   81100kB time=00:11:24.48 bitrate= 970.6kbits/s