[FFmpeg-user] Help with extracting audio from MP4

[Peter]

Hi,

I have seen many examples using ffmpeg to extract the audio from a video. But 
these examples are mostly from other sites (ie.e not the ffmpeg site), and 3 
to 5 years old.  I can't seem to find the documentation from the ffmpeg 
website, on how to use ffmpeg to extract audio from a video file.

Here is the video file ..

----------------
$ ffmpeg -i 16187821_363927127308754_4400528164682465280_n.mp4 
ffmpeg version 2.8.10-0ubuntu0.16.04.1 Copyright (c) 2000-2016 the FFmpeg 
developers
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
  configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-
ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/
include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --
disable-stripping --disable-decoder=libopenjpeg --disable-
decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls 
--enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-
libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-
libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-
libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-
libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-
libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-
libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-
libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi 
--enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-
libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-
libopencv
  libavutil      54. 31.100 / 54. 31.100
  libavcodec     56. 60.100 / 56. 60.100
  libavformat    56. 40.101 / 56. 40.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 40.101 /  5. 40.101
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.101 /  1.  2.101
  libpostproc    53.  3.100 / 53.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 
'16187821_363927127308754_4400528164682465280_n.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.40.101
  Duration: 00:11:16.65, start: 0.000000, bitrate: 576 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 
360x642, 500 kb/s, 29.61 fps, 29.67 tbr, 90k tbn, 59.33 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, 
fltp, 66 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
At least one output file must be specified
--------------------------

If I simply supply an output filename, it results in the codec of MPEG Audio 
Layer 1/2(mpga), sample rate: 48000 Hz and bitrate: 64 kb/s

If I use an example and the code is ..

ffmpeg -i 16187821_363927127308754_4400528164682465280_n.mp4  -b:a 192K -vn 
filename.mp3

.. the file is about 3 times the size and the bitrate is 192 kb/s

Now to my questions:

1. Do I need to change the frame rate or bit rate ?
2. How do I ensure the audio quality is as good as the audio in the video ?
3. Can the audio quality be improved ?

Regards,

Peter