ffmpeg unkown libfaac ubuntu 14.04

Question

I Have Installed ffmpeg 2.3 in Ubuntu 14.04

ffmpeg -i demo.mpg -acodec libfaac demo.mp4
ffmpeg version 2.3 Copyright (c) 2000-2014 the FFmpeg developers
  built on Aug 13 2014 22:15:33 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
  configuration: 
  libavutil      52. 92.100 / 52. 92.100
  libavcodec     55. 69.100 / 55. 69.100
  libavformat    55. 48.100 / 55. 48.100
  libavdevice    55. 13.102 / 55. 13.102
  libavfilter     4. 11.100 /  4. 11.100
  libswscale      2.  6.100 /  2.  6.100
  libswresample   0. 19.100 /  0. 19.100
Input #0, mpeg, from 'demo.mpg':
  Duration: 00:04:19.96, start: 0.000000, bitrate: 1646 kb/s
    Stream #0:0[0x1c0]: Audio: mp2, 44100 Hz, stereo, s16p, 128 kb/s
    Stream #0:1[0x1e0]: Video: mpeg1video, yuv420p(tv), 640x480 [SAR 1:1 DAR 4:3], 104857 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 29.97 tbc
Unknown encoder 'libfaac'

Also I Have Installed libavcodec-extra-54

linux:~$ apt-cache policy libavcodec-extra-54
libavcodec-extra-54:
  Installed: 7:1.2.6-1~trusty1
  Candidate: 7:1.2.6-1~trusty1
  Version table:
 *** 7:1.2.6-1~trusty1 0

I have No Idea What To Do Now To Convert Videos With acodec libfaac

Answer 1

You need to just use aac instead.

ffmpeg -i demo.mpg -acodec aac -strict experimental demo.mp4

Answer 2

Actually use libfdk_aac instead.

ffmpeg -i demo.mpg -acodec libfdk_aac demo.mp4

As to why? Well ffmpeg suggested it to me when playing around with the codecs and getting a list.

Answer 3

Enable your extra repos in /etc/apt/sources.list and then you can find libfaac-dev

edit: you might need to recompile ffmpeg?