FFmpeg has forked and Avconv is more actively developed and so more current.\\
Install it by
<code>
sudo apt-get install libav-tools
</code>
You will then have
  * **Avplay**: a video & audio player.
  * **Avconv**: a multimedia converter plus a video & audio recorder from different sources.
  * **Avprobe**: a tool that connects to the multimedia file stream and returns many useful information and statistics about it.
  * **Libavfilter**: a filtering API for different Libav tools.
Here are some **avconv** examples\\
**Cut a video** : ''avconv -i input.avi -ss 00:27:00 -t 00:58:00 -codec copy output.avi''\\
where
  *''-i'' is input file name, followed by the file name present in the same directory, in this case its, input.avi.
  *''-ss'' is starting time to initialize the cut.
  *''-t'' is the time duration of the video at which you need to stop cutting. It’s not to be confused with the ending position. It is duration from the starting point of the video. Say if your starting position is at 1:03 and you want it to cut at 2:45, you need to enter the difference 1:42 and not 2:45.
  *''-codec copy'' specifies that the output video is not to be re-encoded.
**Crop a video** : ''avconv -i input.avi -vf crop=720:600:0:360 output.flv''

  *''-vf'' is used to specify a selection, say a rectangle to be used from the input video to process.

  *''crop=out_w:out_h:x:y'', this format is to crop the selection from the input. ''out_w'' is the output’s width and ''out_h'' is the output’s height and x and y are the selection to be cropped. So in the example above the cropped video will be ''720px X 600 px'' but aligned from top at 360px. The remaining areas before the 0px X 360px are removed.
**Convert from 1080p to 720p** : ''avconv -i input.mkv -vcodec libx264 -vf scale="trunc(oh*a/2)*2:720" output.mp4''

This performs what one would want with ''-vf scale=-1:720'' syntax (keep original aspect ratio) normally used but somehow doesn't work in my case.

Some useful options\\
  *''-b 512k'' specifies a bitrate of 512k
  *''-vcodec libx264'' specifies using h264 compression
  *''-b:v 600k''
  *''-maxrate 600k'' set maximum bitrate at 600k
  *''-acodec libmp3lame'' specifies the lame mp3 audio encoder
  *''-b:a 128k -c:a libvo_aacenc -ac 2'' specifies the aac encoder at 128K bitrate and stereo sound

**Audio**\\
To convert an audio file to mp3, very simply use\\
<code>
avconv -b 192k -i file file.mp3
</code>
where 192k is the sampling rate

**An example**\\
''avconv -i input.wmv -vcodec libx264 -acodec libmp3lame -ss 00:01:51 -t 00:00:40 -b 1024k output.mp4''\\
''avconv -i input.mkv -vcodec libx264 -b:v 1280k -b:a 128k -c:a libvo_aacenc -ac 2 output.mp4''

**Use a bash script to convert all files in a directory **\\
For instance, to covert all .flac files to .mp3 files, you can use this script
<code>
#!/bin/bash
#flac to mp3 directory converter
find . -iname "*.flac" -exec avconv -i {} -acodec libmp3lame -b 320k {}.mp3 ";" -ls
</code>
This will convert all the .flac files to .flac.mp3\\
To rename all to .mp3, one way is to use Midnight Commander i.e. mc\\
In **mc**, press ''+'' to get the selection box\\
Enter ''*.flac.mp3'' to select all the files to be renamed.\\
Press ''F6'' to get the ''Ren/Mov'' box\\
Put ''*.flac.mp3'' in source and ''*.mp3'' in destination which will rename all *.flac.mp3 files to *.mp3

Or you can use a version of the bash script above, change as required...
<code>
find . -name '*.flac.mp3' -exec sh -c 'mv "$0" "${0%.flac.mp3}.mp3"' {} \;
</code>