BASH: Single-Quotes inside a Single-Quoted String

In bash, to escape some characters for the command-line arguments properly, you can use single quotes. E.g.,

$ file 'Some # Weird File Name.odt'

But how about the single quote characters? There are several methods. I found the following ways most convenient.

(1) Replace ' with '\''

Break out of the quoted string, and escape the single quote alone.

 $ file 'My wife'\''s file.txt'

(2) Replace ' with '"'"'

Same idea, but different way of escaping the single quote.

$ file 'My wife'"'"'s file.txt'

So, in Python, you can use:

s = string.replace("'", "'\"'\"'")

or in PHP,

s = str_replace("'", "'\"'\"'", string);

MPlayer & MEncoder: Manipulating Audio Channels

MPlayer provides powerful controls to manipulate different audio channels.

During playback,

• ( and ) keys: Adjust audio balance in favor of left/right channel.
• # key: Cycle through the available audio tracks.

You can add, remove, route, or copy audio channels with the -af channels=nch[:nr:from1:to1:from2:to2:from3:to3:...] option. For example, if there are 2 channels, and you want to copy channel 0 to channel 1 (and thus abandon the original channel 1), you can use -af channels=2:2:0:0:0:1.

You can even mix the channels with specified proportions with the -af pan=... option. Unfortunately, the suboptions are naturally much more complicated. Basically you can specify a 2D matrix to indicate the amount of each source channel that will be mixed to the destination channel.

References:

• man page of mplayer (with very helpful examples.) (Online: http://www.mplayerhq.hu/DOCS/man/en/mplayer.1.html)
• http://www.mplayerhq.hu/DOCS/HTML/en/advaudio-surround.html
• http://www.mplayerhq.hu/DOCS/HTML/en/advaudio-channels.html