Resizing

My first thought was that I could use Gimp, but alas it does not by default have a batch conversion process. There is a plug-in called “David’s Batch Processor”, but it doesn’t allow you to specify just the X or Y dimension by itself.

The resizing tool I went for was ‘mogrify‘, which is a command line utility with awesome image manipulation capabilities. Since I wanted to get all my landscape format images down to 400 pixels wide, I just entered the following command:

mogrify -resize 400 *.jpg

For the portrait images that I wanted to all be 400 pixels high I entered:

mogrify -resize x400 *.jpg

Renaming

Once I had all the images resized, I wanted to set the names of my preview thumbnails to end ‘_pre.jpg’. It turns out that this is very easy to do with the ‘rename’ command, which was written by the creator of Perl – Larry Wall. The command is included by default with Debian and Ubuntu, and is easily added to other distros.

Just supply ‘rename’ with a regular expression, and it renames your files as required. The important part of the command parameter is:

's/ [pattern to match] / [what to replace it with] /'

To rename my images I just entered:

rename -v 's/\.jpg$/_pre\.jpg/' *.jpg

To test the command without actually renaming anything, just change ‘-v’ to ‘-n’.

For more information on the ‘rename’ command see http://tips.webdesign10.com/how-to-bulk-rename-files-in-linux-in-the-terminal

For example if you create a new directory with umask set to 022, the resulting permissions are set to 755, since 777 – 022 = 755.

Most of the time umask is set sensibly from the beginning, and you don’t have to worry about it. If you do need to change it, you’ll probably find it being set in one of your login scripts – ‘/etc/profile’ or ‘~/.bashrc’.

For more information just check the man page.

date +%s

at a convenient command line might be faster, and more accurate…

Just run the following command:

lsb_release -a

This should give a result such as the following:

Distributor ID:	Ubuntu
Description:	Ubuntu 8.10
Release:	8.10
Codename:	intrepid

Additionally, to find out what type of architecture your kernel is currently compiled for, just run:

uname -m

Which will give something like this:

x86_64

The projects website is at http://ffmpeg.mplayerhq.hu/. Here’s a few links to some of the most useful parts of the project’s own documentation:

• Supported file, image, video and audio formats
• Video options
• Audio options

The simplest command format is ‘ffmpeg -i inputFile outputFile’, but it can be made as complex as required, in order to specify every single parameter of the conversion process.

To obtain the encoding details from an existing audio or video file, just run the command with only an input file specified, e.g.: ffmpeg -i somefile.avi

I’ll now list some commonly used parameters. These may do exactly what you need first time, but don’t be surprised if you have to tweak the parameters slightly for them to work on your system, with your files:

Convert AVI video to MPEG:

ffmpeg -i inputFile.avi outputFile.mpg

Convert MPEG video to AVI:

ffmpeg -i inputFile.mpg outputFile.avi

Convert FLV to MPEG:

ffmpeg -i inputFile.flv -ab 56k -ar 22050 -b 500k -s 320x240 outputFile.mpg

Audio bit-rate: 56kbps

Audio sampling frequency: 22050Hz

Video bit-rate: 500kbps

Video size: 320 x 240

 
Convert MPEG or AVI to FLV:

ffmpeg -i inputFile.avi -acodec mp3 -ar 22050 -f flv outputFile.flv

Audio sampling frequency: 22050Hz

 
Convert AVI to MPEG-2 for DVD
Note that you will probably need to change the ‘target’ and ‘aspect’ to match your needs:

ffmpeg -i inputFile.avi -target pal-dvd -aspect 16:9 outputFile.mpg

Convert sequence of JPEGs to MPEG:
Note that the image files in this example would named ‘pic-001.jpg, pic-002.jpg, etc…

ffmpeg -f image2 -i pic-%d.jpg outputFile.mpg

Convert MPEG or AVI to sequence of JPEGs:

ffmpeg -i inputFile.mpg pic-%d.jpg

Convert MPEG or AVI to time-lapsed sequence of JPEGs, one per second:

ffmpeg -i inputFile.mpg -r 1 pic-%d.jpg

Video frame-rate: 1fps

 
Convert MPEG or AVI to animated GIF:

ffmpeg -i inputFile.avi outputFile.gif

Convert MP3 to WAV:

ffmpeg -i inputFile.mp3 outputFile.wav

Convert WAV to MP3:

ffmpeg -i inputFile.wav -ab 256k outputFile.mp3

Audio bit-rate: 256kbps

 
Remove the audio from MPEG or AVI:

ffmpeg -i inputFile.avi -an outputFile.avi

Remove video from MPEG or AVI, and convert to MP3:

ffmpeg -i inputFile.avi -an -ab 256k outputFile.mp3

Audio bit-rate: 256kbps

 
Add audio and video together, and convert to MPEG:

ffmpeg -i audioFile.wav -i videoFile.avi outputFile.mpg

The watch command is used to run a given command at a predefined interval, and to monitor the output in real-time until the watch command is terminated. When run, it initially only displays the first output of the given command, and then only updates it if something in the output changes.

For example to have a constantly up-to-date listing of a directory, just run

watch ls

Or similarly to have a list of who is logged onto your system, just run

watch who

These two examples are very simple, but they can be made as complex as you like.

A number of options can be used:

• ‘-d’ or ‘–differences’ will briefly highlight what has changed in the output
• ‘–cumulative’ will make the differences remain displayed
• ‘-n seconds‘ or ‘–interval=seconds‘ will allow the interval between program runs to be set to something other than it default of two seconds

Because it can now running natively on a 64-bit architecture without the aid of a wrapper, it has a smaller memory footprint and is vastly more stable. With the 32-bit version I usually had to restart Firefox at least once a day to free up some RAM, or just to get Flash Player working again.

To get your copy, just go to http://labs.adobe.com/downloads/flashplayer10.html