converting from .wmv to .mp4

I want to convert some of my videos from .wmv to .mp4. Not only that, I want to make the size of my videos shorter.

Can anyone recommend me any software?

(ubuntu 12.4 + ram 1 gb)

I will be really grateful...

1. Install ffmpeg

   sudo apt-get install ffmpeg
   

2. Convert files like this

   ffmpeg -i input.wmv -s size output.mp4
   

Following size abbreviations are recognized (from man page)

   -s size
       Set frame size. The format is wxh (avserver default = 160x128, ffmpeg default = same as source).  The following abbreviations are recognized:

       sqcif
           128x96

       qcif
           176x144

       cif 352x288

       4cif
           704x576

       16cif
           1408x1152

       qqvga
           160x120

       qvga
           320x240

       vga 640x480

       svga
           800x600

       xga 1024x768

       uxga
           1600x1200

       qxga
           2048x1536

       sxga
           1280x1024

       qsxga
           2560x2048

       hsxga
           5120x4096

       wvga
           852x480

       wxga
           1366x768

       wsxga
           1600x1024

       wuxga
           1920x1200

       woxga
           2560x1600

       wqsxga
           3200x2048

       wquxga
           3840x2400

       whsxga
           6400x4096

       whuxga
           7680x4800

       cga 320x200

       ega 640x350

       hd480
           852x480

       hd720
           1280x720

       hd1080
           1920x1080

Package 'ffmpeg' has no installation candidate ??

Here is solution for it. (I had pasted this solution from link provided above, in order save some time.)

sudo add-apt-repository ppa:mc3man/trusty-media

Also note that with apt-get a sudo apt-get dist-upgrade is needed for initial setup & with some package upgrades
More info: https://launchpad.net/~mc3man/+archive/ubuntu/trusty-media
Press [ENTER] to continue or ctrl-c to cancel adding it


sudo apt-get update
sudo apt-get dist-upgrade

sudo apt-get install ffmpeg

after package get installed

ffmpeg -i input.wmv -c:v libx264 -crf 23 -c:a aac -strict -2 -q:a 100 output.mp4