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Old 05-26-2007, 09:08 AM   #1
Daws
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Start two instances of a program simultaneously using bash


Hello everybody.

I am trying to compare two video files which have been encoded in theora at different quality settings. I am (trying) to use mplayer in konsole(bash). My current method (SMASH! CLICK! SMASH!) leaves the two videos slightly out of sync which makes them difficult to compare. So, does anyone know a way to make bash start two different commands at exactly the same time?

Thanks for any help.
 
Old 05-26-2007, 09:33 AM   #2
osor
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You can probably do something like
Code:
$ mplayer -slave vid1.avi & mplayer vid2.avi
(that should start them very close to simultaneously).

P.S., I can’t help but think there is some program specifically written for comparing two videos side-by-side (if only I could give you a name).

Last edited by osor; 05-26-2007 at 09:45 AM. Reason: Corrected original by adding “-slave”
 
Old 05-26-2007, 09:33 AM   #3
Okie
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maybe this? (no guarantees though)

type in both commands in the same line separated by either && or |
 
Old 05-26-2007, 09:47 AM   #4
osor
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Quote:
Originally Posted by Okie
type in both commands in the same line separated by either && or |
&& represents “AND” and will run the second instance after the first instance (only if the first instance exited successfully).

| represents a pipe, and will run both simultaneously (but the input of the second will be borked/uncontrollable because it will be connected to the output of the first).

& is your most likely best option. It will put the first instance in “the background”, allowing the second instance to run. Of course, mplayer is expecting a terminal for stdin, so you might have to tell it otherwise (i.e., use the “-slave” option).
 
Old 05-26-2007, 01:10 PM   #5
Okie
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thanks Osar...
 
Old 05-26-2007, 01:54 PM   #6
Daws
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Thanks for the replies. As expected && and | do not work. A single & seems to work but they are still a good second out of sync. Am I right in thinking that hardware limitations are now the problem?
 
  


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