CFEXECUTE, FFMPEG and MENCODER - Mystery Solved

I am feeling good today. Why? Because I think I have solved the mystery of how to make cfexecute and ffmpeg and/or mencoder work together on ColdFusion 8. That question has been bugging me for a few weeks now. Now the fact that this problem was really solved Ben Forta, et. al., long before now, is irrelevant ;) I think my perseverance has earned me a gold star anyway.

The Rosetta Stone

In previous entries I described how I was able to use ffmpeg and mencoder with Runtime.exec and cfthread. So far it is working well and one seeming advantage over cfexecute is the ability to kill the process if it exceeds a certain amount of time. But ever curious I still wanted to know if it could be done with cfexecute. Well, thanks to a helpful suggestion from halL on livedocs.adobe.com, and the wisdom of Ben Forta, I have discovered it can be done.

Waiting for Godot

The solution was found in two entries on Ben Forta's blog. The first key was using using /c as an argument. On windows, this "tells the command interpreter to run and terminate upon completion". Otherwise the interpreter may continue to run, waiting endlessly for the signal it should finish.

The second entry mentioned a quirk of cfexecute: it only captures the stdout stream, not stderr. This is important to programs like ffmpeg and mencoder because they write to both streams. According to Forta you can capture both streams by redirecting stderr to stdout. On windows this is done by appending 2>&1 to the end of the command to be executed.

Nirvana (No not *that* Nirvana)

Now I had seen both tips before. I could have sworn I had tried them and they did not work with ffmpeg. I was half-right. The problem was I had used the options separately, not together.

When I tried using the /c flag only, cfexecute timed out. When I examined the Task Manager I could see it left an orphaned cmd.exe and ffmpeg.exe process running. They continued to run until I bounced the CF server.

<!---  
   WARNING!!!
   This code will leave two instances of CMD.exe and
   FFMPEG.EXE running  until the CF server is restarted
--->
<cftry>
   <!--- using a large file and a short timeout value --->
   <cfset argString = '/c d:\bin\ffmpeg.exe -i "d:\bin\testInput.mpg" -g 300 -y -s 300x200 -f flv -ar 44100 "d:\bin\testOuput12.flv"' >
   <cfexecute name="c:\winnt\system32\cmd.exe" arguments="#argString#"    outputFile="d:\bin\results12.log" timeout="120" />

   <cfcatch>
       <cfdump var="#cfcatch#">
   </cfcatch>
</cftry>

Next I tried using the redirect option, but again cfexecute timed out. This time it left behind an orphaned cmd.exe process. Or perhaps I have so many orphaned processes running right now, I have lost track. Whichever processes it left behind, they too remained running until the CF server was restarted.

<!---    
   WARNING!!!
   This code will leave an instance of CMD.exe and
   running until the CF server is restarted
--->

<cftry>
   <!--- using a large file and a short timeout value --->
   <cfset argString = 'd:\bin\ffmpeg.exe -i "d:\bin\testInput.mpg" -g 300 -y -s 300x200 -f flv -ar 44100 "d:\bin\testOuput13.flv" 2>&1' >
   <cfexecute name="c:\winnt\system32\cmd.exe" arguments="#argString#"    outputFile="d:\bin\results13.log" timeout="120" />

   <cfcatch>
       <cfdump var="#cfcatch#">
   </cfcatch>
</cftry>

Finally it hit me. I had not tried using both options together. Doh! So I added the options, clicked my heels three times, muttered an incantation and .. poof! Once I used both the /c and redirect 2>&1 options, ffmpeg and mencoder worked perfectly.

<!---    
   GOOD:  
   Use both the /c flag and the redirect 2>&1 option
--->
<cftry>
   <!--- using a large file and a short timeout value --->
   <cfset argString = '/c d:\bin\ffmpeg.exe -i "d:\bin\testInput.mpg" -g 300 -y -s 300x200 -f flv -ar 44100 "d:\bin\testOuput14.flv" 2>&1' >
   <cfexecute name="c:\winnt\system32\cmd.exe" arguments="#argString#"  
outputFile="d:\bin\results14.log" timeout="120" />

   <cfcatch>
       <cfdump var="#cfcatch#">
   </cfcatch>
</cftry>

Now if for some reason cfexecute times out, it may leave the processes running temporarily. But since we have used the /c flag, they will terminate eventually, once they have completed. That is one reason I am leaning towards the Runtime.exec method over cfexecute. The ability to kill a long running process appeals to me. Though now that I think about it, a "killOnTimeout" attribute might be a nice enhancement of cfexecute. But I will wait to see what future versions bring.

That is it for now. Comments, corrections or suggestions are always welcome. Enjoy!