cron job is not completing the process?

I have a ruby program to convert video to MP4 format using ffmpeg. And I'm using the crontab to run the ruby program every 15 minutes. crontab actually runs the ruby program, but the conversion of the file is not complete. The process is stopped before completing the conversion. My sample code for testin is below.

def convert(y)
 system "ffmpeg -i #{SOURCE_FOLDER + LOCATION_SOURCE}/#{y} -acodec libfaac -ar 44100 -ab 96k -vcodec libx264 #{DEST_FOLDER + LOCATION_DEST}/#{y}"
end
SOURCE_FOLDER = "/home/someone/work/videoapp/public/"
DEST_FOLDER = "/home/someone/work/videoapp/public/"
LOCATION_SOURCE = "source"
LOCATION_DEST = "dest"
files = Dir.new(SOURCE_FOLDER + LOCATION_SOURCE)
files.each do |x|
    convert开发者_运维技巧(x)
end

This code works fine, if i run it manually in the console.

My first guess is that it's dying on "dot" directories. In Unix there are two directories in every directory/folder: "." and "..". You'll either need to specifically skip those in your script:

next if File.directory?(x) # OR
next file x.match(/^\.+$/)

-- OR --

Look specifically for whatever filetypes you are wanting

Dir[SOURCE_FOLDER + LOCATION_SOURCE + "*.wav"].each do |file|
  convert(file)
end

Update: 20110401

Add Unix redirects to the crontab entry to see what the output is

* * * * * /your/program/location/file.rb 1> /some/output/file.txt 2>&1